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AP®︎/College Biology

Course: ap®︎/college biology   >   unit 7.

  • Introduction to evolution and natural selection
  • Natural selection and the owl butterfly
  • Biodiversity and natural selection
  • Variation in a species

Darwin, evolution, & natural selection

Natural selection, key points:.

  • Charles Darwin was a British naturalist who proposed the theory of biological evolution by natural selection.
  • Darwin defined evolution as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor.
  • The mechanism that Darwin proposed for evolution is natural selection . Because resources are limited in nature, organisms with heritable traits that favor survival and reproduction will tend to leave more offspring than their peers, causing the traits to increase in frequency over generations.
  • Natural selection causes populations to become adapted , or increasingly well-suited, to their environments over time. Natural selection depends on the environment and requires existing heritable variation in a group.

What is evolution?

Early ideas about evolution, influences on darwin, darwin and the voyage of the beagle.

  • Traits are often heritable. In living organisms, many characteristics are inherited, or passed from parent to offspring. (Darwin knew this was the case, even though he did not know that traits were inherited via genes.) A diagram with text reading parents pass on heritable traits to their offspring. On the left a dark blue and a light blue butterfly are crossed to produce offspring with wings of varying shades of blue. On the right a dark red and a light red butterfly are crossed to produce offspring with wings of varying shades of red.
  • More offspring are produced than can survive. Organisms are capable of producing more offspring than their environments can support. Thus, there is competition for limited resources in each generation. A diagram with a box reading limited resources. Arrows point away from the box to bubbles reading lack of food, lack of habitat, and lack of mates. Text below reads …not all individuals will survive and reproduce. A group of 16 butterflies with wings of varying shades of blue and red is shown. A text bubble reading gleep! comes from 4 of the butterflies.
  • Offspring vary in their heritable traits. The offspring in any generation will be slightly different from one another in their traits (color, size, shape, etc.), and many of these features will be heritable. A group of 16 butterflies with wings of varying shades of blue and red is shown. A text bubble reading Hey, are you red? That's pretty sweet! comes from one of the blue butterflies. A text bubble reading Whoa! Love that blue wing color comes from one of the red butterflies. Text at the bottom reads Butterflies do not actually talk! Cartoon for cute illustration purposes only. A smiley face is shown next to the text.
  • In a population, some individuals will have inherited traits that help them survive and reproduce (given the conditions of the environment, such as the predators and food sources present). The individuals with the helpful traits will leave more offspring in the next generation than their peers, since the traits make them more effective at surviving and reproducing.
  • Because the helpful traits are heritable, and because organisms with these traits leave more offspring, the traits will tend to become more common (present in a larger fraction of the population) in the next generation.
  • Over generations, the population will become adapted to its environment (as individuals with traits helpful in that environment have consistently greater reproductive success than their peers).

Example: How natural selection can work

Key points about natural selection, natural selection depends on the environment, natural selection acts on existing heritable variation, heritable variation comes from random mutations, natural selection and the evolution of species, attribution:, works cited:.

  • Wilkin, D. and Akre, B. (2016, March 23). Influences on Darwin - Advanced. In CK-12 biology advanced concepts . Retrieved from http://www.ck12.org/book/CK-12-Biology-Advanced-Concepts/section/10.18/ .
  • Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). The voyage of the Beagle . In Campbell Biology (10th ed., p. 466). San Francisco, CA: Pearson.
  • Darwin's finches. (2016, April 25). Retrieved March 16, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Darwin%27s_finches .
  • Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Figure 1.18. Natural selection. In Campbell biology (10th ed., p. 14). San Francisco, CA: Pearson.

Additional references:

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essay on charles darwin theory of evolution

Charles Darwin: Evolutionary Theory Explained

Charles Darwin, a name synonymous with the theory of evolution, revolutionized our understanding of the natural world. His observations and insights laid the foundation for evolutionary biology, challenging existing views on species origin and development. This article explores Darwin’s life, the formulation of his groundbreaking theory, and its profound impact on science and society.

Early Life and Influences

Born on February 12, 1809, in Shrewsbury, England, Charles Darwin was the fifth of six children in a wealthy and well-connected family. His father, Robert Darwin, was a successful physician, and his grandfather, Erasmus Darwin, was a noted intellectual who had hinted at evolutionary ideas himself. Despite this rich intellectual heritage, Charles did not initially show a strong interest in academics, often preferring the natural world.

Darwin enrolled at Edinburgh University to study medicine but soon found he could not stomach the brutality of surgery at the time. This aversion led him to Cambridge University, where he intended to become a clergyman. However, it was at Cambridge that Darwin’s true passion for natural science began to flourish. He was profoundly influenced by botany professor John Stevens Henslow and geologist Adam Sedgwick, who exposed him to contemporary scientific thought and field research.

The Voyage of the Beagle

Darwin’s life changed dramatically in 1831 when he was invited to join the HMS Beagle as a naturalist on a five-year voyage around the world. This journey would provide him with unique opportunities to observe natural phenomena. From the volcanic archipelagos of the Galapagos to the coral reefs of Australia, Darwin collected a plethora of natural specimens, including fossils, birds, animals, and plants.

Throughout his travels, Darwin observed variations that species exhibited across different geographical areas, particularly noting how island species appeared to have diverged from mainland species. The pivotal moment came in the Galapagos Islands, where Darwin noticed that the finches on each island differed mainly in beak shape, tailored to their specific dietary needs.

Development of Evolutionary Theory

After returning to England in 1836, Darwin began to synthesize his observations into a coherent theory of how species evolve. Influenced by Thomas Malthus’s essay on population growth, Darwin proposed that species evolve through a process he called natural selection. He suggested that individuals with traits that enhance their ability to adapt to their environment are more likely to survive and reproduce. Over generations, these traits become more common in the population, leading to evolutionary changes.

Darwin worked on his theory for over 20 years, collecting extensive evidence and cautiously refining his arguments. He corresponded with numerous scientists and conducted breeding experiments, particularly with pigeons, to understand more about inheritance and variation.

Publication and Reaction

The publication of Darwin’s “On the Origin of Species by Means of Natural Selection” in 1859 marked a turning point in biological science and public discourse. The book argued convincingly for the evolution of species by natural processes, challenging the prevailing belief of special creation that was widely held at the time.

The reaction to Darwin’s ideas was mixed. The scientific community was initially skeptical but gradually came to accept the evidence. The broader public reaction included both interest and outrage, particularly from religious groups who saw Darwin’s ideas as conflicting with the literal interpretation of the creation stories in the Bible.

Legacy and Continuing Impact

Darwin’s theory of evolution by natural selection became a fundamental concept in biology, influencing a wide range of scientific disciplines. His ideas paved the way for the modern understanding of genetic inheritance, species diversification, and ecological interactions. Today, evolutionary biology not only helps us understand the history of life on Earth but also provides essential insights into conservation, agriculture, and medicine.

Despite controversies and challenges over the years, the core of Darwinian evolutionary theory remains robust, supported by discoveries in genetics, paleontology, and molecular biology. The ongoing research in evolutionary biology continually reaffirms and refines Darwin’s initial insights.

Charles Darwin’s development of evolutionary theory represents one of the most significant achievements in scientific history. His work transformed how we comprehend the biological world, emphasizing the dynamic and interconnected nature of life. Darwin’s legacy continues to influence both scientific thought and cultural perspectives on human existence and the natural environment, underscoring the power of observation, evidence-based thinking, and the courage to challenge conventional wisdom.

essay on charles darwin theory of evolution

The Broader Implications of Darwin’s Work

Beyond biology, Darwin’s theory of evolution had broad implications across multiple fields, including psychology, sociology, and ethics, challenging and enriching our understanding of human behavior and social structures. It influenced thinkers like Herbert Spencer, who coined the term “survival of the fittest,” mistakenly extending Darwinian ideas into social and economic realms, a concept now known as social Darwinism.

Evolutionary Theory in Modern Science

Today, evolutionary theory continues to be a cornerstone of modern biology. It provides the framework for understanding the complex relationships between all living things, from the smallest bacteria to the largest mammals, including humans. It helps scientists understand the spread of diseases, the development of antibiotic resistance, and the principles behind biological diversity.

The field of genetics, in particular, has expanded our understanding of evolution. The discovery of DNA and the mechanisms of genetic inheritance have provided detailed evidence supporting and expanding Darwinian theory. This molecular perspective confirms the connections among species that Darwin inferred from morphology and biogeography.

The Evolution of Evolutionary Thought

Darwin’s initial ideas have also evolved. While natural selection remains central, other mechanisms such as genetic drift, gene flow, and mutation are now known to play significant roles in the evolution of species. Modern synthesis, a 20th-century development that integrates Darwin’s theory with genetic principles, has further solidified and expanded the theoretical framework of evolution, confirming its status as one of the most robust theories in science.

Darwin’s Cultural and Social Impact

Culturally, Darwin’s work has continued to provoke thought, debate, and reflection on human origins, our place in the natural world, and the ethics of how we relate to other living beings. These discussions have permeated various aspects of culture and society, from education and politics to religion and philosophy.

In education, Darwin’s theories are now fundamental components of biology curricula across the world, although they continue to face opposition in some regions for religious and ideological reasons. Politically and ethically, the implications of Darwin’s work have sparked debates on topics ranging from conservation policies to bioethical considerations in genetics and medicine.

Challenges and Controversies

Despite its scientific acceptance, evolutionary theory has faced and continues to face significant challenges. Some of these challenges come from within the scientific community itself, where new evidence can lead to adjustments and refinements of the theory. Others come from outside the scientific realm, particularly from ideological viewpoints that oppose the idea of evolution on religious or moral grounds.

Public misconceptions about what evolution is and what it implies are also widespread, often fueled by misunderstandings about the nature of scientific theories and evidence. This has led to ongoing public debates, particularly in the context of educational curricula and scientific literacy.

Looking Forward

As we look to the future, the principles of evolutionary biology will remain crucial as we tackle new challenges from environmental changes and shifts in global biodiversity to advances in genetic engineering and biotechnology. Understanding evolution helps predict changes in ecosystems and assists in managing everything from endangered species to pest resistances.

The evolution of evolutionary theory, pioneered by Charles Darwin, remains a testament to the power of scientific inquiry and evidence-based understanding. Darwin’s legacy is not merely in the specifics of his findings but also in his methodological approach and his unwavering commitment to a rational explanation for natural phenomena. As we continue to explore the biological sciences, the principles he established serve as guideposts for ongoing discoveries and remind us of our interconnectedness with the natural world.

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Darwin: From the Origin of Species to the Descent of Man

This entry offers a broad historical review of the origin and development of Darwin’s theory of evolution by natural selection through the initial Darwinian phase of the “Darwinian Revolution” up to the publication of the Descent of Man in 1871. The development of evolutionary ideas before Darwin’s work has been treated in the separate entry evolutionary thought before Darwin . Several additional aspects of Darwin’s theory of evolution and his biographical development are dealt with in other entries in this encyclopedia (see the entries on Darwinism ; species ; natural selection ; creationism ). The remainder of this entry will focus on aspects of Darwin’s theory not developed in the other entries. It will also maintain a historical and textual approach. Other entries in this encyclopedia cited at the end of the article and the bibliography should be consulted for discussions beyond this point. The issues will be examined under the following headings:

1.1 Historiographical Issues

1.2 darwin’s early reflections, 2.1. the concept of natural selection.

  • 2.2. The Argument of the Published Origin

3.1 The Popular Reception of Darwin’s Theory

3.2 the professional reception of darwin’s theory, 4.1 the genesis of darwin’s descent, 4.2 darwin on mental powers, 4.3 the ethical theory of the descent of man.

  • 4.4 The Reception of the Descent

5. Summary and Conclusion

Other internet resources, related entries, acknowledgments, 1. the origins of darwin’s theory.

Charles Darwin’s version of transformism has been the subject of massive historical and philosophical scholarship almost unparalleled in any other area of the history of science. This includes the continued flow of monographic studies and collections of articles on particular aspects of Darwin’s theory (Prestes 2023; R. J. Richards and Ruse 2016; Ruse 2013a, 2009a,b,c; Ruse and Richards 2009; Hodge and Radick 2009; Hösle and Illies 2005; Gayon 1998; Bowler 1996; Depew and Weber 1995; Kohn 1985a). The continuous production of popular and professional biographical studies on Darwin provides ever new insights (Ruse et al. 2013a; Johnson 2012; Desmond and Moore 1991, 2009; Browne 1995, 2002; Bowlby 1990; Bowler 1990). In addition, major editing projects on Darwin’s manuscripts and the completion of the Correspondence , project through the entirety of Darwin’s life, continue to reveal details and new insights into the issues surrounding Darwin’s own thought (Keynes [ed.] 2000; Burkhardt et al. [eds] 1985–2023; Barrett et al. [eds.] 1987). The Cambridge Darwin Online website (see Other Internet Resources ) serves as an international clearinghouse for this worldwide Darwinian scholarship, functioning as a repository for electronic versions of all the original works of Darwin, including manuscripts and related secondary materials. It also supplies a continuously updated guide to current literature.

A long tradition of scholarship has interpreted Darwin’s theory to have originated from a framework defined by endemic British natural history, a British tradition of natural theology defined particularly by William Paley (1743–1805), the methodological precepts of John Herschel (1792–1871), developed in his A Preliminary Discourse on the Study of Natural Philosophy (1830 [1987]), and the geological theories of Charles Lyell (1797–1875). His conversion to the uniformitarian geology of Charles Lyell and to Lyell’s advocacy of “deep” geological time during the voyage of the HMS Beagle (December 1831–October 1836), has been seen as fundamental in his formation (Norman 2013; Herbert 2005; Hodge 1983). Complementing this predominantly anglophone historiography has been the social-constructivist analyses emphasizing the origins of Darwin’s theories in British Political Economy (Young 1985: chps. 2, 4, 5). It has also been argued that a primary generating source of Darwin’s inquiries was his involvement with the British anti-slavery movement, a concern reaching back to his revulsion against slavery developed during the Beagle years (Desmond and Moore 2009).

A body of recent historiography, on the other hand, drawing on the wealth of manuscripts and correspondence that have become available since the 1960s (online at Darwin online “Papers and Manuscripts” section, see Other Internet Resources ) has de-emphasized some of the novelty of Darwin’s views and questions have been raised regarding the validity of the standard biographical picture of the early Darwin. These materials have drawn attention to previously ignored aspects of Darwin’s biography. In particular, the importance of his Edinburgh period from 1825–27, largely discounted in importance by Darwin himself in his late Autobiography , has been seen as critical for his subsequent development (Desmond and Moore 1991; Hodge 1985). As a young medical student at the University of Edinburgh (1825–27), Darwin developed a close relationship with the comparative anatomist Robert Edmond Grant (1793–1874) through the student Plinian Society, and in many respects Grant served as Darwin’s first mentor in science in the pre- Beagle years (Desmond and Moore 1991, chp. 1). Through Grant he was exposed to the transformist theories of Jean Baptiste Lamarck and the Cuvier-Geoffroy debate centered on the Paris Muséum nationale d’histoire naturelle (see entry on evolutionary thought before Darwin , Section 4).

These differing interpretive frameworks make investigations into the origins of Darwin’s theory an active area of historical research. The following section will explore these origins.

In its historical origins, Darwin’s theory was different in kind from its main predecessors in important ways (Ruse 2013b; Sloan 2009a; see also the entry on evolutionary thought before Darwin ). Viewed against a longer historical scenario, Darwin’s theory does not deal with cosmology or the origins of the world and life through naturalistic means, and therefore was more restricted in its theoretical scope than its main predecessors influenced by the reflections of Georges Louis LeClerc de Buffon (1707–1788), Johann Herder (1744–1803, and German Naturphilosophen inspired by Friederich Schelling (1775–1854) . This restriction also distinguished Darwin’s work from the grand evolutionary cosmology put forth anonymously in 1844 by the Scottish publisher Robert Chambers (1802–1871) in his immensely popular Vestiges of the Natural History of Creation , a work which in many respects prepared Victorian society in England, and pre-Civil War America for the acceptance of a general evolutionary theory in some form (Secord 2000; MacPherson 2015). It also distinguishes Darwin’s formulations from the theories of his contemporary Herbert Spencer (1820–1903).

Darwin’s theory first took written form in reflections in a series of notebooks begun during the latter part of the Beagle voyage and continued after the return of the Beagle to England in October of 1836 (Barrett et al., 1987). His reflections on the possibility of species change are first entered in March of 1837 (“Red Notebook”) and are developed in the other notebooks (B–E) through July of 1839 (Barrett et al. 1987; Hodge 2013a, 2009). Beginning with the reflections of the third or “D” “transmutation” Notebook, composed between July and October of 1838, Darwin first worked out the rudiments of what was to become his theory of natural selection. In the parallel “M” and “N” Notebooks, dating between July of 1838 and July of 1839, and in a loose collection called “Old and Useless Notes”, dating from approximately 1838–40, he also developed many of his main ideas on human evolution that would only be made public in the Descent of Man of 1871 (below, Section 4).

To summarize a complex issue, these Notebook reflections show Darwin proceeding through a series of stages in which he first formulated a general theory of the transformation of species by historical descent from common ancestors. He then attempted to work out a causal theory of life that would explain the tendency of life to complexify and diversify (Hodge 2013a, 2009, 1985; Sloan 1986). This causal inquiry into the underlying nature of life, and with it the search for an explanation of life’s innate tendency to develop and complexify, was then replaced by a dramatic shift in focus away from these inquiries. This concern with a causal theory of life was then replaced by a new emphasis on external forces controlling population, a thesis developed from his reading of Thomas Malthus’s (1766–1834) Essay on the Principle of Population (6th ed. 1826). For Malthus, human populaton was assumed to expand geometrically, while food supply expanded arithmetically, leading to an inevitable struggle of humans for existence. The impact of Darwin’s reading of this edition of the Essay in August of 1838, was dramatic. It enabled him to theorize the existence of a constantly-acting dynamic force behind the transformation of species.

Darwin’s innovation was to universalize the Malthusian “principle of population” to apply to all of nature. In so doing, Darwin effectively introduced what may be termed an “inertial” principle into his theory, although such language is never used in his text. Newton’s first law of motion, set forth in his Mathematical Principles of Natural Philosophy (1st ed. 1687), established his physical system upon the tendency of all material bodies to persist eternally either at rest or in uniform motion in a straight line, requiring a causal force explanation for any deviations from this initial state. But Newton did not seek a deeper metaphysical explanation of this inertial state. Law One is simply an “axiom” in Newton’s Principia. Similarly, the principle of population supplied Darwin with the assumption of an initial dynamic state of affairs that was not itself explained within the theory—there is no attempt to account causally for this tendency of living beings universally to reproduce geometrically. Similarly for Darwin, the principle of population functions axiomatically, defining a set of initial conditions from which any deviance from this ideal state demands explanation.

This theoretical shift enabled Darwin to bracket his earlier efforts to develop a causal theory of life, and focus instead on the means by which the dynamic force of population was controlled. This allowed him to emphasize how controls on population worked in company with the phenomenon of slight individual variation between members of the same species, in company with changing conditions of life, to produce a gradual change of form and function over time, leading to new varieties and eventually to new species. This opened up the framework for Darwin’s most important innovation, the concept of “natural” selection.

2. Darwinian Evolution

The primary distinguishing feature of Darwin’s theory that separates it from previous explanations of species change centers on the causal explanation he offered for how this process occurred. Prior theories, such as the theory of Jean-Baptiste Lamarck (see entry on evolutionary thought before Darwin ), relied on the inherent dynamic properties of matter. The change of species was not, in these pre-Darwinian efforts, explained through an adaptive process. Darwin’s emphasis after the composition of Notebook D on the factors controlling population increase, rather than on a dynamic theory of life grounded in vital forces, accounts for many of the differences between Darwin’s theory and those of his predecessors and contemporaries.

These differences can be summarized in the concept of natural selection as the central theoretical component of Darwinian theory. However, the exact meaning of this concept, and the varying ways he stated the principle in the Origin over its six editions (1859–1872), has given rise to multiple interpretations of the meaning of this principle in the history of Darwinism, and the different understandings of his meaning deeply affected different national and cultural receptions of his theory (see below, Section 3 .1).

One way to see the complexity of Darwin’s own thinking on these issues is to follow the textual development of this concept from the close of the Notebook period (1839) to the publication of the Origin of Species in 1859. This period of approximately twenty years involved Darwin in a series of reflections that form successive strata in the final version of his theory of the evolution of species. Understanding the historical sequence of these developments also has significance for subsequent controversies over this concept and the different readings of the Origin as it went through its successive revisions. This historical development of the concept also has some bearing on assessing Darwin’s relevance for more general philosophical questions, such as those surrounding the relevance of his theory for such issues as the concept of a more general teleology of nature.

The earliest set of themes in the manuscript elaboration of natural selection theory can be characterized as those developed through a particular form of the argument from analogy. This took the form of a strong “proportional” form of the analogical argument that equated the relation of human selection to the development of domestic breeds as an argument of the basic form: human selection is to domestic variety formation as natural selection is to natural species formation (White, Hodge and Radick 2021, chps. 4–5). This makes a direct analogy between the actions of nature with those of humans in the process of selection. The specific expressions, and changes, in this analogy are important to follow closely. As this was expressed in the first coherent draft of the theory, a 39-page pencil manuscript written in 1842, this discussion analogized the concept of selection of forms by human agency in the creation of the varieties of domestic animals and plants, to the active selection in the natural world by an almost conscious agency, a “being infinitely more sagacious than man (not an omniscient creator)” who acts over “thousands and thousands of years” on “all the variations which tended towards certain ends” (Darwin 1842 in Glick and Kohn 1996, 91). This agency selects out those features most beneficial to organisms in relation to conditions of life, analogous in its action to the selection by man on domestic forms in the production of different breeds. Interwoven with these references to an almost Platonic demiurge are appeals to the selecting power of an active “Nature”:

Nature’s variation far less, but such selection far more rigid and scrutinizing […] Nature lets <<an>> animal live, till on actual proof it is found less able to do the required work to serve the desired end, man judges solely by his eye, and knows not whether nerves, muscles, arteries, are developed in proportion to the change of external form. (Ibid., 93)

These themes were continued in the 230 page draft of his theory of 1844. Again he referred to the selective action of a wise “Being with penetration sufficient to perceive differences in the outer and innermost organization quite imperceptible to man, and with forethought extending over future centuries to watch with unerring care and select for any object the offspring of an organism produced” (Darwin 1844 in ibid., 101). This selection was made with greater foresight and wisdom than human selection. As he envisions the working of this causal agency,

In accordance with the plan by which this universe seems governed by the Creator, let us consider whether there exist any secondary means in the economy of nature by which the process of selection could go on adapting, nicely and wonderfully, organisms, if in ever so small a degree plastic, to diverse ends. I believe such secondary means do exist. (Ibid., 103).

Darwin returned to these issues in 1856, following a twelve-year period in which he published his Geological Observations on the Volcanic Islands (1844), the second edition of his Journal of Researches (1845), Geological Observations on South America (1846), the four volumes on fossil and living barnacles ( Cirripedia ) (1851, 54, 55), and Geological Observations on Coral Reefs (1851). In addition, he published several smaller papers on invertebrate zoology and on geology, and reported on his experiments on the resistance of seeds to salt water, a topic that would be of importance in his explanation of the population of remote islands.

These intervening inquiries positioned Darwin to deal with the question of species permanence against an extensive empirical background. The initial major synthesis of these investigations takes place in his long manuscript, or “Big Species Book”, commenced in 1856, known in current scholarship as the “Natural Selection” manuscript. This formed the immediate background text behind the published Origin . Although incomplete, the “Natural Selection” manuscript provides insights into many critical issues in Darwin’s thinking. It was also prepared with an eye to the scholarly community. This distinguishes its content and presentation from that of the subsequent “abstract” which became the published Origin of Species . “Natural Selection” contained tables of data, references to scholarly literature, and other apparatus expected of a non-popular work, none of which appeared in the published Origin .

The “Natural Selection” manuscript also contained some new theoretical developments of relevance to the concept of natural selection that are not found in earlier manuscripts. Scholars have noted the introduction in this manuscript of the “principle of divergence”, the thesis that organisms under the action of natural selection will tend to radiate and diversify within their “conditions of life”—the contemporary name for the complex of environmental and species-interaction relationships (Kohn 1985b, 2009). Although the concept of group divergence under the action of natural selection might be seen as an implication of Darwin’s theory from his earliest formulations of the 1830s, nonetheless Darwin’s explicit definition of this as a “principle”, and its discussion in a long late insertion in the “Natural Selection” manuscript, suggests its importance for Darwin’s mature theory. The principle of divergence was now seen by Darwin to form an important link between natural variation and the conditions of existence under the action of the driving force of population increase.

Still evident in the “Natural Selection” manuscript is Darwin’s implicit appeal to some kind of teleological ordering of the process. The action of the masculine-gendered “wise being” of the earlier manuscripts, however, has now been given over entirely to the action of a selective “Nature”, now referred to in the traditional feminine gender. This Nature,

…cares not for mere external appearance; she may be said to scrutinise with a severe eye, every nerve, vessel & muscle; every habit, instinct, shade of constitution,—the whole machinery of the organisation. There will be here no caprice, no favouring: the good will be preserved & the bad rigidly destroyed.… Can we wonder then, that nature’s productions bear the stamp of a far higher perfection than man’s product by artificial selection. With nature the most gradual, steady, unerring, deep-sighted selection,—perfect adaption [sic] to the conditions of existence.… (Darwin 1856–58 [1974: 224–225])

The language of this passage, directly underlying statements about the action of “natural selection” in the first edition of the published Origin , indicates the complexity in the exegesis of Darwin’s meaning of “natural selection” when viewed in light of its historical genesis (Ospovat 1981). The parallels between art and nature, the intentionality implied in the term “selection”, the notion of “perfect” adaptation, and the substantive conception of “nature” as an agency working toward certain ends, all render Darwin’s views on teleological purpose more complex than they are typically interpreted from the standpoint of contemporary Neo-selectionist theory (Lennox 1993, 2013). As will be discussed below, the changes Darwin subsequently made in his formulations of this concept over the history of the Origin have led to different conceptions of what he meant by this principle.

The hurried preparation and publication of the Origin between the summer of 1858 and November of 1859 was prompted by the receipt on June 18 of 1858 of a letter and manuscript from Alfred Russel Wallace (1823–1913) that outlined his remarkably similar views on the possibility of continuous species change under the action of a selection upon natural variation (Wallace 1858 in Glick and Kohn 1996, 337–45). This event had important implications for the subsequent form of Darwin’s published argument. Rapidly condensing the detailed arguments of the unfinished “Natural Selection” manuscript into shorter chapters, Darwin also universalized several claims that he had only developed with reference to specific groups of organisms, or which he had applied only to more limited situations in the manuscript. This resulted in a presentation of his theory at the level of broad generalization. The absence of tables of data, detailed footnotes, and references to the secondary literature in the published version also resulted in predictable criticisms which will be discussed below in Section 3.2 .

2.2. The Central Argument of the Published Origin

The Origin of Species by Means of Natural Selection, or the Preservaton of Favoured Races in the Struggle for Life was issued in London by the publishing house of John Murray on November 24, 1859 (Darwin 1859 [1964]). The structure of the argument presented in the published Origin has been the topic of considerable literature and can only be summarized here. Although Darwin himself described his book as “one long argument”, the exact nature of this argument is not immediately transparent, and alternative interpretations have been made of his reasoning and rhetorical strategies in formulating his evolutionary theory. (Prestes 2023; White, Hodge and Radick 2021; Hodge 2013b, 1977; Hoquet 2013; Hull 2009; Waters 2009; Depew 2009; Ruse 2009; Lennox 2005; Hodge 1983b).

The scholarly reconstruction of Darwin’s methodology employed in the Origin has taken two primary forms. One approach has been to reconstruct it from the standpoint of currently accepted models of scientific explanation, sometimes presenting it as a formal deductive model (Sober 1984). Another, more historical, approach interprets his methodology in the context of accepted canons of scientific explanation found in Victorian discussions of the period (see the entry on Darwinism ; Prestes 2023; White, Hodge and Radick 2021; Hodge 2013b, 1983b, 1977; Hoquet 2013; Hull 2009; Waters 2009; Depew 2009; Lennox 2005). The degree to which Darwin did in fact draw from the available methodological discussions of his contemporaries—John Herschel, William Whewell, John Stuart Mill—is not fully clear from available documentary sources. The claim most readily documented, and defended particularly by White, Hodge and Radick (2021) and M. J. S. Hodge (1977, 1983a), has emphasized the importance of John Herschel’s A Preliminary Discourse on the Study of Natural Philosophy (1830 [1987]), which Darwin read as a young student at Cambridge prior to his departure on the HMS Beagle in December of 1831.

In Herschel’s text he would have encountered the claim that science seeks to determine “true causes”— vera causae— of phenomena through the satisfaction of explicit criteria of adequacy (Herschel, 1830 [1987], chp. 6). This concept Newton had specified in the Principia as the third of his “Rules of Reasoning in Philosophy” (see the entry on Newton’s philosophy , Section 4). Elucidation of such causes was to be the goal of scientific explanation. Vera causae , in Herschel’s formulation, were those necessary to produce the given effects; they were truly active in producing the effects; and they adequately explained these effects.

The other plausible methodological source for Darwin’s mature reasoning was the work of his older contemporary and former Cambridge mentor, the Rev. William Whewell (1794–1866), whose three-volume History of the Inductive Sciences (Whewell 1837) Darwin read with care after his return from his round-the-world voyage (Ruse 2013c, 1975). On this reading, a plausible argument has been made that the actual structure of Darwin’s text is more closely similar to a “Whewellian” model of argument. In Whewell’s accounts of his philosophy of scientific methodology (Whewell 1840, 1858), the emphasis of scientific inquiry is, as Herschel had also argued, to be placed on the discovery of “true causes”. But evidence for the determination of a vera causa was to be demonstrated by the ability of disparate phenomena to be drawn together under a single unifying “Conception of the Mind”, exemplified for Whewell by Newton’s universal law of gravitation. This “Consilience of Inductions”, as Whewell termed this process of theoretical unification under a few simple concepts, was achieved only by true scientific theories employing true causes (Whewell 1840: xxxix). It has therefore been argued that Darwin’s theory fundamentally produces this kind of consilience argument, and that his methodology is more properly aligned with that of Whewell.

A third account, related to the Whewellian reading, is that of David Depew. Building on Darwin’s claim that he was addressing “the general naturalist public,” Darwin is seen as developing what Depew has designated as “situated argumentation”, similar to the views developed by contemporary Oxford logician and rhetorical theorist Richard Whately (1787–1863) (Depew 2009). This rhetorical strategy proceeds by drawing the reader into Darwin’s world by personal narration as it presents a series of limited issues for acceptance in the first three chapters, none of which required of the reader a considerable leap of theoretical assent, and most of which, such as natural variation and Malthusian population increase, had already been recognized in some form in the literature of the period.

As Darwin presented his arguments to the public, he opens with a pair of chapters that draw upon the strong analogy developed in the manuscripts between the action of human art in the production of domestic forms, and the actions of selection “by nature.” The resultant forms are presumed to have arisen through the action of human selection on the slight variations existing between individuals within the same species. The interpretation of this process as implying directional, and even intentional, selection by a providential “Nature” that we have seen in the manuscripts was, however, downplayed in the published work through the importance given by Darwin to the role of “unconscious” selection, a concept not encountered in the Natural Selection manuscript. Such selection denotes the practice even carried out by aboriginal peoples who simply seek to maintain the integrity and survival of a breed or species by preserving the “best” forms.

The domestic breeding analogy is, however, more than a decorative rhetorical strategy. It repeatedly functions for Darwin as the principal empirical example to which he could appeal at several places in the text as a means of visualizing the working of natural selection in nature, and this appeal remains intact through the six editions of the Origin.

From this model of human selection working on small individual natural variations to produce the domestic forms, Darwin then developed in the second chapter the implications of “natural” variation, delaying discussion of the concept of natural selection until Chapter IV. The focus of the second chapter introduces another important issue. Here he extends the discussion of variation developed in Chapter I into a critical analysis of the common understanding of classification as grounded on the definition of species and higher groups based on the possession of essential defining properties. It is in this chapter that Darwin most explicitly develops his own position on the nature of organic species in relation to his theory of descent. It is also in this chapter that he sets forth the ingredients for his attack on one meaning of species “essentialism”.

Darwin’s analysis of the “species question” involves a complex argument that has many implications for how his work was read by his contemporaries and successors, and its interpretation has generated a considerable literature (see the entries on species and Darwinism ; Mallet 2013; R. A. Richards 2010; Wilkins 2009; Stamos 2007; Sloan 2009b, 2013; Beatty 1985).

Prior tradition had been heavily affected by eighteenth-century French naturalist Buffon’s novel conception of organic species in which he made a sharp distinction between “natural” species, defined primarily by fertile interbreeding, and “artificial” species and varieties defined by morphological traits and measurements upon these (see the entry on evolutionary thought before Darwin , Section 3.3). This distinction was utilized selectively by Darwin in an unusual blending of two traditions of discussion that are conflated in creative ways in Darwin’s analysis.

Particularly as the conception of species had been discussed by German natural historians of the early nineteenth-century affected by distinctions introduced by philosopher Immanuel Kant (1724–1804), “Buffonian” species were defined by the material unity of common descent and reproductive continuity. This distinguished them by their historical and material character from the taxonomic species of the “Linnean” tradition of natural history. This distinction between “natural” and “logical” species had maintained a distinction between problems presented in the practical classification of preserved specimens, distinguished by external characters, and those relating to the unity of natural species, which was grounded upon reproductive unity and the sterility criterion (Sloan 2009b).

Remarkable in Darwin’s argument is the way in which he draws selectively in his readings from these two preexistent traditions to undermine the different grounds of species “realism” assumed within both of these traditions of discourse. One framework—what can be considered in his immediate context the “Linnean” tradition—regarded species in the sense of universals of logic or class concepts, whose “reality” was often grounded on the concept of divine creation. The alternative “Buffonian” tradition viewed species more naturalistically as material lineages of descent whose continuity was determined by some kind of immanent principle, such as the possession of a conserving “internal mold” or specifying vital force (see evolutionary thought before Darwin 3.3). The result in Darwin’s hands is a complex terminological interweaving of concepts of Variety, Race, Sub-species, Tribe, and Family that can be shown to be a fusion of different traditions of discussion in the literature of the period. This creative conflation also led to many confusions among his contemporaries about how Darwin actually did conceive of species and species change in time.

Darwin addresses the species question by raising the problems caused by natural variation in the practical discrimination of taxa at the species and varietal levels, an issue with which he had become closely familiar in his taxonomic revision of the Sub-class Cirripedia (barnacles) in his eight-year study on this group. Although the difficulty of taxonomic distinctions at this level was a well-recognized problem in the literature of the time, Darwin subtly transforms this practical problem into a metaphysical ambiguity—the fuzziness of formal taxonomic distinctions created by variation in preserved specimens is seen to imply a similar ambiguity of “natural” species boundaries.

We follow this in reading how natural variation is employed by Darwin in Chapter Two of the Origin to break down the distinction between species and varieties as these concepts were commonly employed in the practical taxonomic literature. The arbitrariness apparent in making distinctions, particularly in plants and invertebrates, meant that such species were only what “naturalists having sound judgment and wide experience” defined them to be ( Origin 1859 [1964], 47). These arguments form the basis for claims by his contemporaries that Darwin was a species “nominalist”, who defined species only as conventional and convenient divisions of a continuum of individuals.

But this feature of Darwin’s discussion of species captures only in part the complexity of his argument. Drawing also on the tradition of species realism developed within the “Buffonian” tradition, Darwin also affirmed that species and varieties are defined by common descent and material relations of interbreeding. Darwin then employed the ambiguity of the distinction between species and varieties created by individual variation in practical taxonomy to undermine the ontological fixity of “natural” species. Varieties are not simply the formal taxonomic subdivisions of a natural species as conceived in the Linnaean tradition. They are, as he terms them, “incipient” species (ibid., 52). This subtly transformed the issue of local variation and adaptation to circumstances into a primary ingredient for historical evolutionary change. The full implications to be drawn from this argument were, however, only to be revealed in Chapter Four of the text.

Before assembling the ingredients of these first two chapters, Darwin then introduced in Chapter Three the concept of a “struggle for existence”. This concept is introduced in a “large and metaphorical sense” that included different levels of organic interactions, from direct struggle for food and space to the struggle for life of a plant in a desert. Although described as an application of Thomas Malthus’s parameter of geometrical increase of population in relation to the arithmetical increase of food supply, Darwin’s use of this concept in fact reinterprets Malthus’s principle, which was formulated only with reference to human population in relation to food supply. It now becomes a general principle governing all of organic life. Thus all organisms, including those comprising food for others, would be governed by the tendency to geometrical increase.

Through this universalization, the controls on population become only in the extreme case grounded directly on the traditional Malthusian limitations of food and space. Normal controls are instead exerted through a complex network of relationships of species acting one on another in predator-prey, parasite-host, and food-web relations. This profound revision of Malthus’s arguments rendered Darwin’s theory deeply “ecological” as this term would later be employed. We can cite two thought experiments employed by Darwin himself as illustrations (ibid., 72–74). The first concerns the explanation of the abundance of red clover in England. This Darwin sees as dependent on the numbers of pollinating humble bees, which are controlled in turn by the number of mice, and these are controlled by the number of cats, making cats the remote determinants of clover abundance. The second instance concerns the explanation of the abundance of Scotch Fir. In this example, the number of fir trees is limited indirectly by the number of cattle.

With the ingredients of the first three chapters in place, Darwin was positioned to assemble these together in his grand synthesis of Chapter Four on “natural” selection. In this long discussion, Darwin develops the main exposition of his central theoretical concept. For his contemporaries and for the subsequent tradition, however, the meaning of Darwin’s concept of “natural” selection was not unambiguously evident for reasons we have outlined above, and these unclarities were to be the source of several persistent lines of disagreement and controversy.

The complexities in Darwin’s presentation of his central principle over the six editions of the published Origin served historically to generate several different readings of his text. In the initial introduction of the principle of natural selection in the first edition of Darwin’s text, it is characterized as “preservation of favourable variations and the rejection of injurious variations” (ibid., 81). When Darwin elaborated on this concept in Chapter Four of the first edition, he continued to describe natural selection in language suggesting that it involved intentional selection, continuing the strong art-nature analogy found in the manuscripts. For example:

As man can produce and certainly has produced a great result by his methodical and unconscious means of selection, what may not nature effect? Man can act only on external and visible characters: nature cares nothing for appearances, except in so far as they may be useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends. Every selected character is fully exercised by her; and the being is placed under well-suited conditions of life. (Ibid., 83)

The manuscript history behind such passages prevents the simple discounting of these statements as mere rhetorical imagery. As we have seen, the parallel between intentional human selectivity and that of “nature” formed the proportional analogical model upon which the concept of natural selection was originally constructed.

Criticisms that quickly developed over the overt intentionality embedded in such passages, however, led Darwin to revise the argument in editions beginning with the third edition of 1861. From this point onward he explicitly downplayed the intentional and teleological language of the first two editions, denying that his appeals to the selective role of “nature” were anything more than a literary figure. Darwin then moved decisively in the direction of defining natural selection as the description of the action of natural laws working upon organisms rather than as an efficient or final cause of life. He also regrets in his Correspondence his mistake in not utilizing the designation “natural preservation” rather than “natural selection” to characterize his principle (letter to Lyell 28 September 1860, Burkhardt Correspondence 8, 397; also see Darwin Correspondence Project in Other Internet Resources ). In response to criticisms of Alfred Russel Wallace, Darwin then adopted in the fifth edition of 1869 his contemporary (1820–1903) Herbert Spencer’s designator, “survival of the fittest”, as a synonym for “natural selection” (Spencer 1864, 444–45; Darwin 1869, 72). This redefinition further shifted the meaning of natural selection away from the concept that can be extracted from the early texts and drafts. These final statements of the late 1860s and early 70s underlie the tradition of later “mechanistic” and non-teleological understandings of natural selection, a reading developed by his disciples who, in the words of David Depew, “had little use for either his natural theodicy or his image of a benignly scrutinizing selection” (Depew 2009, 253). The degree to which this change preserved the original strong analogy between art and nature can, however, be questioned. Critics of the use of this analogy had argued since the original formulations that the comparison of the two modes of selection actually worked against Darwin’s theory (Wallace 1858 in Glick and Kohn 1997, 343). This critique would also be leveled against Darwin in the critical review of 1867 by Henry Fleeming Jenkin discussed below.

The conceptual synthesis of Chapter Four also introduced discussions of such matters as the conditions under which natural selection most optimally worked, the role of isolation, the causes of the extinction of species, and the principle of divergence. Many of these points were made through the imaginative use of “thought experiments” in which Darwin constructed possible scenarios through which natural selection could bring about substantial change.

One prominent way Darwin captured for the reader the complexity of this process is reflected in the single diagram to appear in all the editions of the Origin . In this illustration, originally located as an Appendix to the first edition, but thereafter moved into Chapter Four, Darwin summarized his conception of how species were formed and diverged from common ancestral points. This image also served to depict the frequent extinction of most lineages, an issue developed in detail in Chapter Ten. It displayed pictorially the principle of divergence, illustrating the general tendency of populations to diverge and fragment under the pressure of population increase. It supplied a way of envisioning relations of taxonomic affinity to time, and illstrated the persistence of some forms unchanged over long geological periods in which stable conditions prevail.

Graph labeled on the horizontal-axis with the letters A to L and on the vertical-axis with Roman numerals I to XIV. From A branch up several dashed lines; all but two stop before reaching vertical-level I; from those two branch up several more dashed lines, some stop before the next vertical-level those that don't sprout up more lines, repeat though in some cases no line from a particular branch reaches the next vertical-level. Further description in the text following.

Figure: Tree of life diagram from Origin of Species ( Origin 1859:“Appendix”.

Remarkable about Darwin’s diagram of the tree of life is the relativity of its coordinates. It is first presented as applying only to the divergences taking place in taxa at the species level, with varieties represented by the small lower-case letters within species A–L of a “wide ranging genus”, with the horizontal lines representing time segments measured in terms of a limited number of generations. However, the attentive reader could quickly see that Darwin’s destructive analysis of the distinction between “natural” and “artificial” species in Chapter Two, implied the relativity of the species-variety distinction, this diagram could represent eventually all organic relationships, from those at the non-controversial level of diverging varieties within fixed species, to those of the relations of Species within different genera. Letters A–L could also represent taxa at the level of genera, families or orders. The diagram can thus be applied to relationships between all levels of the Linnaean hierarchy with the time segments representing potentially vast expanses of time, and the horizontal spread of branches the degree of taxonomic divergence over time. In a very few pages of argument, the diagram was generalized to represent the most extensive group relations, encompassing the whole of geological time. Extension of the dotted lines at the bottom could even suggest, as Darwin argues in the last paragraph of the Origin , that all life was a result of “several powers, having been originally breathed into a few forms or into one” (Darwin 1859 [1964], 490). This could suggest a single naturalistic origin of all original forms either by material emergence, or through the action of a vitalistic power of life. Darwin’s use of Biblical language could also be read as allowing for the action of a supernatural cause.

In response to criticisms concerning this latter point, Darwin quickly added to the final paragraph in the second edition of 1860 the phrase “by the Creator” (1860: 484), which remained in all subsequent editions. as did the quotations on the frontispiece from familiar discussions in British natural theology concerning creation by secondary causation. Conceptual space was thereby created for the reading of the Origin by some contemporaries, notably by the Harvard botanist Asa Gray (1810–88), as compatible with traditional natural theology (Gray 1860).

The sweep of the theoretical generalization that closed the natural selection chapter, one restated even more generally in the final paragraph of the book, required Darwin to deal with several obvious objections to the theory that constitute the main “defensive” chapters of the Origin (Five–Nine), and occupy him through the numerous revisions of the text between 1859 and 1872. As suggested by David Depew, the rhetorical structure of the original text developed in an almost “objections and response” structure that resulted in a constant stream of revisions to various editions of the original text as Darwin engaged his opponents (Depew 2009; Peckham 2006). Anticipating at first publication several obvious lines of objection, Darwin devoted much of the text of the original Origin to offering a solution in advance to predictable difficulties. As Darwin outlined these main lines of objection, he discussed, first, the apparent absence of numerous slight gradations between species, both in the present and in the fossil record, of the kind that would seem to be predictable from the gradualist workings of the theory (Chps. Six, Nine). Second, the gradual development of organs and structures of extreme complexity, such as the vertebrate eye, an organ which had since Antiquity served as a mainstay of the argument for external teleological design (Chp. Six). Third, the evolution of the elaborate instincts of animals and the puzzling problem of the evolution of social insects that developed sterile neuter castes, proved to be a particularly difficult issue for Darwin in the manuscript phase of his work and needed some account (Chp. Seven). As a fourth major issue needing attention, the traditional distinction between natural species defined by interfertility, and artificial species defined by morphological differences, required an additional chapter of analysis in which he sought to undermine the absolute character of the interbreeding criterion as a sign of fixed natural species (Chp. Eight).

In Chapter Ten, Darwin developed his interpretation of the fossil record. At issue was the claim by Lamarckian and other transformists, as well as Cuvierian catastrophists such as William Buckland (1784–1856) (see the entry on evolutionary thought before Darwin , Section 4.1), that the fossil record displayed a historical sequence beginning with simpler plants and animals, arriving either by transformism or replacement, at the appearance of more complex forms in geological history. Opposition to this thesis of “geological progressionism” had been made by none other than Darwin’s great mentor in geology, Charles Lyell in his Principles of Geology (Lyell 1832 [1990], vol. 2, chp. xi; Desmond 1984; Bowler 1976). Darwin defended the progressionist view against Lyell’s arguments in this chapter.

To each of the lines of objection to his theory, Darwin offered his contemporaries plausible replies. Additional arguments were worked out through the insertion of numerous textual insertions over the five revisions of the Origin between 1860 and 1872, including the addition of a new chapter to the sixth edition dealing with “miscellaneous” objections, responding primarily to the criticisms of St. George Jackson Mivart (1827–1900) developed in his Genesis of Species (Mivart 1871).

For reasons related both to the condensed and summary form of public presentation, and also as a reflection of the bold conceptual sweep of the theory, the primary argument of the Origin could not gain its force from the data presented by the book itself. Instead, it presented an argument from unifying simplicity, gaining its force and achieving assent from the ability of Darwin’s theory to draw together in its final synthesizing chapters (Ten–Thirteen) a wide variety of issues in taxonomy, comparative anatomy, paleontology, biogeography, and embryology under the simple principles worked out in the first four chapters. This “consilience” argument might be seen as the best reflection of the impact of William Whewell’s methodology (see above).

As Darwin envisioned the issue, with the acceptance of his theory, “a grand untrodden field of inquiry will be opened” in natural history. The long-standing issues of species origins, if not the the explanation of the ultimate origins of life, as well as the causes of their extinction, had been brought within the domain of naturalistic explanation. It is in this context that he makes the sole reference in the text to the claim that “light will be thrown on the origin of man and his history”. And in a statement that will foreshadow the important issues of the Descent of Man of 1871, he speaks of how “Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation” (ibid., 488)

3. The Reception of the Origin

The broad sweep of Darwin’s claims, the brevity of the empirical evidence actually supplied in the Origin , and the implications of his theory for several more general philosophical and theological issues, opened up a controversy over Darwinian evolution that has waxed and waned over more than 160 years. The theory was inserted into a complex set of different national and cultural receptions the study of which currently forms a scholarly industry in its own right. European, Latin American and Anglophone receptions have been most deeply studied (Bowler 2013a; Gayon 2013; Largent 2013; Glick 1988, 2013; Glick and Shaffer 2014; Engels and Glick 2008; Gliboff 2008; Numbers 1998; Pancaldi, 1991; Todes 1989; Kelly 1981; Hull 1973; Mullen 1964). To these have been added analyses of non-Western recptions (Jin 2020, 2019 a,b; Yang 2013; Shen 2016; Elshakry 2013; Pusey 1983). These analyses display common patterns in both Western and non-Western readings of Darwin’s theory, in which these receptions were conditioned, if not determined, by the pre-existing intellectual, scientific, religious, social, and political contexts into which his works were inserted.

In the anglophone world, Darwin’s theory fell into a complex social environment that in the United States meant into the pre-Civil War slavery debates (Largent 2013; Numbers 1998). In the United Kingdom it was issued against the massive industrial expansion of mid-Victorian society, and the development of professionalized science. To restrict focus to aspects of the British reading public context, the pre-existing popularity of the anonymous Vestiges of the Natural History of Creation of 1844, which had reached 11 editions and sold 23,350 copies by December of 1860 (Secord “Introduction” to Chambers 1844 [1994], xxvii]), with more editions to appear by the end of the century, certainly prepared the groundwork for the general notion of the evolutionary origins of species by the working of secondary natural laws. The Vestiges ’s grand schema of a teleological development of life, from the earliest beginnings of the solar system in a gaseous nebula to the emergence of humanity under the action of a great “law of development”, had also been popularized for Victorian readers by Alfred Lord Tennyson’s epic poem In Memoriam (1850). This Vestiges backdrop provided a context in which some could read Darwin as supplying additional support for the belief in an optimistic historical development of life under teleological guidance of secondary laws with the promise of ultimate historical redemption. Such readings also rendered the Origin seemingly compatible with the progressive evolutionism of Darwin’s contemporary Herbert Spencer (see the entry on Herbert Spencer ). Because of these similarities, Spencer’s writings served as an important vehicle by which Darwin’s views, modified to fit the progressivist views expounded by Spencer, were first introduced in non-Western contexts (Jin 2020, 2019 a,b; Lightman [ed.] 2015; Pusey 1983). Such popular receptions ignored or revised Darwin’s concept of evolution by natural selection to fit these progressivist alternatives.

Outside the United Kingdom, the receptions of Darwin’s work display the importance of local context and pre-existent intellectual and social conditions. Three examples—France, Germany, and China—can be elaborated upon. In France, Darwin’s theory was received against the background of the prior debates over transformism of the 1830s that pitted the theories of Lamarck and Etienne Geoffroy St. Hilaire against Cuvier (Gayon 2013; entry on evolutionary thought before Darwin , 4.1). At least within official French Academic science, these debates had been resolved generally in favor of Cuvier’s anti-transformism. The intellectual framework provided by the “positive philosophy” of Auguste Comte (1798–1857) also worked both for and against Darwin. On one hand, Comte’s emphasis on the historical progress of science over superstition and metaphysics allowed Darwin to be summoned in support of a theory of the progress of science. The Origin was so interpreted in the preface to the first French translation of the Origin made by Clémence Royer (Harvey 2008). On the other hand, the Comtean three stages view of history, with its claim of the historical transcendence of speculative and metaphysical periods of science by a final period of experimental science governed by determinate laws, placed Darwinism in a metaphysical phase of speculative nature philosophy. This view is captured by the assessment of the leading physiologist and methodologist of French Science, Claude Bernard (1813–78). As he stated this in his 1865 treatise on scientific methodology, Darwin’s theory was to be regarded with those of “a Goethe, an Oken, a Carus, a Geoffroy Saint Hilaire”, locating it within speculative philosophy of nature rather than granting it the status of “positive” science (Bernard 1865 [1957], 91–92]).

In the Germanies, Darwin’s work entered a complex social, intellectual and political situation in the wake of the failed efforts to establish a liberal democracy in 1848. It also entered an intellectual culture strongly influenced by the pre-existent philosophical traditions of Kant, Schelling’s Naturphilosophie , German Romanticism, and the Idealism of Fichte and Hegel (R. J. Richards 2002, 2008, 2013; Gliboff 2007, 2008; Mullen 1964). These factors formed a complex political and philosophical environment into which Darwin’s developmental view of nature and theory of the transformation of species was quickly assimilated, if also altered. Many readings of Darwin consequently interpreted his arguments against the background of Schelling’s philosophy of nature. The marshalling of Darwin’s authority in debates over scientific materialism were also brought to the fore by the enthusiastic advocacy of Darwinism in Germany by University of Jena professor of zoology Ernst Heinrich Haeckel (1834–1919). More than any other individual, Haeckel made Darwinismus a major player in the polarized political and religious disputes of Bismarckian Germany (R. J. Richards 2008). Through his polemical writings, such as the Natural History of Creation (1868), Anthropogeny (1874), and Riddle of the Universe (1895–99), Haeckel advocated a materialist monism in the name of Darwin, and used this as a stick with which to beat traditional religion. Much of the historical conflict between religious communities and evolutionary biology can be traced back to Haeckel’s polemical writings, which went through numerous editions and translations, including several English and American editions that appeared into the early decades of the twentieth century.

To turn to a very different context, that of China, Darwin’s works entered Chinese discussions by a curious route. The initial discussions of Darwinian theory were generated by the translation of Thomas Henry Huxley’s 1893 Romanes Lecture “Evolution and Ethics” by the naval science scholar Yan Fu (1854–1921), who had encountered Darwinism while being educated at the Royal Naval College in Greenwich from 1877 to 1879. This translation of Huxley’s lecture, published in 1898 under the name of Tianyan Lun , was accompanied with an extensive commentary by Yan Fu that drew heavily upon the writings of Herbert Spencer which Yan Fu placed in opposition to the arguments of Huxley. This work has been shown to have been the main vehicle by which the Chinese learned indirectly of Darwin’s theory (Jin 2020, 2019 a, b; Yang 2013; Pusey 1983). In the interpretation of Yan Fu and his allies, such as Kan Yuwei (1858–1927), Darwinism was given a progressivist interpretation in line with aspects of Confucianism.

Beginning in 1902, a second phase of Darwinian reception began with a partial translation of the first five chapters of the sixth edition of the Origin by the Chinese scientist, trained in chemistry and metallurgy in Japan and Germany, Ma Junwu (1881–1940). This partial translation, published between 1902 and 1906, again modified the text itself to agree with the progressive evolutionism of Spencer and with the progressivism already encountered in Yan Fu’s popular Tianyan Lun. Only in September of 1920 did the Chinese have Ma Junwu’s full translation of Darwin’s sixth edition. This late translation presented a more faithful rendering of Darwin’s text, including an accurate translation of Darwin’s final views on natural selection (Jin 2019 a, b). As a political reformer and close associate of democratic reformer Sun Yat-Sen (1866–1925), Ma Junwu’s interest in translating Darwin was also was involved with his interest in revolutionary Chinese politics (Jin 2019a, 2022).

The reception of the Origin by those who held positions of professional research and teaching positions in universities, leadership positions in scientific societies, and employment in museums, was complex. These individuals were typically familiar with the empirical evidence and the technical scientific issues under debate in the 1860s in geology, comparative anatomy, embryology, biogeography, and classification theory. This group can usually be distinguished from lay interpreters who may not have made distinctions between the views of Lamarck, Chambers, Schelling, Spencer, and Darwin on the historical development of life.

If we concentrate attention on the reception by these professionals, Darwin’s work received varied endorsement (Hull 1973). Many prominent members of Darwin’s immediate intellectual circle—Adam Sedgwick, William Whewell, Charles Lyell, Richard Owen, and Thomas Huxley—had previously been highly critical of Chambers’s Vestiges in the 1840s for its speculative character and its scientific incompetence (Secord 2000). Darwin himself feared a similar reception, and he recognized the substantial challenge facing him in convincing this group and the larger community of scientific specialists with which he interacted and corresponded widely. With this group he was only partially successful.

Historical studies have revealed that only rarely did members of the scientific elites accept and develop Darwin’s theories exactly as they were presented in his texts. Statistical studies on the reception by the scientific community in England in the first decade after the publication of the Origin have shown a complicated picture in which there was neither wide-spread conversion of the scientific community to Darwin’s views, nor a clear generational stratification between younger converts and older resisters, counter to Darwin’s own predictions in the final chapter of the Origin (Hull et al. 1978). These studies also reveal a distinct willingness within the scientific community to separate acceptance of Darwin’s more general claim of species descent with modification from common ancestors from the endorsement of his explanation of this descent through the action of natural selection on slight morphological variations.

Of central importance in analyzing this complex professional reception was the role assigned by Darwin to the importance of normal individual variation as the source of evolutionary novelty. As we have seen, Darwin had relied on the novel claim that small individual variations—the kind of differences considered by an earlier tradition as merely “accidental”—formed the raw material upon which, by cumulative directional change under the action of natural selection, major changes could be produced sufficient to explain the origin and subsequent differences in all the various forms of life over time. Darwin, however, left the specific causes of this variation unspecified beyond some effect of the environment on the sexual organs. Variation was presented in the Origin with the statement that “the laws governing inheritance are quite unknown” (Darwin 1859 [1964], 13). In keeping with his commitment to the gradualism of Lyellian geology, Darwin also rejected the role of major “sports” or other sources of discontinuous change in this process.

As critics focused their attacks on the claim that such micro-differences between individuals could be accumulated over time without natural limits, Darwin began a series of modifications and revisions of the theory through a back and forth dialogue with his critics that can be followed in his revisions to the text of the Origin . In the fourth edition of 1866, for example, Darwin inserted the claim that the continuous gradualism depicted by his branching diagram was misleading, and that transformative change does not necessarily go on continuously. “It is far more probable that each form remains for long periods unaltered, and then again undergoes modification” (Darwin 1866, 132; Peckham 2006, 213). This change-stasis-change model allowed variation to stabilize for a period of time around a mean value from which additional change could then resume. Such a model would, however, presumably require even more time for its working than the multi-millions of years assumed in the original presentation of the theory.

The difficulties in Darwin’s arguments that had emerged by 1866 were highlighted in a lengthy and telling critique in 1867 by the Scottish engineer Henry Fleeming Jenkin (1833–1885) (typically Fleeming Jenkin). Using an argument previously raised in the 1830s by Charles Lyell against Lamarck, Fleeming Jenkin cited empirical evidence from domestic breeding that suggested a distinct limitation on the degree to which normal variation could be added upon by selection (Fleeming Jenkin 1867 in Hull 1973). Using a loosely mathematical argument, Fleeming Jenkin argued that the effects of intercrossing would continuously swamp deviations from the mean values of characters and result in a tendency of the variation in a population to return to mean values over time. It is also argued that domestic evidence does not warrant an argument for species change. For Fleeming Jenkin, Darwin’s reliance on continuous additive deviation was presumed to be undermined by these arguments, and only more dramatic and discontinuous change—something Darwin explicitly rejected—could account for the origin of new species.

Fleeming Jenkin also argued that the time needed by Darwin’s theory to account for the history of life under the gradual working of natural selection was simply unavailable from scientific evidence, supporting this claim by an appeal to the physical calculations of the probable age of the solar system presented in publications by his mentor, the Glasgow physicist William Thompson (Lord Kelvin, 1824–1907) (Burchfield 1975). On the basis of Thompson’s quantitative physical arguments concerning the age of the sun and solar system, Fleeming Jenkin judged the time since the presumed first beginnings of life to be insufficient for the Darwinian gradualist theory of species transformation to have taken place.

Jenkin’s multi-pronged argument gave Darwin considerable difficulties and set the stage for more detailed empirical inquiries into variation and its causes by Darwin’s successors. The time difficulties were only resolved in the twentieth-century with the discovery of radioactivity that could explain why the sun did not lose heat in accord with Newtonian principles.

As a solution to the variation question, Darwin developed his “provisional hypothesis” of pangenesis, which he presented the year after the appearance of the Fleeming Jenkin review in his two-volume Variation of Plants and Animals Under Domestication (Darwin 1868; Olby 2013). Although this theory had been formulated independently of the Jenkin review (Olby 1963), in effect it functioned as Darwin’s reply to Jenkin’s critique. The pangenesis theory offered a causal theory of variation and inheritance through a return to a theory resembling Buffon’s theory of the organic molecules proposed in the previous century (see entry on evolutionary thought before Darwin section 3.2). Invisible material “gemmules” were presumed to exist within the cells. According to theory, these were subject to external alteration by the environment and other external causes. The gemmules were then shed continually into the blood stream (the “transport” hypothesis) and assembled by “mutual affinity for each other, leading to their aggregation either into buds or into the sexual elements” (Darwin 1868, vol. 2, 375). In this form they were then transmitted—the details were not explained—by sexual generation to the next generation to form the new organism out of “the modified physiological units of which the organism is built” (ibid., 377). In Darwin’s view, this hypothesis united together numerous issues into a coherent and causal theory of inheritance and explained the basis of variation. It also explained how use-disuse inheritance, a theory which Darwin never abandoned, could work.

The pangenesis theory, although not specifically referred to, seems to be behind an important distinction Darwin inserted into the fifth edition of the Origin of 1869 in his direct reply to the criticisms of Jenkin. In this textual revision, Darwin distinguished “certain variations, which no one would rank as mere individual differences”, from ordinary variations (Darwin1869, 105; Peckham 2006, 178–179). This revision shifted Darwin’s emphasis away from his early reliance on normal slight individual variation, and gave new status to what he now termed “strongly marked” variations. The latter were now the forms of variation to be given primary evolutionary significance. Presumably this strong variation was more likely to be transmitted to the offspring, although details are left unclear, and in this form major variation could presumably be maintained in a population against the tendency to swamping by intercrossing as Fleeming Jenkin had argued.

Darwin’s struggles over this issue defined a set of problems that British life scientists in particular were to deal with into the 1930s. These debates over the role of somatic variation in the evolutionary process placed Darwinism in a defensive posture that forced its supporters into major revisions in the Darwinian research program (Gayon 1998; Vorzimmer 1970). The consequence was a complex period of Darwinian history in which natural selection theory was rejected by many research, or defended in modified form by others (Bowler 1983, 2013a; Largent 2009).

4. Human Evolution and the Descent of Man

Darwin had retained his own conclusions on human evolution quietly in the background through the 1860’s while the defense of his general theory was conducted by advocates as diverse as Thomas Henry Huxley (1825–95) in England, Asa Gray (1810–88) in the United States, and Ernst Haeckel (1834–1919) in the emerging new Germany. Darwin’s own position on the “human question” remained unclear to the reading public, and his rhetorical situating of the Origin within a tradition of divine creation by secondary law, captured in the frontispiece quotations from William Whewell and Francis Bacon, allowed many before 1871 to see Darwin as more open to religious interpretations of human origins than those of some of his popularizers.

Darwin’s interest in developing his insights into the origins of human beings and the explanation of human properties through descent with modification was, however, evident in his correspondence as early as January of 1860 when he began collecting evidence on the expressions of the emotions in human beings (Browne 2002, chp. 9). He then developed a questionnaire specifically intended to gain such information from contacts in Patagonia and Tierra del Fuego (Radick 2018). Further engagement with these issues was then generated by the discussions of Lyell (1863) and A. R. Wallace (1864), both of whom suggested that natural selection could not account for the development of the “higher” rational faculties, language, and ethical motivation (R. J. Richards 1987, chp. 4). It was then in February of 1867 that Darwin decided to remove material from his massive manuscript of the Variation of Plants and Animals Under Domestication to create a “very small volume, ‘an essay on the origin of mankind’” (Darwin to Hooker, 8 February 1867 and CD to Turner, 11 February 1867, Burkhardt, Correspondence 15: 74, 80). At this time he also sent to several international correspondents a more detailed questionnaire asking for information on human emotional expression. Further impetus to develop his views was created by the arguments of William R. Greg (1809–1881) in an essay in Fraser’s Magazine (1868), with further support by arguments of A. R. Wallace in 1869, both of whom drew a sharp distinction between human properties and those of animals (R. J. Richards 1987, 172–184). These arguments denied that natural selection could explain the origins of these “higher powers”.

Darwin’s drafting of his views on human issues, begun in early 1868, expanded into a major enterprise in which he became deeply engaged with the issue of the implications of his theory for ethics. The result of this effort devoted to anthropological topics was two separate works: the Descent of Man and Selection in Relation to Sex , delivered to the publisher in June of 1870 with publication in 1871, and its companion, Expression of the Emotions in Man and Animals , which he commenced in early 1871 with publication in early 1872.

As commentators have noted, these two works differ markedly in their arguments, and reflect different relationships to Darwin’s causal theories of natural and sexual selection, with sexual selection predominting over natural selection for the major portion of the Descent , and both of these causal theories generally missing from the descriptive approach of the Expression (Radick 2018).

Sexual selection—the choosing of females by males or vice versa for breeding purposes—had received a general statement by Darwin in Chapter IV of the Origin , but this played only a minor role in the original argument, and its importance was denied by co-evolutionist A. R. Wallace. In the Descent this was now developed in extensive detail as a major factor in evolution that could even work against ordinary natural selection. Sexual selection could be marshaled to explain sexual dimorphism, and also the presence of unusual characters and properties of organisms—elaborate feeding organs, bright colors, and other seemingly maladaptive structures such as the antlers on the Irish Elk or the great horn on the Rhinoceros beetle—that would appear anomalous outcomes of ordinary natural selection working for the optimal survival of organisms in nature. In a dramatic extension of the principle to human beings, the combination of natural and sexual selection is used to explain the origins of human beings from simian ancestors. It also accounts for the sexual dimorphism in humans, and is a major factor accounting for the origin of human races (E. Richards 2017; R. A. Richards 2013).

Although the secondary causal role of sexual selection in the development of species generally was to be the main topic of the bulk of the Descent , this plays an ambiguous role initially in the “treatise on man” that occupies the initial chapters, and functions differently in his treatment of the origins of mental powers, the moral sense, and the origin of races in this opening discussion.

In constructing this presentation, Darwin reaches back to the early Notebooks that he had separated out from the “transformist” discussions to deal with his inquiries into ethics, psychology, and emotions (see Section 1.2 above). Of particular importance for the opening discussions of the Descent was the “M” notebook, commenced in July of 1838, and “N”, begun in October of that year. On occasion he also samples the collection of entries now entitled “Old and Useless Notes”, generally written between 1838 and 1840.

The initial topic of focus in the Descent deals with the far-reaching issues concerning the status and origin of human mental properties, faculties presumed traditionally to be possessed uniquely by human beings. These properties Darwin now places on an evolutionary continuum with those features of animal behavior long regarded as instinctual. In this he placed himself in opposition to the long tradition of discourse that had distinguished humans from animals due to the possession of a “rational principle” related to their possession of a rational soul. This tradition had been given a more radical foundation in the revolutionary reflections on the relation of mind and body initiated by René Descartes (1596–1650) in the middle of the seventeenth century. Descartes deepened this distinction with the separation of the two substances—thinking substance, or res cogitans , possessed only by humans, and extended material substance, res extensa that constituted the rest of the natural world, including animals and plants, rendering animals only lifeless machines without rational faculties.

Darwin’s collapse of this Cartesian barrier with his theory of human origins outlined in the Descent continued a discussion that had been a concern of his transformist predecessors, especially Jean Baptiste Lamarck (Sloan 1999). But Darwin took this issue to a new level as he interpreted the human-animal relationship in the context of his novel theory of divergent evolution from common ancestors. Darwin also broke with the view of humans as the summit of a natural teleological process. Darwin instead denies such teleological ordering, and effectively reduces human properties to those of animals—mental as well as physical—by tracing them to their origin in properties of lower organisms.

The warrant for the identification of human and animal mental properties, however, is not supported by substantial argumentation in the Descent. The opening discussions of the treatise summarize the anatomical evidence for “homologies” —true identities—between humans and animals due to descent from common ancestors, claims already set out in Chapter Thirteen of the Origin. But the transferal of this identity of structure to inner non-anatomical “mental” properties rested on premises that are not made explicit in this text, and were not identities drawn by Huxley, Wallace and Lyell, for example, in their treatments of humans in relation to evolutionary theory, although they acknowledged the anatomical continuities.

To understand Darwin’s arguments, it is useful to return to his Notebook discussions on which he was drawing for his reasoning (see above, Section 1.2). In his “C” Notebook, opened in February of 1838, Darwin has a remarkable entry that displays very early on his commitment to a metaphysical “monism”—the thesis that there is only one substance underlying both mind and body. With this goes the thesis of a parallelism of the complexity of mental properties with those of material structure. In this entry in “C” following on Darwin’s reflections on the issue of instinct, and also recording some of his observations on animals at the Regents Park zoological gardens, Darwin comments:

There is one living spirit, prevalent over this wor[l]d, (subject to certain contingencies of organic matter & chiefly heat), which assumes a multitude of forms <<each having acting principle>> according to subordinate laws.—There is one thinking […] principle (intimately allied to one kind of organic matter—brain. & which <prin> thinking principle. seems to be given or assumed according to a more extended relations [ sic ] of the individuals, whereby choice with memory, or reason ? is necessary.—) which is modified into endless forms, bearing a close relation in degree & kind to the endless forms of the living beings.— We see thus Unity in thinking and acting principle in the various shades of <dif> separation between those individuals thus endowed, & the community of mind, even in the tendency to delicate emotions between races, & recurrent habits in animals.— (Barrett 1987, 305)

As we follow these issues into the “M” Notebook, the assumption of a single “thinking principle,” allied to one kind of organic matter, seems then to underlie Darwin’s subsequent reflections on mind and matter. The “M” Notebook cites numerous “mental”properties common to humans and animals that generally parallel levels of material organization, similar to the identities expressed in the later Descent. The range of this universal extension of mental properties is far-reaching in these early discussions: consciousness and “free will” extends to all animals, including invertebrates:

With respect to free will, seeing a puppy playing cannot doubt that they have free will, if so all animals., then an oyster has & a polype (& a plant in some senses […]; now free will of oyster, one can fancy to be direct effect of organization, by the capacities its senses give it of pain or pleasure, if so free will is to mind, what chance is to matter […] (Barrett 1987, 536).

When these themes reappear in Chapter Two of the first edition of the Descent , Darwin seems to draw implicitly upon this matter-mind identity theory as an obvious consequence of his theory of descent from common ancestry. There he enumerates a long list of traditional human mental and emotional properties to claim that each of them are identities with the properties of simpler forms of life. The list is expansive: courage, deceit, play, kindness, maternal affection, self-complacency, pride, shame, sense of honor, wonder, dread, imitation, imagination, and dreaming. All are considered to be represented in a wide range of animals, with “play”and “recognition” found even in the ants.

When he addresses the more complex mental properties that specifically had been considered by a long tradition of discussion to be the distinctive human properties—possession of language, reason, abstract conceptual thinking, self-reflection—these again are treated as having their manifestations in other forms of life, with none of them unique to human beings. Language, the property that Descartes, for example, had considered to be the primary distinguishing character denoting the human possession of mind as distinct from matter, Darwin treats a developing in a gradual process from animal sounds that parallel the differentiation of species, illustrated by the fact that languages “like organic beings, can be classed in groups under groups” (Darwin 1871 [1981], 60). He closes his discussion of mental powers with an analysis of religious belief that derives it from imagination and belief in spirits found in aboriginal peoples. It can even be homologized with the “deep love of a dog for his master, associated with complete submissions, some fear, and perhaps other feelings” (ibid., 68). Darwin’s discussions of the relation of human and animal mental and emotional properties would set the agenda for a complex discussion that would carry into contemporary debates over animal cognition and the relations of human and animal properties (see the entries on animal cognition ; methods in comparative cognition ; and animal consciousness ).

The subsequent treatment of ethical issues in the third chapter of the Descent was for Darwin a topic to be approached “exclusively from the side of natural history” (ibid., 71). This issue also presented him with some of his most difficult conceptual problems (CD to Gray, 15 March 1870, Burkhardt, Correspondence 18, 68). In this discussion he also employs natural selection theory as an explanatory cause.

Under the heading of “Moral Sense”, Darwin offered some innovations in ethics that do not easily map on to standard ethical positions classified around the familiar categories of Rule or Act Utilitarianism, Kantian Deontology, Hedonism, and Emotivism. Darwin’s closest historical affinities are with the Scottish “Moral Sense” tradition of Frances Hutcheson (1694–1746), Adam Smith (1723?–1790), and David Hume (1711–1776). More immediately Darwin drew from the expositions of the moral sense theory by his distant relative, Sir James Macintosh (1765–1832) (R. J. Richards 1987, 114–122, 206–219).

Traditional moral sense theory linked ethical behavior to an innate property that was considered to be universal in human beings, although it required education and cultivation to reach its full expression (see the entry on moral sentimentalism ). This inherent property, or “moral” sense, presumably explained such phenomena as ethical conscience, the sense of moral duty, and it accounted for altruistic actions that could not be reduced to hedonic seeking of pleasure and avoiding pain. It also did not involve the rational calculation of advantage, or the maximization of greatest happiness by an individual prior to action, as implied by Utilitarianism. For this reason Darwin criticized John Stuart Mill’s version of Utilitarian theory because it relied on acquired habits and the calculation of advantage (Darwin 1871 [1981], 71n5).

Darwin’s reinterpretation of the moral sense tradition within his evolutionary framework also implied important transfomations of this theory of ethics. The moral sense was not to be distinguished from animal instinct but was instead derived historically from the social instincts and developed by natural selection. From this perspective, Darwin could claim a genuine identity of ethical foundations holding between humans and animals, with the precursors of human ethical behavior found in the behavior of other animals, particularly those with social organization. Natural selection then shaped these ethical instincts in ways that favored group survival over immediate individual benefit (ibid., 98). Human ethical behavior is therefore grounded in a natural property developed by natural selection, with the consequence that ethical actions can occur without moral calculus or rational deliberation.

When moral conflict occurs, this is generally attributed to a conflict of instincts, with the stronger of two conflicting instincts favored by natural selection insofar as it favors group benefit (ibid. 84). In human beings the “more enduring Social Instincts” thus come to override the less persistent “individual” instincts.

The adequacy of evolutionary ethical naturalism as a foundation for ethical realism proved to be a point of contention for Darwin’s contemporaries and successors following the publication of the Descent . For some moral philosophers, Darwin had simply reduced ethics to a property subject to the relativizing tendencies of natural selection (Farber 1994: chp. 5). It was, in the view of Darwin’s philosophical critics, to reduce ethics to biology and in doing so, to offer no way to distinguish ethical goods from survival advantages. Not even for some strong supporters of Darwinism, such as Thomas Huxley and Alfred Russel Wallace, was Darwin’s account adequate (ibid., chp. 4). Much of subsequent development of moral philosophy after Darwin would be grounded upon the canonical acceptance of the “is-ought” distinction, which emerged with new force from the critique of “evolutionary” ethical theory. This critique began with Thomas Huxley’s own break with Darwinian ethical theory in his Romanes Lecture, “Evolution and Ethics”of 1893 (Huxley 1893). This lecture, reflecting Huxley’s views eleven years after Darwin’s death, would play an important role in the Chinese reception of Darwinism (Huxley 1895; see above, section 3.1). This line of critique also received an influential academic expression in G. E. Moore’s (1873–1958) Principia Ethica —itself an attack on Spencer’s version of evolutionary ethics (Moore 1903). Debates over the adequacy of evolutionary ethics continue into the present (see the entries on biological altruism and morality and evolutionary biology ; see also, R. J. Richards 2015, 2009, 1999, 1987, Appendix 2; Charmetant 2013; Boniolo and DeAnna (eds.) 2006; Hauser 2006; Katz (ed.) 2000; Maienschein and Ruse (eds.) 1999).

4.4 Reception of the Descent

The international reception of the Descent of Man and Expression of the Emotions is a topic in need of the kind of detailed studies that surround the historical impact of the Origin. These works presented the reading public after 1871 with a more radical and controversial Darwin than had been associated with the author of the popular Journal of Researches or even the Origin itself, and his anthropological works created a watershed in the public reception of Darwin’s views (Radick 2013). The Descent finally made public Darwin’s more radical conclusions about human origins, and seemed to many of his readers, even those previously sympathetic to the Origin , to throw Darwin’s authority behind materialist and anti-religious forces. Public knowledge of Darwin’s own conclusions on human evolution before 1871 had rested on the one vague sentence on the issue in the Origin itself. The Descent made public his more radical conclusions. Even though the question of human evolution had already been dealt with in part by Thomas Huxley in his Man’s Place in Nature of 1863 (Huxley 1863), and by Charles Lyell in the same year in his Geological Evidences of the Antiquity of Man (Lyell 1863), followed by Alfred Russel Wallace’s articles in 1864 and 1870 (Wallace 1864 and online), these authors had either not dealt with the full range of questions presented by the inclusion of human beings in the evolutionary process, or they had emphasized the moral and mental discontinuity between humans and animals. Only Ernst Heinrich Haeckel had drawn out a more general reductive conception of humanity from evolutionary theory and he had not ventured into the specific issues of ethics, social organization, the origins of human races, and the relation of human mental properties to those of animals, all of which are dealt with in the Descent . Darwin’s treatise presented, as one commentator has put it, “a closer resemblance to Darwin’s early naturalistic vision than anything else he ever published” (Durant 1985, 294).

Darwin’s extension of his theory to a range of questions traditionally discussed within philosophy, theology, and social and political theory, has shaped the more general history of Darwinism since the 1870s. It set the agenda for much of the development of psychology of the late nineteenth century (R. J. Richards 1987). It also hardened the opposition of many religiously-based communities against evolutionary theory, although here again, distinctions must be made between different communities (Ellegård 1990, chp. 14). Such opposition was not simply based upon the denial of the literal scriptural account of the origins of humankind, an issue that played out differently within the main religious denominations (Haught 2013; Finnegan 2013; Swetlitz 2013; Artigas, Glick, & Martinez 2006; Moore 1979). The more fundamental opposition was due to the denial of distinctions, other than those of degree, between fundamental human properties and those of animals.

Furthermore, the apparent denial of some kind of divine guidance in the processes behind human evolution and the non-teleological character of Darwin’s final formulations of the natural selection theory in the fifth and sixth editions of the Origin , hardened this opposition. His adoption from Herbert Spencer of designator “survival of the fittest” as a synonym for “natural selection” in the fifth edition of 1869 added to this growing opposition. As a consequence, the favorable readings that many influential religious thinkers—John Henry Newman (1801–1890) is a good example—had given to the original Origin , disappeared. The rhetoric of the Descent , with its conclusion that “man is descended from a hairy quadruped, furnished with a tail and pointed ears” (Darwin 1871 [1981], 389), presented to the public a different Darwin than many had associated with the popular seagoing naturalist.

The new opposition to Darwin is reflected in the many hostile reviews of the Descent to appear in the periodical press (R. J. Richards 1987, 219–230). Particularly at issue were Darwin’s accounts of the origin of ethical principles and intelletual powers, including language, self-reflection, abstract thinking and religious belief as derivations from animal properties (Anon. 1871)

The profound revolution in thought that Darwin created, however, was eventually recognized even by his one-time harsh critics. The once leading British comparative anatomist Richard Owen (1804–1892), who had long been estranged from Darwin since his harsh review of the Origin in 1860, nonetheless could comment on the occasion of Darwin’s burial in Westminster Abbey in a letter to Horace Walpole:

The great value of Darwin’s series of works, summarizing all the evidence of Embryology, Paleontology, & Physiology experimentally applied in producing Varieties of Species, is exemplified in the general acceptance by Biologists of the Secondary Law, by Evolution, of the ‘Origin of Species’ […] In this respect Charles Darwin stands to Biology in the relation which Copernicus stood to Astronomy. […] [Copernicus] knew not how the planets revolved around the sun. To know that required the successive labours of a Galileo, a Kepler and finally a Newton […] Meanwhile our British Copernicus of Biology merits the honour and the gratitude of the Empire, which is manifest by a Statue in Westminster Abbey. (Richard Owen to Horace Walpole, 5 November, 1882, Royal College of Surgeons of England Archives, MS0025/1/5/4).

The subsequent history of the debates surrounding Darwin’s achievement forms a complex story that involves much of the history of life science, as well as ethical theory, psychology, philosophy, theology and social theory since 1870. For a general summary of recent scholarship see Ruse 2013a and articles from this encyclopedia listed below.

This article has intended to give a historical overview of the specific nature of Darwinian theory, and outline the ways in which it differed from the theories of predecessors in the nineteenth century (see the entry evolution before Darwin ). The eventual general consensus achieved by the middle of the twentieth century around the so-named “Synthetic” theory of evolution that would combine population genetics with a mathematical analysis of evolutionary change, has formed a successful research program for more than half a century (Smocovitis 1996; Mayr and Provine 1980; Provine 1971). This “synthesis” has been challenged in recent decades by the current movement known as evolutionary developmental theory, or “evo-devo”. This development represents in some important respects a return to presumably discarded traditions and lines of exploration of the nineteenth and early twentieth centuries which sought to link evolution with embryological development, and to a complex understanding of genetics, with re-examination of the effects of external conditions on inheritance (Gilbert 2015; Newman 2015; Laubichler and Maienschein 2007; Gissis and Jablonka 2011; Pigliucci and Müller 2010; Amundson 2005; Gilbert, Opitz and Raff 1996). Where these debates and revisions in evolutionary theory may lead in another fifty years is a matter of speculation (Gayon 2015 in Sloan, McKenny and Eggleson 2015).

More general philosophical issues associated with evolutionary theory—those surrounding natural teleology, ethics, the relation of evolutionary naturalism to the claims of religious traditions, the implications for the relation of human beings to the rest of the organic world—continue as issues of scholarly inquiry. The status of Darwin’s accounts of human mental powers and moral properties continue to be issues of philosophical debate. The adequacy of his reliance on sexual selection to explain sex and gender roles in human society form heated topics in some feminist scholarship. Such developments suggest that there are still substantial theoretical issues at stake that may alter the future understanding of evolutionary theory in important ways (Sloan, McKenny, & Eggleson [eds] 2015).

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  • Artigas, Mariano, Thomas F. Glick, and Rafael A. Martínez, 2006, Negotiating Darwin: The Vatican Confronts Evolution, 1877–1902 , Baltimore, MD: Johns Hopkins University Press.
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  • –––, 2013a, “Darwinism in Britain”, in Ruse 2013a: 218–225. doi:10.1017/CBO9781139026895.028
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  • –––, 1860, second edition [ Origin second edition available online ]
  • –––, 1861, third edition, [ Origin third edition available online ]
  • –––, 1862, first French edition, De l’origine des espèces , Clémence Royer (trans.), Paris: Guillaumin. [ Origin French first edition available online ]
  • –––, 1866, fourth edition, [ Origin fourth edition available online ]
  • –––, 1869, fifth edition, [ Origin fifth edition available online ]
  • –––, 1872, sixth edition, [ Origin sixth edition available online
  • –––, 1868, The Variation of Animals and Plants Under Domestication , two volumes, London: John Murray. First edition available online
  • –––, 1871 [1981], The Descent of Man, and Selection in Relation to Sex , two volumes, London: John Murray. Reprinted, ed John T. Bonner and Robert May, Princeton: Princeton University Press [ Descent 1871 available online ]
  • –––, 1872, Expression of the Emotions in Man and the Animals , London: John Murray. [ Expression available online ]
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  • Desmond, Adrian J., 1984, Archetypes and Ancestors: Palaeontology in Victorian London, 1850–1875 , Chicago: University of Chicago Press.
  • –––, and James R. Moore, 1991, Darwin , London: Michael Joseph.
  • –––, and James R. Moore, 2009, Darwin’s Sacred Cause: How a Hatred of Slavery Shaped Darwin’s Views on Human Evolution , Boston: Houghton, Mifflin, Harcourt.
  • Durant, John R., 1985, “The Ascent of Nature in Darwin’s Descent of Man ”, in Kohn 1985a: 283–306. doi:10.1515/9781400854714.283
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  • Elshakry, Marwa, 2013, Reading Darwin in Arabic, 1860–1950. Chicago: University of Chicago Press.
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adaptationism | altruism | altruism: biological | animal: cognition | animal: consciousness | biology: philosophy of | comparative cognition, methods in | creationism | Darwinism | evolution: concept before Darwin | evolution: cultural | fitness | genetics: ecological | life | morality: and evolutionary biology | moral sentimentalism | natural selection | natural selection: units and levels of | Newton, Isaac: philosophy | species | Spencer, Herbert | teleology: teleological notions in biology | Whewell, William

The author wishes to acknowledge the valuable comments on this version of the article by David Depew, Gregory Radick, M. J. S. Hodge, Alan Love, and Xiaoxing Jin. Additional comments were made on an earlier version by Michael Ruse, Robert J. Richards, Edward Zalta, M. Katherine Tillman, and the anonymous reviewers for the Stanford Encyclopedia of Philosophy. I am particularly indebted to Dr. Xiaoxing Jin for information contained in his substantial doctoral work and subsequent research on the reception of Darwinism into China. Responsibility for all interpretations is my own.

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Charles Darwin’s Evolutionary Theory

Introduction, problems/ challenge of evolution theory, works cited.

Evolution can be defined, in general terms, as any process of change over time (Evolution-Def. 2010, par.1). Evolution is a theory that was first developed by Charles Darwin, who is considered the father of evolution. Development of explanations as regards to the existence of man started to emerge long ago and they were in contrast with the biblical explanation of man’s origin. These explanations started to emerge as scientists were researching on rocks and they had found that man came to existence after vast periods when there was other creatures that existed before man (Bowler 1989, 2; 2003, 2). The evolutionists developed the idea that the possibility of these creatures were as a result of the laws of nature rather than miracles (divine). This, therefore, explained the human race as a mere species of animals, superior apes (Bowler 2003, 2). Furthermore this can be related to biological evolution, which refers to a theory that all living things are descendants (modified) of a common ancestor that existed long ago (Barton 2007, 7). It also portrays that man descended from apes, which also descended from more primitive creatures (Wells 2002, 4). This is the basis of Darwin’s theory that the human race was as a result of evolution. This theory aroused strong passions and to date there is still strong resistance for this theory. This was so much from a religious point of view who insists that the history of life can only be explained biblically, the book of Genesis (Bowler 2).

Some other philosophers and moralists have criticized scientific theories, of which Darwin’s evolution theory is, saying that there is no interpretation of nature that is completely free from the values of the people who articulate them (Bowler 2). This suggests that these theories are subjective and therefore, they cannot be fully relied upon to give a clear explanation about the origin of life. These contradicting views that affect the relationship of man’s existence and the natural world will therefore form the basis for our discussion. The essay, therefore, will discuss the problems of evolution theory as it was projected by Charles Darwin.

Darwin’s theory portrays that there is no difference that is fundamental between man and other higher mammals (primates) in their faculties of mind. He viewed that they share intellectual capacities that range from attentiveness to reasoning (Pope 189). Darwin in his opinion never saw any inherent conflict between evolution and human dignity. However, Darwin’s detractors felt otherwise regarding his opinion and theory on evolution. The challenge of Darwinian Theory is more from the theological point of view. The following is an analysis of the Darwinian challenge.

Firstly, Samuel Wilberforce, who was a bishop of Oxford, was the first to register worries about the origin of man as portrayed by Charles Darwin. He argued that that man’s power of articulate speech, reason, free will and responsibility were as a result of the fact that man was created, and by the image of God. This is contrary to Darwinian Theory which degrades the origin of man and the dignity of man from other animals (Pope 190). The Darwinian Theory is seen to lead to human worth degradation.

Secondly, William Jennings was of the conviction that common descent could only lead to social and personal immorality. He was arguing that if people came from monkeys, then we cannot expect people not to act like monkeys. The claims of having monkey ancestry, loosens the ethical restraints on the way we take life. He linked this with the way people could wage wars and the way that life could no longer be a big issue as regards to abortion. He continued to argue that if animals are perceived to only have instrumental worth, then humans too have instrumental worth only. This means that humans have no intrinsic moral worth, as they do not have rationality that is there because of the soul, therefore there is no rationality. Raising the level of animals closer to that of man, he continues, does not help at all. Escalating the values that animals have is accompanied to lowering the level and values of man (Pope 192).

Thirdly, John Paul II sees evolution to presuppose creation. His greatest reservation concerning evolution theory was from a moral concern. He argued that nature should not be interpreted in a way that should downgrade the dignity of human beings. He, therefore, disagrees that the soul of a human being can evolve from matter. The belief of creation of soul safeguards the dignity of human beings. It is only the body that can be noted in terms of evolution but not the soul, he argued. The spiritual soul can only be explained as a creation from God. He further argued that the fact that we are created in the image of God, we can be able to be in communion with God and with one another. Art, science and work are some of the avenues that human dignity is expressed (Pope 196).

Lastly we can site the fact that there are forces that operate in the universe that can only be related to the existence of a deity who is superior to man and animals in the universe. The forces and energies of nature can only be sensed, but their source is not revealed to us (Paley, James and John 231). Also the fact that humans are more privileged than animals in that they have five senses, more than that of the animals. It shows that there is a being that is superior whose personality we can not explain, and is responsible for the arrangement of the universe (Paley et al1860, 231). It is, therefore, concluded that the way nature works is as a result of intelligence and design from the creator (Paley et al 233). The views of nature have, therefore, deduced the suits in which our intellects universally enters into the idea of God (Paley et al 246), and this explains the existence of humans and why we have religions.

The evolution theory was developed by Charles Darwin and it tries to explain the source of life as a process of change overtime, and how humans are not any different from other forms of higher animal species. This has, however, been criticized as it is demeaning the dignity of the existence of humans and the fact that they were created and not evolved. The criticisms are more from a religious point of view that try to explain that the source of life can only be explained through the divine way, from the book of Genesis. The argument being that the soul can evolve from matter and have a sense of reasoning and moral responsibility, and thus there is a greater power that is beyond human imagination, and science, that is responsible for the way things are in the universe and which is considered as the source of life, not evolution from matter. Furthermore, the issue of a common ancestry would be demeaning and would therefore, be ruled out hence the Darwinian Theory is not the best way to explain the source of life, as it is a mere scientific approach which is prone to subjectivity.

Barton, Wells. Evolution. New York: CSHL Press, 2007. Print.

Bowler, Peter. Evolution: The History of an Idea. 2 nd Ed. California: California University Press, 1989. Print.

Bowler, Peter. Evolution: The History of an Idea. 3 rd Ed. California: California University Press, 2003. Print.

Paley, William, James Paxton and Ware, John. Natural Theology: or Evidences of the Existence and Attributes of the Deity, Collected from the Appearances of Nature. Michigan: Gould and Lincoln, 1860. Print.

Pope, Stephen. Human Evolution and Christian Ethics. Cambridge: Cambridge University Press, 2007. Print.

Wells, Jonathan. Icons of Evolution: Science or Myth?: why much of what we teach about evolution is wrong. Washington: Regnery Publishing, 2002. Print.

Wordiq.com. Evolution-definition. 2010. Web.

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Charles darwin.

Charles Darwin and his observations while aboard the HMS Beagle , changed the understanding of evolution on Earth.

Biology, Earth Science, Geography, Physical Geography

Historic photograph of Charles Darwin in profile.

Photograph by Chronical/Alamy Stock Photo

Historic photograph of Charles Darwin in profile.

Charles Darwin was born in 1809 in Shrewsbury, England. His father, a doctor, had high hopes that his son would earn a medical degree at Edinburgh University in Scotland, where he enrolled at the age of sixteen. It turned out that Darwin was more interested in natural history than medicine—it was said that the sight of blood made him sick to his stomach. While he continued his studies in theology at Cambridge, it was his focus on natural history that became his passion.

In 1831, Darwin embarked on a voyage aboard a ship of the British Royal Navy, the HMS Beagle, employed as a naturalist . The main purpose of the trip was to survey the coastline of South America and chart its harbors to make better maps of the region. The work that Darwin did was just an added bonus.

Darwin spent much of the trip on land collecting samples of plants, animals, rocks, and fossils . He explored regions in Brazil, Argentina, Chile, and remote islands such as the Galápagos. He packed all of his specimens into crates and sent them back to England aboard other vessels.

Upon his return to England in 1836, Darwin’s work continued. Studies of his samples and notes from the trip led to groundbreaking scientific discoveries. Fossils he collected were shared with paleontologists and geologists, leading to advances in the understanding of the processes that shape the Earth’s surface. Darwin’s analysis of the plants and animals he gathered led him to question how species form and change over time. This work convinced him of the insight that he is most famous for— natural selection . The theory of natural selection says that individuals of a species are more likely to survive in their environment and pass on their genes to the next generation when they inherit traits from their parents that are best suited for that specific environment. In this way, such traits become more widespread in the species and can lead eventually to the development of a new species .

In 1859, Darwin published his thoughts about evolution and natural selection in On the Origin of Species . It was as popular as it was controversial. The book convinced many people that species change over time—a lot of time—suggesting that the planet was much older than what was commonly believed at the time: six thousand years.

Charles Darwin died in 1882 at the age of seventy-three. He is buried in Westminster Abbey in London, England.

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How darwin’s theory of evolution evolved.

A new Smithsonian Book highlights firsthand accounts, diaries, letters and notebooks from aboard the HMS Beagle

Adrian Lister, Natural History Museum, London

Charles Darwin

The skulls and bones of extinct mammals were the crowning glory of Charles Darwin’s fossil collecting in South America, not only for him but for the eager recipients of the cargoes he sent home. They were the discoveries that made his name known beyond his immediate circle.

When the first consignment of fossil bones arrived at the Royal College of Surgeons in 1833, the puzzled curator, William Clift, recorded them as apparently “from a Mr Darwin at Rio de la Plata.” Only a few months later, however, after the specimens had been exhibited in Cambridge, Darwin's friend Frederick William Hope wrote to tell him that his “name was in every mouth.” Even more significantly, Darwin later credited the fossil mammals as one of the two main factors that led him to embrace the reality of evolution.

The most complete fossil of any mammal discovered by Darwin was an almost entire skeleton, later recognized as another new species of ground sloth by Richard Owen, a professor at the Royal College of Surgeons who described and named Darwin's fossils. It appears to have been found on the beach, partially embedded in loose sand, and Darwin concluded that the whole mass had fallen from the cliff.

The skeleton comprised the skull, vertebral column, ribs and limb bones down to the claws, “all nearly in their proper relative positions,” including even the kneecaps. This remarkable discovery was first noted by Darwin on September 1, 1833, and must have been made at some point during his second phase of collecting at Punta Alta, Argentina, the previous week.

Scelidotherium, Darwin's Fossils

Darwin quickly recognized the significance of finding an articulated skeleton; whereas odd bones might have been washed out of earlier deposits or fallen in from above, a complete skeleton embedded in sand demonstrated conclusively the contemporaneity of the living animal with the ancient deposit in which it was found. “Gran bestia all nonsense,” he exclaimed in his notebook, referring to a local legend, for it was perfectly clear that the remains were ancient and not those of a mysterious creature that still roamed the Pampas.

He wrote to his sister Caroline that he had discovered the skeleton of an animal “of which I do not think there exists at present on the globe any relation.” Later he wondered if it might represent the same species as the mandible whose four teeth he had previously illustrated, subsequently named Mylodon darwinii . On detailed comparison, however, Owen confirmed it as a different genus, smaller and with a more elongate skull, and named it Scelidotherium leptocephalum.

Another sloth species discovered by Darwin was found in November 1833 during his two-week excursion across present-day Uruguay. It was part of the back of a skull, later named Glossotherium by Owen. The find was made in the same stream, the Sarandi, where a larger, more complete skull of the celebrated mammal Toxodon had been discovered. It is not quite clear whether Darwin himself found the Glossotherium specimen at the stream, or obtained it from the finder together with the Toxodon , although the former seems more likely. At any event the specimen, which Darwin described as from “an animal rather larger than the horse,” was remarkable for its superb state of preservation; he wrote that it appeared “so fresh that it was difficult to believe [it had] lain buried for ages under ground.”

Glossotherium, Darwin's Fossils

Darwin's Fossils: The Collection That Shaped the Theory of Evolution

Richly illustrated with photos from the fossil collection and line drawings produced when Darwin was alive, Lister’s work is an essential acquisition for every library prizing quality books on evolution.

Not only was the appearance of the bone fresher than any of his other fossil finds, it preserved delicate parts that are usually broken away in ancient remains. This included the tympanic bone, one of the tiny ear bones. Its preservation in place in the skull lead Owen to praise “the care and attention devoted to his specimens by their gifted discoverer.”

Darwin wanted to know more. He held a piece of the bone in the flame of a spirit-lamp, finding that it not only burnt with a small flame, but “exhaled a very strong animal odour.” He sent a piece to Trenham Reeks at the Museum of Economic Geology in London, who had undertaken chemical analyses of several of his rock samples, asking what percentage of animal matter it contained. By this he meant organic material aside from bone mineral, and the answer was 7 percent. We would now recognize that around a quarter of the original protein content had been retained. The remarkable state of preservation of this skull, and its different appearance from others in Darwin’s collection, make it very likely to have fallen from a higher, later level in the river bank than the Toxodon and glyptodont remains found nearby.

Having only a fragment of skull at his disposal, Owen was characteristically cautious and identified it as an edentate without specifying to which group it belonged. A large attachment surface for the bone supporting the tongue, and a wide hole for the nerve supplying the latter, led him to reconstruct a very large tongue and to devise the name Glossotherium (tongue-beast). He later abandoned the name, considering the skull to belong the same species as the jaw that he had named Mylodon darwinii .

It is now recognized as being distinct, however, so Owen’s name has been reinstated and the species is known as Glossotherium robustum . Owen considered the animal might have been an insect-eater, breaking open termite nests like an anteater, but it is now known to have been herbivorous in its habits. Its wide muzzle suggests unselective bulk-feeding on grasses and low-growing herbs.

Glossotherium, Darwin's Fossils

In 2017, based on collagen protein extracted from Darwin's Glossotherium skull, a radiocarbon date of around 12,660 years ago was obtained. This is one of the latest known records of the genus, close to the time of its extinction. Glossotherium robustum had an estimated body weight of around 1.5 tonnes [1 ton U.S.].

In spite of this, a remarkable recent suggestion is that Glossotherium and/or Scelidotherium may have constructed large burrows to escape predation or unfavorable weather. Several lines of evidence support this idea. First, several large “fossil burrows” have been discovered, especially in the area around Buenos Aires, their diameter of 3 to 4.5 feet matches the body width of these species. Second, the forelimb bones of these animals appear modified for very powerful movements like digging. Third, claw marks have been found on the inside of some of the burrows, forming pairs of grooves that match closely the claws of the large second and third digits seen in these species. These sloths would be by far the largest animals known to burrow in this way—and one of the fossil burrows is more than 130 feet in length.

Darwin’s discovery on this journey of four genera of large ground sloths, Mylodon, Glossotherium, Scelidotherium and Megatherium was remarkable, and also serendipitous in that the area in which he was collecting happened to be the only region where all four could have been found together. Mylodon is distributed in the southern half of the continent, Glossotherium in the northern half, and Scelidotherium in the middle. The genus Megatherium is widespread, but M. americanum is known mainly from Argentina. Only in the Pampas region and La Plata basin do they overlap. The differing forms of their skulls, and teeth and limbs show how several species could have co-existed in the Late Pleistocene, using different food and habitat resources.

For Darwin, the relationship of the extinct giant sloths to the living species was one of the examples that led him to his “law of succession of types,” whereby there was an affinity between the past and present inhabitants of a particular region (in this case South America). This general pattern was one of the key factors that ultimately persuaded him of the reality of evolution.

Darwin’s Fossils: Discoveries that Shaped the Theory of Evolution by Adrian Lister, a research leader in the earth science department at the Natural History Museum, London, is published by Smithsonian Books.

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Understanding Evolution

Your one-stop source for information on evolution

The History of Evolutionary Thought

Natural selection: charles darwin & alfred russel wallace.

essay on charles darwin theory of evolution

Pre-Darwinian ideas about evolution

It was Darwin’s genius both to show how all this evidence favored the evolution of species from a common ancestor and to offer a plausible mechanism by which life might evolve. Lamarck and others had promoted evolutionary theories, but in order to explain just how life changed, they depended on speculation. Typically, they claimed that evolution was guided by some long-term trend. Lamarck, for example, thought that life strove over time to rise from simple single-celled forms to complex ones. Many German biologists conceived of life evolving according to predetermined rules, in the same way an embryo develops in the womb. But in the mid-1800s, Darwin and the British biologist Alfred Russel Wallace independently conceived of a natural, even observable, way for life to change: a process Darwin called  natural selection.

The pressure of population growth

Interestingly, Darwin and Wallace found their inspiration in economics. An English parson named  Thomas Malthus  published a book in 1797 called  Essay on the Principle of Population  in which he warned his fellow Englishmen that most policies designed to help the poor were doomed because of the relentless pressure of population growth. A nation could easily double its population in a few decades, leading to famine and misery for all.

When Darwin and Wallace read Malthus, it occurred to both of them that animals and plants should also be experiencing the same population pressure. It should take very little time for the world to be knee-deep in beetles or earthworms. But the world is not overrun with them, or any other species, because they cannot reproduce to their full potential. Many die before they become adults. They are vulnerable to droughts and cold winters and other environmental assaults. And their food supply, like that of a nation, is not infinite. Individuals must compete, albeit unconsciously, for what little food there is.

Selection of traits

carrier pigeon (bottom left) and the Brunner pouter (bottom right) were derived from the wild rock pigeon (top).

In this struggle for existence, survival and reproduction do not come down to pure chance. Darwin and Wallace both realized that if an animal has some trait that helps it to withstand the elements or to breed more successfully, it may leave more offspring behind than others. On average, the trait will become more common in the following generation, and the generation after that.

As Darwin wrestled with  natural selection  he spent a great deal of time with pigeon breeders, learning their methods. He found their work to be an analogy for evolution. A pigeon breeder selected individual birds to reproduce in order to produce a neck ruffle. Similarly, nature unconsciously “selects” individuals better suited to surviving their local conditions. Given enough time, Darwin and Wallace argued, natural selection might produce new types of body parts, from wings to eyes.

Darwin and Wallace develop similar theory

essay on charles darwin theory of evolution

Darwin began formulating his theory of natural selection in the late 1830s but he went on working quietly on it for twenty years. He wanted to amass a wealth of evidence before publicly presenting his idea. During those years he corresponded briefly with Wallace (right), who was exploring the wildlife of South America and Asia. Wallace supplied Darwin with birds for his studies and decided to seek Darwin’s help in publishing his own ideas on evolution. He sent Darwin his theory in 1858, which, to Darwin’s shock, nearly replicated Darwin’s own.

Origin of species book spine.

Charles Lyell  and Joseph Dalton Hooker arranged for both Darwin’s and Wallace’s theories to be presented to a meeting of the Linnaean Society in 1858. Darwin had been working on a major book on evolution and used that to develop  On the Origins of Species , which was published in 1859. Wallace, on the other hand, continued his travels and focused his study on the importance of biogeography.

The book was not only a best seller but also one of the most influential scientific books of all time. Yet it took time for its full argument to take hold. Within a few decades, most scientists accepted that evolution and the descent of species from common ancestors were real. But natural selection had a harder time finding acceptance. In the late 1800s many scientists who called themselves Darwinists actually preferred a Lamarckian explanation for the way life changed over time. It would take the discovery of  genes  and  mutations  in the twentieth century to make natural selection not just attractive as an explanation, but unavoidable.

  • More Details
  • Read more about  the process of natural selection  in Evolution 101.
  • Go right to the source and read Darwin's  On the Origin of Species by Means of Natural Selection .
  • Explore the  American Museum of Natural History's Darwin exhibit  to learn more about his life and how his ideas transformed our understanding of the living world.

Discrete Genes Are Inherited: Gregor Mendel

Early Evolution and Development: Ernst Haeckel

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Biology LibreTexts

12.2: Charles Darwin

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What you’ll learn to do: Describe the work of Charles Darwin in the Galapagos Islands, especially his discovery of natural selection in finch populations

Charles Robert Darwin, was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution. He established that all species of life have descended over time from common ancestors and, in a joint publication with Alfred Russel Wallace, introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding.

Darwin published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species , overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s, the scientific community and much of the general public had accepted evolution as a fact. However, many favored competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution. Darwin’s scientific discovery is the unifying theory of the life sciences, explaining the diversity of life.

In this outcome we’ll learn more about his work and how it helped develop the theory of evolution.

Learning Objectives

  • Outline the work of Charles Darwin as a naturalist aboard the HMS Beagle
  • Summarize the prior work and new evidence Darwin used to develop the idea of “descent with modification”
  • Describe how Darwin’s work developed to the theory of evolution

Darwin and Descent with Modification

Illustration shows four different species of finch from the Galápagos Islands. Beak shape ranges from broad and thick to narrow and thin.

In the mid-nineteenth century, the actual mechanism for evolution was independently conceived of and described by two naturalists: Charles Darwin and Alfred Russel Wallace. Importantly, each naturalist spent time exploring the natural world on expeditions to the tropics. From 1831 to 1836, Darwin traveled around the world on H.M.S. Beagle , including stops in South America, Australia, and the southern tip of Africa. Wallace traveled to Brazil to collect insects in the Amazon rainforest from 1848 to 1852 and to the Malay Archipelago from 1854 to 1862. Darwin’s journey, like Wallace’s later journeys to the Malay Archipelago, included stops at several island chains, the last being the Galápagos Islands west of Ecuador. On these islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences. For example, the ground finches inhabiting the Galápagos Islands comprised several species with a unique beak shape (Figure 1).

The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. He observed that these finches closely resembled another finch species on the mainland of South America. Darwin imagined that the island species might be species modified from one of the original mainland species. Upon further study, he realized that the varied beaks of each finch helped the birds acquire a specific type of food. For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey.

Wallace and Darwin both observed similar patterns in other organisms and they independently developed the same explanation for how and why such changes could take place. Darwin called this mechanism natural selection. Natural selection , also known as “survival of the fittest,” is the process by which organisms that are better adapted to their environment survive and pass those adaptations onto their offspring; this leads to evolutionary change.

For example, a population of giant tortoises found in the Galapagos Archipelago was observed by Darwin to have longer necks than those that lived on other islands with dry lowlands. These tortoises were “selected” because they could reach more leaves and access more food than those with short necks. In times of drought when fewer leaves would be available, those that could reach more leaves had a better chance to eat and survive than those that couldn’t reach the food source. Consequently, long-necked tortoises would be more likely to be reproductively successful and pass the long-necked trait to their offspring. Over time, only long-necked tortoises would be present in the population.

Natural selection, Darwin argued, was an inevitable outcome of three principles that operated in nature. First, most characteristics of organisms are inherited, or passed from parent to offspring. Although no one, including Darwin and Wallace, knew how this happened at the time, it was a common understanding. Second, more offspring are produced than are able to survive, so resources for survival and reproduction are limited. The capacity for reproduction in all organisms outstrips the availability of resources to support their numbers. Thus, there is competition for those resources in each generation. Both Darwin and Wallace’s understanding of this principle came from reading an essay by the economist Thomas Malthus who discussed this principle in relation to human populations. Third, offspring vary among each other in regard to their characteristics and those variations are inherited. Darwin and Wallace reasoned that offspring with inherited characteristics which allow them to best compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Because characteristics are inherited, these traits will be better represented in the next generation. This will lead to change in populations over generations in a process that Darwin called descent with modification. Ultimately, natural selection leads to greater adaptation of the population to its local environment; it is the only mechanism known for adaptive evolution. It is important to keep in mind that natural selection leads to adaptation to a specific environment, not all environments or even a different environment.

Papers by Darwin and Wallace (Figure 2) presenting the idea of natural selection were read together in 1858 before the Linnean Society in London. The following year Darwin’s book, On the Origin of Species , was published. His book outlined in considerable detail his arguments for gradual changes and adaptive survival by natural selection.

Paintings of Charles Darwin and Alfred Wallace are shown.

Demonstrations of evolution by natural selection are time consuming and difficult to obtain. One of the best examples has been demonstrated in the very birds that helped to inspire Darwin’s theory: the Galápagos finches. Peter and Rosemary Grant and their colleagues have studied Galápagos finch populations every year since 1976 and have provided important demonstrations of natural selection. The Grants found changes from one generation to the next in the distribution of beak shapes with the medium ground finch on the Galápagos island of Daphne Major. The birds have inherited variation in the bill shape with some birds having wide deep bills and others having thinner bills. During a period in which rainfall was higher than normal because of an El Niño, the large hard seeds that large-billed birds ate were reduced in number; however, there was an abundance of the small soft seeds which the small-billed birds ate. Therefore, survival and reproduction were much better in the following years for the small-billed birds. In the years following this El Niño, the Grants measured beak sizes in the population and found that the average bill size was smaller. Since bill size is an inherited trait, parents with smaller bills had more offspring and the size of bills had evolved to be smaller. As conditions improved in 1987 and larger seeds became more available, the trend toward smaller average bill size ceased.

While Charles Darwin is generally called “ the father of evolution ,” the basic idea for this concept was actually developed by both Darwin and Alfred Russel Wallace. Both scientists based their hypotheses on observations of diversity among natural populations. Darwin’s work in particular focused on animals of the Galapagos islands, especially finches. Over time, the idea that species changed from natural selection pressures through “descent with modification” gave rise to the idea of evolution. Data accumulated over time, for example the long study of the Galapagos finches by the Grant research team, has supported this idea and moved it into the realm of a supported theory of biology.

Darwin and the Theory of Evolution

Natural selection can only take place if there is variation , or differences, among individuals in a population. Importantly, these differences must have some genetic basis; otherwise, the selection will not lead to change in the next generation. This is critical because variation among individuals can be caused by non-genetic reasons such as an individual being taller because of better nutrition rather than different genes.

Genetic diversity in a population comes from two main mechanisms: mutation and sexual reproduction. Mutation, a change in DNA, is the ultimate source of new alleles, or new genetic variation in any population. The genetic changes caused by mutation can have one of three outcomes on the phenotype. A mutation affects the phenotype of the organism in a way that gives it reduced fitness—lower likelihood of survival or fewer offspring. A mutation may produce a phenotype with a beneficial effect on fitness. And, many mutations will also have no effect on the fitness of the phenotype; these are called neutral mutations. Mutations may also have a whole range of effect sizes on the fitness of the organism that expresses them in their phenotype, from a small effect to a great effect. Sexual reproduction also leads to genetic diversity: when two parents reproduce, unique combinations of alleles assemble to produce the unique genotypes and thus phenotypes in each of the offspring.

A heritable trait that helps the survival and reproduction of an organism in its present environment is called an adaptation . Scientists describe groups of organisms becoming adapted to their environment when a change in the range of genetic variation occurs over time that increases or maintains the “fit” of the population to its environment. The webbed feet of platypuses are an adaptation for swimming. The snow leopards’ thick fur is an adaptation for living in the cold. The cheetahs’ fast speed is an adaptation for catching prey.

Whether or not a trait is favorable depends on the environmental conditions at the time. The same traits are not always selected because environmental conditions can change. For example, consider a species of plant that grew in a moist climate and did not need to conserve water. Large leaves were selected because they allowed the plant to obtain more energy from the sun. Large leaves require more water to maintain than small leaves, and the moist environment provided favorable conditions to support large leaves. After thousands of years, the climate changed, and the area no longer had excess water. The direction of natural selection shifted so that plants with small leaves were selected because those populations were able to conserve water to survive the new environmental conditions.

The evolution of species has resulted in enormous variation in form and function. Sometimes, evolution gives rise to groups of organisms that become tremendously different from each other. When two species evolve in diverse directions from a common point, it is called divergent evolution. Such divergent evolution can be seen in the forms of the reproductive organs of flowering plants which share the same basic anatomies; however, they can look very different as a result of selection in different physical environments and adaptation to different kinds of pollinators (Figure 3).

Photo showing a Dense Blazing Star (Liatrus spicata) and a Purple Coneflower (Echinacea purpurea).

In other cases, similar phenotypes evolve independently in distantly related species. For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. However, the wings of bats and insects have evolved from very different original structures. This phenomenon is called convergent evolution , where similar traits evolve independently in species that do not share a recent common ancestry. The two species came to the same function, flying, but did so separately from each other.

These physical changes occur over enormous spans of time and help explain how evolution occurs. Natural selection acts on individual organisms, which in turn can shape an entire species. Although natural selection may work in a single generation on an individual, it can take thousands or even millions of years for the genotype of an entire species to evolve. It is over these large time spans that life on earth has changed and continues to change.

Natural selection, the driving force behind evolution, can only work if variation exists among organisms. Variation arises ultimately from genetic mutations. Diversity is further encouraged through sexual reproduction. As environments change, selective pressures shift and favor different adaptations. In this way, given thousands or millions of years, species evolve.

Check Your Understanding

Answer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does not count toward your grade in the class, and you can retake it an unlimited number of times.

Use this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.


Contributors and Attributions

  • Introduction to Charles Darwin. Authored by : Shelli Carter and Lumen Learning. Provided by : Lumen Learning. License : CC BY: Attribution
  • Modifcation of Charles Darwin. Provided by : Wikipedia. Located at : https://en.Wikipedia.org/wiki/Charles_Darwin . License : CC BY-SA: Attribution-ShareAlike
  • Biology. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/[email protected]
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Although there have been various theories of evolution throughout time, the most revolutionary theory for its era was developed by Charles Darwin, and described in his book On The Origin of Species.   This major work became the accepted science to explain evolution during its time and afterwards, although then as now, there continues to be controversy about this theory, since it contradicts the original ideas about Creationism and most recently, the notion of “intelligent design.” This paper shall discuss various aspects of Darwin’s theory of evolution, and its importance to our understanding of the development of all living things.

The concept of natural selection, or as some refer to it, “survival of the fittest,” has been the key element of Darwin’s theory that distinguished it from those that preceded it.  It is one of the basic elements of modern biology.  The idea of natural selection evolved in part because at that time, there was no legitimate explanation of heredity.  How did one explain the changes that occurred within various species over time?  Among the individuals of any group of organisms, there are many differences that do not have any relevance to the issue of survival, such as hair color.  However, some of the variations among people may increase the likelihood of survival of any particular person.  For example, a person with a history of heart disease is less likely to survive to old age than an individual with no such history.  Natural selection is a process by which certain characteristics of individuals increase their chances of reproduction and survival; if those characteristics are inherited from generation to generation, there will be a greater number of the healthier people over time that will survive and continue to reproduce.

As a result, if the reproductive advantage occurs over many generations, then those people will become a larger percentage of the population due to their exponential growth.  Darwin concluded that this produces in the environment the selection of people who survive, and over time, this causes gradual changes in the species.  The strongest prevail and survive, and the weakest die off.  Natural selection, as explained by Darwin, continues to be the main explanation for adaptive evolution.

Darwin’s theory of evolution involved several provable facts as well as certain inferences that contributed to the questioning of his theoretical basis.  Included among the factual aspects were: the knowledge that every species is fertile enough that if all offspring survive to reproduce, the population of that species would increase.  Despite subtle changes over time, the population would stay approximately the same in number.  However, because certain resources such as food and water occur in limited supply, and remain stable over time, while the population continues to explode, a struggle for survival develops.

According to natural selection theory, individuals are different from each other significantly, and many of these differences are passed down from generation to generation.  Finally, people who are less equipped to manage the environmental factors that affect their survival are less likely to reproduce or survive; those people who are more compatible with their environment are more likely to reproduce and to pass on these strong, adaptive traits to future offspring.

When it was introduced, Darwin’s theory was met with mixed reviews at best.  Primarily, the theory of evolution challenged the notion of Creationism, thereby creating a huge controversy and vehement condemnation of his “blasphemous” explanation of the universe.  As one writer put it, “Darwin’s theory is the culmination of a process which destroyed forever for us the oldest classification system in our history, the way in which our culture since the ancient Greeks has understood the world.”(Johnston, 1998.)  The previous ideas that came from ancient Greece combined Christianity with Plato’s theories regarding the goodness of God.  According to Plato, God’s perfection meant that all of his creations were perfect.  Therefore, any changes in beings which were seen as coming from the theory of evolution were considered to be a violation of the perfection of the highest power.  According to these theories, all possible forms of life were created in a hierarchy, which ranked the lowest, most primitive forms of life such as plants and animals, to the highest forms, human beings.  Even the range of human beings ranked from lowest to highest in status, from slaves to kings and queens and popes, and beyond that, to the angels, ultimately reaching God himself. (Johnston, 1998.)

Such vehement reactions against Darwinism and natural selection contrast with the theory’s acceptance by biologists, who considered it to be the basis for all aspects of the study of their discipline.  Natural selection helps to provide a basis for the classification of all living things, and an explanation of the variations and similarities that exist between such beings.  Replacing the divine elements of Creationist theories with Darwin’s theory of natural selection, while being extremely unsettling for people who were looking to God for explanations of how the universe began, allowed biologists and other scientific disciplines to move forward with pursuits that were demonstrably and scientifically sound.  Darwin did not publish his book casually; as a religious man himself, he worked on the book for a full decade before he had it published.  The suggestion of the theory of evolution is that God is not needed to create living organisms.  Darwin’s work freed up other scientists and philosophers to examine the creation of people, plants, and animals so that today, it is possible to find scientific advances that can save lives, prevent illnesses, and allow people to have more knowledge and freedom to decide personal issues such as reproductive freedoms.

Browne, Janet. Charles Darwin. Princeton, NJ: Princeton University Press, 1996.

Da Silva, W.. “Darwin at 200: the importance of dangerous ideas.” Cosmos.  December 2008: n. pag. Web. 20 Jun 2010. http://www.cosmosmagazine.com/features/print/2538/the-importance-dangerous-ideas

Johnston, Ian. “Some Non-Scientific observations on the importance of Darwin.” Malaspina-University. Nanaimo,BC: Malaspina-University College, 1998.  Web. 20 June 2010. http://records.viu.ca/~johnstoi/introser/darwin.htm

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  • Darwinian Essays
  • Open access
  • Published: 06 December 2008

Charles Darwin and Human Evolution

  • Ian Tattersall 1  

Evolution: Education and Outreach volume  2 ,  pages 28–34 ( 2009 ) Cite this article

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Along with his younger colleague Alfred Russel Wallace, Charles Darwin provided the initial theoretical underpinnings of human evolutionary science as it is practiced today. Clearly, nobody seeking to understand human origins, any more than any other student of the history of life, can ignore our debt to these two men. As a result, in this bicentennial year when Darwin’s influence in every field of biology is being celebrated, it seems reasonable to look back at his relationship to paleoanthropology, a field that was beginning to take form out of a more generalized antiquarian interest just as Darwin was publishing On the Origin of Species in 1859. Yet there is a problem. Charles Darwin was curiously unforthcoming on the subject of human evolution as viewed through the fossil record, to the point of being virtually silent. He was, of course, most famously reticent on the matter in On The Origin of Species , noting himself in 1871 that his only mention of human origins had been one single throwaway comment, in his concluding section:

“light will be thrown on the origin of man and his history” (Darwin 1859 , p. 488).

This has, of course, to rank among the most epic understatements ever. And of course, it begged the question, “what light?” But in the event, Darwin proved highly resistant to following up on this question. This is true even of his 1871 book The Descent of Man, and Selection in Relation to Sex in which Darwin finally forced himself to confront the implications of his theory for the origin of humankind, and the main title of which is in many ways something of a teaser.

There were undoubtedly multiple reasons for this neglect of the issue that was naturally enough in the back of everyone’s mind when reading The Origin , let alone The Descent of Man . First, and most famously, there was the intellectual and social milieu in which Darwin lived. During the second quarter of the nineteenth century, during which Darwin’s most formative experiences all occurred, England was at one level a place of intense political and social ferment. The Reform Act of 1832 had witnessed significant changes in the way Parliament was elected; the New Poor Law of 1834 had at least recognized problems in the system of poverty relief; and the founding of London University in 1826 had provided, at last, a secular alternative to the fusty Anglican Universities of Cambridge and Oxford. But despite all this, early Victorian England remained a strait-laced Anglican society whose upper classes, well remembering events in France not so long before, had little taste for radical ideas in any field.

In such an unreceptive milieu, the retiring Darwin had little relish for stirring things up with radical ideas on human emergence. He had originally planned to include mankind in the “Big Book” he was working on when spurred by Wallace into writing and publishing its “abstract” in the form of On the Origin of Species (Moore and Desmond, 2004 ). But despite having then made the conscious decision to avoid the vexatious and contentious issue of human evolution in On the Origin of Species , he still saw his book widely condemned as intellectual heresy, even as a recipe for the ruin of established society. As a result, while contemplating the publication of The Descent of Man a decade later, Darwin was still able to write to a colleague that:

“When I publish my book, I can see that I shall meet with universal disapprobation, if not execution” (in a letter to St. George Mivart, April 23, [probably] 1869).

As the least combative of men, Darwin dreaded the response he knew that any attempt to stake out a position on human origins would receive. And to be quite frank, given all his hesitations, it is not at all clear to me exactly why Darwin felt so strongly impelled to publish The Descent of Man or at least to have given it the provocative if not quite accurately descriptive title he did.

One possibility is merely that, during the 1860s, such luminaries as Alfred Russel Wallace, Ernst Haeckel, and Thomas Henry Huxley had all publicly tackled the matter of human origins and not invariably to Darwin’s satisfaction. As a result, Darwin may simply have felt it necessary to make his own statement on the matter, come hell or high water, in a decade that was already significantly more receptive to evolutionary notions than the 1850s had been. As to why it was so important to him to see it written, the Darwin historians James Moore and Adrian Desmond have pointed to an agenda that did not translate directly from Darwin’s stated desire simply:

“to see how far the general conclusions arrived at in my former works were applicable to man… all the more desirable as I had never applied these views to a species taken singly” (Darwin 1871 , ii, p. 2).

There was clearly more to it than that, and Moore and Desmond emphasize that Darwin came from a family of free-thinkers. He was the grandson both of the libertarian poet and physician Erasmus Darwin and of the Unitarian Josiah Wedgwood who had, in 1787, produced the famous “am I not a man and a brother?” cameo that became the emblem of the movement to abolish slavery. What is more, at a very impressionable age, Charles had attended the more or less secularist Edinburgh University in Scotland. There he had studied under the anatomist Robert Grant who quoted Lamarck with approval; and there also he was taught taxidermy by John Edmondston, a freed slave from British Guiana for whom he developed very considerable respect.

From the very beginning, then, Darwin abhorred slavery; and he was already a convinced abolitionist by the time he boarded the Beagle in 1831 for his formative round-the-world voyage. His subsequent experiences in Brazil, where he witnessed hideous cruelties being inflicted on slaves, and in Argentina, where he saw the pampas Indians being slaughtered to make way for Spanish ranchers, only confirmed him in his egalitarian beliefs. This concern linked in with Darwin’s strong views on the unity of mankind. In the early and middle nineteenth century, this was a very hot topic in the English-speaking world, even “the question of the day,” as the blurb to a book by the Presbyterian abolitionist Thomas Smyth ( 1850 ) put it.

The precise question at issue was of course whether the races of mankind had been separately created (or even, after The Origin of Species was published, descended from different species of apes), as the proslavery polygenists proposed; or whether they were simply varieties of one single species, as proclaimed by the antislavery monogenists.

In this matter, there was little hope that science could ever be disentangled from politics; and it was this, above anything else, it seems, that had dissuaded Darwin from including humans in On the Origin of Species . By 1871, however, the world had changed enough to allow Darwin to contemplate entering the fray; and there is substantial reason for viewing The Descent of Man as Darwin’s contribution on the monogenist side to the monogenism versus polygenism debate—although Moore and Desmond ( 2004 ) make a strong argument that, in the end, it became at least as important to Darwin as a showcase for his notion of sexual selection.

Indeed, these two aspects could hardly be separated, since sexual selection—in other words, mate choice—was Darwin’s chosen mechanism to explain:

“the divergence of each race from the other races, and all from a common stock” (Darwin 1871 , ii, p. 371).

And most of the book is, in true Darwinian style, taken up with hugely detailed documentation of sexual selection among organisms, in support of the proposition that humankind was simply yet another product of Nature, albeit with many of its peculiar features governed by mate choice rather than by adaptiveness.

Still, Darwin had chosen to title his book The Descent of Man . And “descent” was a word that he had long used as equivalent to “ancestry.”

Given which, it seems at the least a bit odd that in the entire two volumes of the first edition of the work only passing consideration at best is given to those fossils that might have given a historical embodiment to the notion of human emergence. Even when Darwin wrote the Origin in 1858–1859, a handful of “antediluvian” human fossils was already known. The most famous of these was the skullcap and associated bones discovered in 1856 in the “Little Feldhofer Grotto,” a limestone cave in the Neander Valley, near Dusseldorf in Germany. This fossil, associated with the bones of mammal species now extinct, was destined in 1863 to become the type specimen of Homo neanderthalensis , now known to be an extinct cousin of our own species, Homo sapiens . But it was not published until 1858, barely a year before the Origin appeared; and even then, it was described in German, in a rather obscure local scientific journal, making it highly unlikely that the Neanderthal fossil came to Darwin’s attention before Hermann Schaaffhausen’s work on it was translated into English by the London anatomist George Busk in 1861. Still, this was an entire decade before The Descent of Man first appeared, which makes it a little odd that the detail-obsessed Darwin made virtually no reference to the Feldhofer fossil in a book which one might have expected to find it at front and center or at least introduced as a phenomenon to be explained. Only in passing did he mention it at all.

The neglect of the Neanderthal fossil is all the more remarkable in light of the fact that, in 1863, George Busk had already described another individual, of similarly distinctive appearance, from the British possession of Gibraltar. Taken together, these two specimens had demonstrated pretty conclusively by the mid-1860s that here was not simply a pathological form of Homo sapiens , as many influential biologists had claimed, but at the very least a highly distinctive human “variety” that needed explanation of some kind. In sharp contrast to any modern human fossils then known from anywhere in the world, the Neanderthal skull was very long and low. What’s more, it terminated in front in prominent brow ridges that arced individually above each eye and at the rear in a curious bulge that became known as a “chignon” or “bun.” On the other side of the balance, this skull had evidently contained a brain that was equal in size to the brain that resided in the heads of modern people. Either way, it was obviously an important fossil.

Yet the only reference that the astonishingly erudite Darwin made to this fossil, in almost 800 pages of dense text, was in the context of a throwaway admission that:

“some skulls of very high antiquity, such as the famous one of Neanderthal, are well developed and capacious.” (Darwin 1871 , i, p. 140).

It is hard not to conclude that, in limiting his reference to the Feldhofer in this way, Darwin was grasping at the politically congenial notion that the Neanderthaler, ancient as it was, was simply a bizarre kind of modern human. For perhaps more remarkably yet, nowhere in The Descent of Man did Darwin directly confront the idea that the human species might even in principle have possessed extinct relatives—despite the fact that the entire Origin of Species is suffused with the notion that having extinct relatives must be a general property of all living forms.

In his introduction to The Descent , Darwin partially excused himself for only passing reference to human antiquity by deferring to the work of Jacques Boucher de Perthes, Charles Lyell, his protégé Sir John Lubbock, and others. But there was very likely another key to Darwin’s reluctance to embroil himself too closely with the actual tangible evidence for human ancientness and ancestry. For the 1860s, the years leading up to the publication of the Decent of Man , were a period of rampant fraud and fakery in the antiquities business—and a business it certainly was. By the time Darwin published the Descent , it was widely accepted that, at the very least, the human past far antedated Biblical accounts. And an energetic search was on for evidence of that ancient past, with wealthy dilettantes pouring money into excavations all across Europe. Today, we honor the French antiquarian and customs-collector, Boucher de Perthes, as the first man to recognize the Ice Age stone handaxes found in the terraces of the Somme River as the products of truly ancient humans. But in the 1840s and 1850s, Boucher de Perthes was widely ridiculed as the gullible victim of hoaxers; and indeed, it is true that he was entirely undiscriminating in what he was prepared to consider ancient. Many of his prize artifacts turned out later to have been knapped by his quarrymen, who were only too happy to con their employer out of a few francs. Indeed, there is a charming story of a lady who asked a local peasant what he was doing chipping away at a piece of flint and was told: “Why, I am making Celtic handaxes for Monsieur Boucher de Perthes.” “Celtic” was then the current term for anything prehistoric.

Of course, Boucher de Perthes was not alone. For profitable deception of the gentry, by clever tricksters from the underclasses, was a rather sporting component of class warfare all across Europe in the mid—nineteenth century. But Boucher de Perthes had, in particular, been embroiled in a famous hoax involving a supposedly antediluvian human fossil (Trinkaus and Shipman 1993 ). In early 1863, he offered a reward of 200 francs to any workman who could find the remains of the maker of his ancient stone tools. And on March 28 of that year, a supposedly ancient human jawbone duly showed up, along with handaxes, at a site called Moulin-Quignon. A scandal almost immediately blew up over the authenticity of this object and the stone tools supposedly associated with it; and eventually, an international commission was convened to settle the matter. This committee of savants consisted of various French luminaries, plus several English scientists including George Busk. Eventually, the commission exonerated Boucher de Perthes himself as a fraudster, but remained deadlocked over the authenticity of the fossil and tools. The French intelligentsia mostly accepted them for political reasons, while the English remained opposed. And the whole affair added up to the sort of unseemly squabble that Darwin most detested and always did his best to avoid.

What’s more, there were similar and equally embarrassing scandals closer to home. In England, the so-called “Prince of Counterfeiters” was one Edward Simpson, alias “Flint Jack” (Milner 2008 ). During several years of assisting a local physician who dug for antiquities in his spare time, Flint Jack taught himself the art of stoneworking. Soon, this gifted flintknapper was producing supposedly Stone Age tools that would fool even the most expert eye. And he sold his forgeries to collectors and museums all over the country. Finally, he brazenly peddled them as his own work, before the sheer quantity of real Stone Age artifacts coming on to the market put him out of business. There can be little doubt that Darwin found all this fraud and scandal in the antiquarian marketplace very distasteful. And it must surely have been at least one more contributory factor in his reluctance to dabble in the human fossil record.

Still, it is nonetheless necessary to ask why Darwin gave even the idea of an actual fossil ancestry for humans such a wide berth in his great work on human descent. In this connection, it is quite possibly enough to conclude with Moore and Desmond ( 2004 ) that Darwin considered it simply too provocative, both politically and socially, to tie human ancestry in with any tangible evidence. For it is well known that even the contemplation of doing so caused this complex and delicate man extreme physical and mental distress; and it certainly seems plausible that Darwin felt that limiting himself to the comparative method, contrasting humans with apes, and merely conjecturing about possible transitional forms, was somehow the safest route to take. After all, those speculative intermediates remained hypothetical, unenshrined in any material object that his opponents might take exception to.

However, it is possible that another contributing factor may well have been Darwin’s rather suspicious attitude toward the fossil record itself—which in the nature of things is the only direct archive we have of the origins and evolution of the human family or any other. Of course, by its very nature, the fossil record is and always will be incomplete. And in Darwin’s time, 150 years ago, it was vastly more incomplete than it is now, and conspicuously lacked many of the intermediate forms predicted by Darwin’s theory. But while under such circumstances it is completely understandable that Darwin would not have wished to embrace the fossil record as a key element bolstering his notion, he seems to have deliberately shied away from it. Thus, under the rubric of “Objections to the Theory,” he devoted an entire chapter in the Origin of Species to the “Imperfection of the Geological Record,” enumerating reason after reason not only why this record was not adequate, but why it could not be adequate.

“Geology assuredly does not reveal any such finely graduated chain [as evolution requires]; and this, perhaps is the gravest objection which can be urged against my theory. The explanation lies, as I believe, in the extreme imperfection of the geological record.” (Darwin 1859 , p. 280).

Even in the remarkably brief chapter of the Origin in which he recruited the fossil record to his cause, Darwin was dubious:

“[numerous causes] must have tended to make the fossil record extremely imperfect, and will to a large extent explain why we do not find interminable varieties, connecting together all the extinct and existing forms of life by the finest graduated steps.” (Darwin 1859 , p. 342).

Darwin’s general wariness of the fossil record may seem a bit odd in a person who not only considered himself first and foremost a geologist, but whose nascent ideas about the history of life had been so clearly nourished by the fossils he had encountered during his voyage on the Beagle . For Darwin was always ready to acknowledge what a seminal event his discovery during the Beagle voyage of the amazing South American fossil glyptodonts had been for him. The glyptodonts are large extinct armored xenarthrans, relatives of today’s armadillos and sloths, which are found quite abundantly in Ice Age geological deposits of southern South America. And finding these extinct beasts in the very same place as surviving members of their family—something that implied the replacement of faunas by related ones—was a revelation to Darwin:

“[I was] deeply impressed by discovering in the Pampean formation great fossil animals covered with armour like that of the existing armadillos” (C. Darwin in F. Darwin 1950 , p. 52).

Indeed, as Eldredge ( 2005 ) points out, Darwin’s encounter with the glyptodonts constituted one of the three key observations that first led him toward the explicit realization that species were not immutable.

This realization was a truly formative one because, for Darwin, the adoption of the corollary belief in the “transmutation of species” was fundamental to everything that was to follow, and it was emotionally as well as intellectually a difficult transition for him to make. In an 1844 letter to Joseph Hooker, Darwin famously described how admitting his new belief was “like confessing a murder,” and it was as formidable a psychological hurdle as he faced in his entire career. Still, although his geological observations had made Darwin acutely aware of the transitory nature of everything he saw around him, he clearly felt very acutely the inadequacies of the fossil record for determining specific events. And although the notion that fossil “missing links” were out there to be discovered was soon to become a governing principle of the quest for human origins, Darwin himself seems to have remained rather dubious that such links would ever be found.

Of course, the whole notion of links, missing or otherwise, came from the medieval concept of the Great Chain of Being with which Darwin was philosophically in contention—indeed, in a marginal note in one of the Notebooks , he specifically warned himself against ever using the terms “higher” or “lower” in relation to living beings. But the Great Chain of Being, the idea that all living things were ranged in graded series, was nonetheless part of the ethos that suffused English society, and it was a notion from which Darwin found it difficult to disengage himself entirely. For it was not only a religious concept with a succession of forms leading from the most lowly pond scum, through mankind, the highest Earthly form, on up to the Angels and God above. It had political and social dimensions as well. On one hand, the Great Chain ranked the races of mankind from “lower” to “higher;” and on the other, within English society, it carried through the social order with peasants and servants at the bottom, then tradesmen and the gentry, then the nobility, and on up to royalty at the top who served to link earthly and heavenly existences. Correspondingly, the designations of “lower” and “higher,” stemming directly from the Great Chain notion, proved irresistible to zoologists: lemurs, for example, were and still are “lower” primates, while apes and humans are “higher primates.”

It is well-established that, long before he published On the Origin of Species , Darwin was fully aware that his theory firmly placed our species Homo sapiens as simply another product of the evolutionary process, among literally millions of others. So, while the effective absence of a hominid fossil record before he published the Origin may have meant that Darwin could not have made extensive reference to it there if he had wanted to, we still need to ask if there are reasons beyond the admittedly powerful sociopolitical ones why he more or less ignored it in the post-Neanderthal times of The Descent of Man . One reason for such neglect is, of course, the very specific monogenist agenda that Darwin was pursuing in that work. But another reason may be that his colleague Thomas Henry Huxley, who is often, if misleadingly, referred to as “Darwin’s Bulldog,” had already tackled the matter head-on in his 1863 book of essays, Evidence as to Man’s Place in Nature .

The last chapter in Huxley’s book was explicitly titled On Some Fossil Remains of Man , and it dealt exclusively with the best-preserved and best-documented fossil humans known at the time: the Neanderthal skullcap already mentioned, and two partial crania from Engis, in Belgium, that had been published by Philippe-Charles Schmerling in the early 1830s. By the time Huxley wrote, the Engis fossils had been certified as contemporaneous with the extinct Ice Age wooly mammoth and wooly rhinoceros by no less an authority than Darwin’s close colleague the geologist Charles Lyell, who had also pronounced the Neanderthaler to be of “great but uncertain antiquity.” We now know that one of the Engis crania, a juvenile braincase, had belonged to a Neanderthal. However, since many of the osteological differences between Homo neanderthalensis and Homo sapiens only emerge later in development, it is fully understandable that Huxley (like everyone else at the time) did not recognize it as such. And in any event, Huxley basically ignored it. The other Engis cranium was adult, and it was on a plaster cast of this specimen that Huxley based his analysis. The Engis adult clearly is a Homo sapiens and it is now known to represent a later burial into the Neanderthal deposits at the site—which means it is younger than those deposits.

Huxley’s ignorance of this fact may not in fact have mattered much, in light of his rather perfunctory and dismissive analysis of the adult Engis specimen. He recognized this cranium as that of a fully modern person, concluding that it:

“has belonged to a person of limited intellectual faculties, and we conclude thence that it belonged to a man of a low degree of civilization” (Huxley 1863 , pp. 114–115).

He then continued to the Neanderthal skull, an altogether more interesting specimen, and to which he devoted much greater space. Initially, he quoted extensively from Schaaffhausen who had declared that the bones:

“exceed all the rest in those peculiarities of conformation which lead to the conclusion of their belonging to a barbarous and savage race.” (Schaaffhausen 1861 , translated by Busk).

Huxley finally proceeded to a detailed examination of the Neanderthal skullcap, again based on a plaster cast. He was amazed by the differences between the cranial contours of the Neanderthal and Engis crania, but he noted that:

“…the posterior cerebral lobes [of the Neanderthaler] must have projected considerably beyond the cerebellum, and… [this] constitutes one among several points of similarity between [it] and certain Australian skulls” (Huxley 1863 , p. 134).

As Schwartz ( 2006 ) has pointed out, the comparison with “certain Australian skulls” comes straight out of the Great Chain of Being. For in nineteenth-century European scientific mythology, the Australian aborigines belonged, along with the South African Bushmen, to the “lowest” of races. Having established this philosophical baseline, Huxley proceeded to a long dissertation about variation in human skulls, eventually concluding that the key to comparison among them was provided by the basicranial axis, a line between certain points on the internal base of the skull:

“I have arrived at the conviction that no comparison of crania is worth very much, that is not founded upon the establishment of a relatively fixed base line… the basicranial axis.” (Huxley 1863 , pp. 138–40).

He then showed, to his own satisfaction, that relative to this axis, the basicranium became shorter “in ascending from the lower animals up to man” and that this trend was continued up from the “lower” human races to the “higher” ones. In which case:

“Now comes the important question, can we discern, between the lowest and highest forms of the human cranium, anything answering, in however slight a degree, to this revolution of the side and roof bones of the skull upon the basicranial axis observed upon so great a scale in the mammalian series? Numerous observations lead me to believe that we must answer this question in the affirmative.” (Huxley 1863 , pp 140–142).

One might object at this point that the basicranial axis had no relevance whatever to the Feldhofer Neanderthal, a specimen that totally lacked a skull base. The important thing here, though, was that Huxley had managed to establish a graded series. And by superimposing the profile of the Neanderthaler onto an Australian skull, he contrived to convince himself that:

“A small additional amount of flattening, and lengthening, with a corresponding increase of the supraciliary ridge, would convert the Australian brain case into a form identical with the aberrant [Neanderthal] fossil.” (Huxley 1863 , p. 146).

Nonetheless, whereas:

“[The Engis skull] is… a fair average human skull, which might have belonged to a philosopher, or might have contained the thoughtless brains of a savage… The case of the Neanderthal skull is very different. Under whatever aspect… we meet with ape-like characters, stamping it as the most pithecoid of human crania yet discovered” (Huxley 1863 , p. 147).

Yet, at the same time, the Neanderthal skullcap had held a large brain—larger, indeed, than the modern average. Furthermore, although the preserved bones of the individual’s skeleton were robustly built, Huxley felt that such stoutness was to be “expected in savages” (Huxley 1863 , p. 148). As a result, he concluded that:

“In no sense… can the Neanderthal bones be regarded as the remains of a human being intermediate between men and apes. At most, they demonstrate the existence of a man… somewhat toward the pithecoid type… the Neanderthal cranium… forms… the extreme term of a series leading gradually from it to the highest and best developed of human crania” (Huxley 1863 , p. 149).

By this intellectual sleight of hand, Huxley dismissed the Neanderthal find as a mere savage Homo sapiens , essentially robbing the slender human fossil record then known of any potential human precursor. Instead, in a move that was as radical in its own way as the alternative would have been, Huxley pushed the antiquity of the species Homo sapiens back into the remotest past and was moved to ask:

“Where, then, must we look for primaeval Man? Was the oldest Homo sapiens pliocene or miocene, or yet more ancient? In still older strata do the fossilized bones of an ape more anthropoid, or a Man more pithecoid, than any yet known await the researches of some unborn palaeontologist?” (Huxley 1863 , p. 150).

Taken overall, this rather startling conclusion was not just a major shift away from the demonstrable morphology of the Neanderthal specimen—which in the same year had been branded a distinct species, Homo neanderthalensis , by the Dublin anatomist William King. It was also a considerable reversal of perspective for one who had been a convinced saltationist. After all, when reviewing On the Origin of Species , Huxley had been moved to observe that:

“Mr Darwin’s position might, we think, have been even stronger than it is if he had not embarrassed himself with the aphorism ‘ natura non facit saltum ,’ which turns up so often in his pages. We believe… that Nature does make jumps now and again, and a recognition of that fact is of no small importance in disposing of many minor objections to the doctrine of transmutation” (Huxley 1860 , p. 77).

Famously combative though Huxley was, with none of Darwin’s reluctance to hash out in public the implications of evolution for human origins, he too had thus caved when it came to the contemplation of the human fossil record.

What Huxley’s motives may have been in this, it is hard to judge. But I am pretty sure that Jeffrey Schwartz ( 2006 ) was correct to suggest that, if Huxley had been writing in Man’s Place in Nature about any other mammal than a hominid, he would have reached a very different conclusion. Almost certainly, he would have discerned one of Nature’s jumps between the Neanderthaler and the avowedly “higher” type from Engis. As it was, however, Huxley elected to reject the idea that the Feldhofer Neanderthal specimen had belonged to “a human being intermediate between men and apes” in favor of viewing it as a member of Homo sapiens , via an extension into the past of the widely assumed “racial hierarchy” that expressed itself in terms not only of morphology, but of technology, society, and presumed intelligence. In a very real sense, then, it is to Huxley that we can trace the exceptionalism that has dogged paleoanthropology ever since.

Historically, however, the significance of Huxley’s contribution goes beyond this. For by employing anti-Darwinian reasoning in support of the conclusion that the Feldhofer fossil was merely a brutish Homo sapiens , Huxley had provided Darwin with just the excuse he needed not to broach the fossil evidence seriously in The Descent of Man . Darwin could brush the crucial Neanderthal fossil off in passing because Huxley, in however non-Darwinian a spirit and however much in contradiction of his own principles, had given him license to.

There were, then, many reasons why Darwin should have been disposed in The Descent of Man to shrink from any substantive discussion of whether extinct human relatives might actually be represented in fossil form. The fossil and antiquarian records were awash with fakes; any discussion of human ancestry was rife with social and political pitfalls; and anyway, by his own close colleague’s testimony, the record contained nothing that could have any relevance to ancient and now-extinct human precursors. Add to that Darwin’s innate suspicion of the distorting effects of incompleteness in the fossil record, and he may have felt that a large degree of discretion on the matter was mandatory.

None of this means, of course, that The Descent of Man has not exerted an immense influence on the sciences of human origins over the last century and a half. Just as it is easy for English speakers to forget how much they owe to William Shakespeare for the language they use daily, we tend to lose sight of the fact that much received wisdom in paleoanthropology has come down to us direct from Darwin. Darwin it was who proposed a mechanism for the structural continuity of human beings with the rest of the living world and who gave a detailed argument for human descent from an “ape-like progenitor” (1871, i, p. 59). It was Darwin who documented beyond doubt, in The Descent of Man , that all living humans belong to a unitary species with a single origin—which we now know, on the basis of evidence of which Darwin could never have dreamed, to have been around 200,000 years ago.

He also had the inspired hunch that our species originated in the continent of Africa—and again, this guess has been amply substantiated by later science. Darwin’s perceptions on the behaviors of other primates and how they relate to the way humans behave were remarkably astute, particularly given the highly anecdotal nature of what was then known.

And, for better or for worse, a single comment in The Origin is proclaimed as founding Scripture by practitioners of today’s evolutionary psychology industry:

“In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history” (Darwin, 1859 , p. 488; emphasis added).

Virtually every section in the first part of the Descent of Man foreshadows an area of anthropology or biology that has independently flowered since; and in this way, Darwin wrote much of the agenda that was to be followed by paleoanthropology and primatology over the next century and a half.

I just wish I knew what he really thought about the Neanderthal fossil!

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I would like to thank Niles Eldredge for inviting me to contribute this piece and Richard Milner for the valuable discussion.

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essay on charles darwin theory of evolution

Darwin’s Theory of Human Evolution Essay

Darwin’s evidence to theory of human evolution.

Darwin presents several arguments to support his proposition that man originated from some form of lowly species. To begin with, he asserts that the embryonic development between man and other animals is similar. In other words, the growth cycle of man and other lowly animals or organism demonstrates a lot of distinct similarities that have never been disputed.

For example, conception is the first process of bringing forth life in both man and other animals. Second, the stages of embryonic development are similar in both cases because the embryo takes a particular period before it can transform into a new form of life or creation. Darwin notes that the conception period might be the only difference between man and other living organisms.

There is also a close similarity between man and other animals in terms of geographic distribution. Both of them have been spatially distributed in such a way that they can depend and co-exist with each other. The spatial distribution of man and other animals is also largely dependent on the availability of resources required for sustainable growth.

The evolutionist also stresses the point that even though man has been classified in form other races, it is similar to the case of other animals. Perhaps, the only difference is the wording pattern because animals are grouped into species while human beings are categorized in various races. Also, man retains the same rudiments as other lower animals because he descended from a lowly organized form. Darwin has used these pieces of evidence to support his theory of evolution.

Question of the Relationship Between Religion and Science

Although Darwin seems to refute the religious claim on the origin of man, it is apparent that both religion and science share a common hypothesis that man has a distinct origin. Nonetheless, the evidence provided above by Charles Darwin contrast the religious belief that man was created by the Supreme Being called God. Science does not recognize the presence of God as referred by Christians and other religions.

Also, it is prudent to underscore the fact that science relies on evidence that can be proven while religion revolves around various abstract belief systems with no evidence at all. This explains why the evidence provided by science on the evolution of man cannot be accommodated by religion. Therefore, religion and science will continue to offer opposite thoughts and perspectives due to the parallels that have been drawn between evidence and belief systems (Lualdi 182).

Darwin Voice the Concern for Realism and Concrete Facts

Darwin readily mentions that several critics will judge his theory of evolution on the origin of the species without giving key attention to the concrete facts and realism presented by the same theory. He appears to be quite aware that the theory may elicit a long debate afterward. Indeed, the evolution theory was not received warmly from all quarters because Darwin was sharply criticized by religious adherents and other scientists.

The evolution theorist emphasizes that he has offered adequate scientific knowledge on the origin of man because he is aware that the theory is bound to be the core subject of discussion for a long time. Darwin is also concerned that hopes and fears can hardly reveal the pertinent facts on the origin of man. He adds that truth based on scientific evidence should be the main guideline on all arguments presented from different viewpoints.

Works Cited

Lualdi, K. Sources of the Making of the West: Peoples and Cultures. Volume II: Since 1500 . Boston: Bedford/St. Martin’s, 2012. Print.

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What is Darwin's Theory of Evolution?

Charles Darwin's Theory of Evolution is one of the most solid theories in science. But what exactly is it?

The hominin wall at the Natural History Museum of Utah in Salt Lake City.

  • Natural selection
  • Origin of whales
  • Rival theories of evolution
  • Modern evolutionary synthesis
  • Evidence for evolution
  • Is evolution controversial?

Additional resources

The Theory of Evolution by natural selection was first formulated in Charles Darwin's book " On the Origin of Species " published in 1859. In his book, Darwin describes how organisms evolve over generations through the inheritance of physical or behavioral traits, as National Geographic explains. The theory starts with the premise that within a population, there is variation in traits, such as beak shape in one of the Galapagos finches Darwin studied. 

According to the theory, individuals with traits that enable them to adapt to their environments will help them survive and have more offspring, which will inherit those traits. Individuals with less adaptive traits will less frequently survive to pass them on. Over time, the traits that enable species to survive and reproduce will become more frequent in the population and the population will change, or evolve, according to BioMed Central . Through natural selection, Darwin suggested, genetically diverse species could arise from a common ancestor . 

Darwin did not know the mechanism by which traits were passed on, according to National Geographic. He did not know about genetics , the mechanism by which genes encode for certain traits and those traits are passed from one generation to the next. He also did not know about genetic mutation, which is the source of natural variation. But future research by geneticists provided the mechanism and additional evidence for evolution by natural selection

What is natural selection?

Darwin chose the term "natural selection" to be in contrast with "artificial selection," in which animal breeders select for particular traits that they deem desirable. In natural selection, it's the natural environment, rather than a human being, that does the selecting.

Put simply, the theory of evolution by means of natural selection can be described as "descent with modification," said Briana Pobiner , an anthropologist and educator at the Smithsonian National Museum of Natural History in Washington, D.C., who specializes in the study of human origins. The theory is sometimes described as "survival of the fittest," but that characterization can be misleading, Pobiner said. Here, "fitness" refers not to an organism's strength or athleticism but rather its ability to survive and reproduce.

Natural selection can alter a species in small ways, causing a population to change color or size over the course of several generations, according to The Natural History Museum . When this process happens over a relatively short period of time and in a species or small group of organisms, scientists call it " microevolution ."

Archaeopteryx, shown here in this illustration, is considered the first bird-like dinosaur on record, dating to about 150 million years ago during the Jurassic period.

But when given enough time and accumulated changes, natural selection can create entirely new species, a process known as "macroevolution," according to Derek Turner and Joyce C. havstad in " The Philosophy of Macroevolution ." This long-term process is what turned dinosaurs into birds , amphibious mammals (such as an animal called Indohyus ) into whales and a common ancestor of apes and humans into the people, chimps and gorillas we know today. 

Darwin also described a form of natural selection that depends on an organism's success at attracting a mate — a process known as sexual selection, according to Nature Education . The colorful plumage of peacocks and the antlers of male deer are both examples of traits that evolved under this type of selection. 

How did whales evolve?

One of the best examples scientists have of natural selection, is the evolution of whales . By using Darwin's theory as a guide, and understanding how natural selection works, biologists determined that the transition of early whales from land to water occurred in a series of predictable steps.

The evolution of the blowhole, for example, might have started with random genetic changes that resulted in at least one whale having its nostrils farther back on its head, according to Phys.org .

The whales with this adaptation would have been better suited to a marine lifestyle, since they would not have had to completely surface to breathe. Such individuals were more successful and had more offspring. In later generations, more genetic changes occurred, moving the nose farther back on the head.

Other body parts of early whales also changed. Front legs became flippers. Back legs disappeared. Their bodies became more streamlined, and they developed tail flukes to better propel themselves through water, according to the Natural History Museum .

Even though scientists could predict what early whales should look like, for a long time they lacked the fossil evidence to back up their claim. Creationists viewed this absence, not just with regard to whale evolution but more generally, as proof that evolution didn't occur, as pointed out in a Scientific American article .

An illustration of the semiaquatic

However, since the early 1990s, scientists have found evidence from paleontology , developmental biology and genetics to support the idea that whales evolved from land mammals. These same lines of evidence support the theory of evolution as a whole.

In the first edition of "On the Origin of Species," Darwin speculated about how natural selection could cause a land mammal to turn into a whale. As a hypothetical example, Darwin used North American black bears ( Ursus americanus ), which were known to catch insects by swimming in the water with their mouths open, according to the Darwin Correspondence Project .

"I can see no difficulty in a race of bears being rendered, by natural selection, more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale," he speculated.

The idea didn't go over very well with the public or with other scientists. Darwin was so embarrassed by the ridicule he received that the swimming-bear passage was removed from later editions of the book. Scientists now know that Darwin had the right idea but the wrong animal. Instead of looking at bears, he should have been looking at cows and hippopotamuses .

Other theories of evolution

Darwin wasn't the first or only scientist to develop a theory of evolution. Around the same time as Darwin, British biologist Alfred Russel Wallace independently came up with the theory of evolution by natural selection, according to the Natural History Museum . However this had little impact.

"The concept of evolution as a historical event was a hot topic among biologists and geologists prior to Darwin’s book because there was so much evidence accumulating, but I suspect biological evolution hadn’t really impinged on people outside of the academic bunker," Dr. P John D. Lambshead, a retired science research leader in marine biodiversity, ecology, and evolution at The Natural History Museum, London, told All About History Magazine . "As long as science knew of no mechanism to explain how evolution happened it could be safely dismissed as a crank idea."

Meanwhile, French biologist Jean-Baptiste Lamarck proposed that an organism could pass on traits to its offspring, though he was wrong about some of the details, according to the University of California’s Museum of Paleontology .

Like Darwin, Lamarck believed that organisms adapted to their environments and passed on those adaptations. He thought organisms did this by changing their behavior and, therefore, their bodies — like an athlete working out and getting buff — and that those changes were passed on to offspring. 

Maasai giraffe browses on leaves of a tall tree in the Maasai Mara National Reserve, Kenya.

For example, Lamarck thought that giraffes originally had shorter necks but that, as trees around them grew taller, they stretched their necks to reach the tasty leaves and their offspring gradually evolved longer and longer necks. Lamarck also believed that life was somehow driven to evolve through the generations from simple to more complex forms, according to Understanding Evolution , an educational resource from the University of California Museum of Paleontology .

Though Darwin wasn't sure of the mechanism by which traits were passed on, he did not believe that evolution necessarily moved toward greater complexity, according to Understanding Evolution — rather, he believed that complexity arose through natural selection. 

A Darwinian view of giraffe evolution, according to Quanta Magazine , would be that giraffes had natural variation in their neck lengths, and that those with longer necks were better able to survive and reproduce in environments full of tall trees, so that subsequent generations had more and more long-necked giraffes. 

The main difference between the Lamarckian and Darwinian ideas of giraffe evolution is that there's nothing in the Darwinian explanation about giraffes stretching their necks and passing on an acquired characteristic.

What is modern evolutionary synthesis?

According to Pobiner, Darwin did not know anything about genetics. "He observed the pattern of evolution, but he didn't really know about the mechanism," she said. That came later, with the discovery of how genes encode different biological or behavioral traits, and how genes are passed down from parents to offspring. The incorporation of genetics into Darwin's theory is known as "modern evolutionary synthesis."

The physical and behavioral changes that make natural selection possible happen at the level of DNA and genes within the gametes, the sperm or egg cells through which parents pass on genetic material to their offspring. Such changes are called mutations . "Mutations are basically the raw material on which evolution acts," Pobiner said. 

Mutations can be caused by random errors in DNA replication or repair, or by chemical or radiation damage, according to Nature Education . Usually, mutations are either harmful or neutral, but in rare instances, a mutation might prove beneficial to the organism. If so, it will become more prevalent in the next generation and spread throughout the population. 

In this way, natural selection guides the evolutionary process, preserving and adding up the beneficial mutations and rejecting the bad ones. "Mutations are random, but selection for them is not random," Pobiner said.

A molecule of DNA is coiled inside a cell nucleus.

But natural selection isn't the only mechanism by which organisms evolve, she said. For example, genes can be transferred from one population to another when organisms migrate or immigrate — a process known as gene flow. And the frequency of certain genes can also change at random, which is called genetic drift. 

The reason Lamarck's theory of evolution is generally wrong is that acquired characteristics don't affect the DNA of sperm and eggs. A giraffe's gametes, for example, aren't affected by whether it stretches its neck; they simply reflect the genes the giraffe inherited from its parents. But as Quanta reported , some aspects of evolution are Lamarckian.

For example, a Swedish study published in 2002 in the European Journal of Human Genetics found that the grandchildren of men who starved as children during a famine passed on better cardiovascular health to their grandchildren. Researchers hypothesize that although experiences such as food deprivation don't change the DNA sequences in the gametes, they may result in external modifications to DNA that turn genes "on" or "off."

Such changes, called epigenetic changes, do not modify the actual DNA sequence itself. For instance, a chemical modification called methylation can affect which genes are turned on or off. Such epigenetic changes can be passed down to offspring. In this way, a person's experiences could affect the DNA he or she passes down, analogous to the way Lamarck thought a giraffe craning its neck would affect the neck length of its offspring.

What is the evidence for evolution?

The Theory of Evolution is one of the best-substantiated theories in the history of science. It is supported by evidence from a wide variety of scientific disciplines, including  genetics, which shows that different species have similarities in their DNA . 

There is also evidence supporting the Theory of Evolution in paleontology and geology. This is through the fossil record, which shows how that species that existed in the past are different from those present today, according to Bruce S. Lieberman and Roger L. Kaesler in " Prehistoric Life: Evolution and the Fossil Record " (Wiley, 2010).

There is also evidence for Darwin's theory found in developmental biology . It has been discovered that species that seem very different as adults pass through similar stages of embryological development, suggesting a shared evolutionary past, according to the open-access textbook " Concepts of Biology ." 

Evidence for whale evolution from paleontology

Ambulocetus natans swimming underwater.

The critical piece of evidence was discovered in 1994, when paleontologists found the fossilized remains of Ambulocetus natans , which means "swimming-walking whale," according to a 2009 review published in the journal Evolution: Education and Outreach . Its forelimbs had fingers and small hooves, but its hind feet were enormous relative to its size. The animal was clearly adapted for swimming, but it was also capable of moving clumsily on land, much like a seal.

When it swam, the ancient creature moved like an otter , pushing back with its hind feet and undulating its spine and tail.

Modern whales propel themselves through the water with powerful beats of their horizontal tail flukes, but A. natans still had a whip-like tail and had to use its legs to provide most of the propulsive force needed to move through water.

In recent years, more and more of these transitional species, or " missing links ," have been discovered, lending further support to Darwin's theory. For example, in 2007, a geologist discovered the fossil of an extinct aquatic mammal, called Indohyus , that was about the size of a cat and had hooves and a long tail. 

Scientists think the animal belonged to a  group related to cetaceans such as Ambulocetus natans . This creature is considered a "missing link" between artiodactyls — a group of hoofed mammals (even-toed ungulates) that includes hippos, pigs, and cows — and whales, according to the National Science Foundation . 

Researchers knew that whales were related to artiodactyls, but until the discovery of this fossil, there were no known artiodactyls that shared physical characteristics with whales. After all, hippos, thought to be cetaceans' closest living relatives , are very different from whales. Indohyus , on the other hand, was an artiodactyl, indicated by the structure of its hooves and ankles, and it also had some similarities to whales, in the structure of its ears, for example.  

Evidence for whale evolution from genetics & developmental biology

The last shore-dwelling ancestor of modern whales was Sinonyx, top left, a hyena-like animal. Over 60 million years, several transitional forms evolved: from top to bottom, Indohyus, Ambulocetus, Rodhocetus, Basilosaurus, Dorudon, and finally, the modern humpback whale.

Genetic evidence also supports the idea that whales evolved from land mammals and provides information about the exact branching of the evolutionary tree. For instance, in 1999, researchers reported in the journal Proceedings of the National Academy of Sciences that according to genetic analysis of " jumping gene " sequences, which copy and paste themselves into genomes, hippos were whales' closest living relatives. Before 1985, researchers thought pigs were more closely related to whales, but this 1999 study overturned that idea, as the Associated Press reported. 

In 2019, researchers reported in the journal Science Advances about which genes within the whale genome were inactivated during the process of the creature's evolution from land mammals, as Science Friday reported. The researchers could tell that certain genes, including one involved in making saliva, had been inactivated because there are remnants of them, which the researchers call genomic fossils, in whale genomes. This indicates that whales evolved from a salivating creature.  

There's also evidence of cetacean evolution from developmental biology. Developmental biology illustrates the fact that animals that are very different as adults share similarities as embryos because they are evolutionarily related. For example, as embryos, cetaceans started to develop hind limbs, which disappear later in development, while the forelimbs remain and develop into flippers, according to the journal Evolution: Education and Outreach . This suggests that cetaceans evolved from a four-legged ancestor.

Is the theory of evolution controversial?

Despite the wealth of evidence from the fossil record, genetics and other fields of science, some people still question the theory of evolution 's validity. Some politicians and religious leaders denounce the theory, invoking a higher being as a designer to explain the complex world of living things, especially humans.

School boards debate whether the theory of evolution should be taught alongside other ideas, such as intelligent design or creationism. 

Mainstream scientists see no controversy. "A lot of people have deep religious beliefs and also accept evolution," Pobiner said, adding, "there can be real reconciliation."

Evolution is well supported by many examples of changes in various species leading to the diversity of life seen today. "Natural selection, or to put it another way — variation, heredity, and differential fitness — is the core theory of modern biology," John Lambshead explains. "It is to biology what, say quantum mechanics and special relativity are to physics or the atomic model is to chemistry."

Additional reporting by contributors Alina Bradford, Ashley P. Taylor and Callum McKelvie

  • The National Oceanic and Atmospheric Administration has a presentation on whale evolution.
  • To read the theory in its original form, see Darwin's book, " On the Origin of Species ."
  • Check out this article for an overview of natural selection.
  • To understand the difference between a theory and fact, see this National Academy of Sciences website .

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essay on charles darwin theory of evolution

Charles Darwin's Papers Online

For decades available only to scholars at Cambridge University Library, the private papers of Charles Darwin, one of the most influential scientists in history, can now be seen by anyone online and free of charge. This is the largest ever publication of Darwin papers and manuscripts, totalling about 20,000 items in over 100,000 electronic images.

This vast and varied collection of papers includes the first draft of his theory of evolution, notes from the voyage of the Beagle and Emma Darwin's recipe book .

We are extremely grateful for the kind permission of Cambridge University Library to reproduce these online. (See the Cambridge University Library Order Form for Digital Images .) They are presented in the same sequence as the original catalogue, which was divided mostly into bound volumes, each with a library classmark.

History of the material: The Darwin family and the Pilgrim Trust presented a magnificent collection of Darwin's papers to Cambridge University Library in 1942; they were delivered after the war. As the 1960 Handlist describes:

They were in parcels each containing small packets of manuscript wrapped in tissue paper on which the subjects had been noted in Darwin's hand. They were presumably just as Darwin left them, and accordingly this arrangement was preserved when they were bound, the volumes now representing as closely as possible Charles Darwin's papers in the order in which he left them. Beside the original papers there were copies of a large number of letters to Darwin, collections of press-cuttings, etc.

Notes on Galapagos animals

The immense value of this vast collection of material far exceeds the disadvantages of the occasional unreadable image and the lack of full colour. Several million pounds and years of production would be needed to produce colour digital images of the Darwin Archive. Hopefully this will eventually be achieved. In the meantime, most of the world's finest collection of Darwin's original manuscripts is now available for all to read, study and explore online and free of charge.

For an overview of Darwin's papers click here .

Darwin Online cannot give permission to reproduce Darwin manuscripts; enquiries about this should be addressed to Adam Perkins, Curator of Scientific Manuscripts in the University Library ( [email protected] or [email protected] )

Many individuals and institutions have helped to make Darwin Online possible, for a complete list see Acknowledgements .

The papers can be found in two ways:

1. Browse through whole volumes of Darwin's papers . Click here . 2. Search the catalogue for specific items, people, dates etc . Click here .
Darwin's first recorded doubt in 'the stability of species', from his Galapagos bird notes from the voyage of the Beagle , 1836 First sketch of the theory of evolution, 1842     Theoretical notebooks.     Drafts of Descent of Man Review of Origin of Species , 1859 Emma Darwin's recipe book. Darwin family photos

Selections from the Darwin papers

•  The first drafts of Darwin's theory of evolution: the 1842 sketch and 1844 essay. •   Darwin's papers from the Beagle voyage. Click here . •   Darwin's religious views: Emma Darwin's 1839 memo , and an entire volume on the subject. Click here . •   Drafts of Darwin's unpublished 'big book', Natural selection. Click here . •   Notes & drafts for his book Descent of Man . Click here . •   Unpublished photos collected for Expression of the Emotions . Click here . •   Reviews of Darwin's works. Click here . •   Darwin and experimentation on animals. Click here . •   Caricatures, cartoons & sketches of Darwin. Click here and here . •   Darwin's accounts with his publisher John Murray for 1881. Click here . •   Obituaries of Charles Darwin, Click here , here and here . •   Items in French , German , Spanish or Italian .

See a list of all available online images of Darwin's papers. Click here .

See Darwin's handwriting beside a typed version:

[ Beagle animal notes (1832-33)]. Text & images 'Chiloe Jan r . 1835' [ Beagle notes]. Text & images 'The position of the bones of Mastodon (?) at Port St Julian is of interest'. Text & images [Darwin's personal 'Journal' (1809-1881)]. Text & images [An autobiographical fragment] (08.1838). Text & images 'Our poor child, Annie' [Darwin's reminiscence of Anne Elizabeth Darwin] (30.04.1851). Text & images Part of Darwin's 'autobiography', 1876

The collection is organized into categories:

•   Abstract — Darwin's reading notes. •   Draft — Darwin's rough drafts of his many publications. •   Figure — Drawings, diagrams and tables. •   Note — Includes most of Darwin's notes, usually organized into subject portfolios. •   Photo — Photographs. •   Printed — Published items such as reviews of Darwin's works or clippings he collected for his researches. •   Miscellaneous  

Read about the reception of the launch of Darwin's papers here .

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Charles Darwin

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Charles Darwin lived between 1809 and 1882. He was an English geologist and naturalist. He is recognized for the evolution theory that he has established. Darwin brought the idea that all organisms originated from a common ancestor. He believed that evolution came from natural selection as organism struggle to exist. Darwin believed that only the fittest organism is able to survive, and their genes are moved to the next generation. The theory of natural selection was formulated by Charles Darwin in the 19th century. Darwin was an English geologist, biologist and naturalist. Darwin started his investigation on species on the islands using vessel HMS Beagle. He spent time on the islands and came up with a theory that contradicted the creation theory. Darwin concluded that all species originated form a common ancestor, through natural selection process. Natural selection is the largest factor that resulted to the diversity of species as well as their genomes.


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Darwins Theory of Natural Selection

Darwins theory is traced back to the time of Aristotle. Darwin pointed out that he borrowed some ideas from the works of Aristotle and other Greek Thinkers such as Empedocles. Darwin pointed out that he could not have discovered how evolution took place without the work of Robert Thomas Malthus who made him realize that organisms adjust as they try to fit in the competition for scarce resources.

Charles Darwin is regarded as the father of revolutionary biology as he introduced the evolution theory that describes the origin of species. Darwins scientific theory argues that populations develop over time through the natural selection process. His works proved that diversity of life arises through common descent evolution pattern. Darwin gathered information for his theory in the 1830s on the Beagle voyage. He also conducted subsequent experimentation, correspondence and research that proved his theory.

Explanation of Natural Selection

All species have an aim of reproducing to survive. They pass genetic information from one generation to another. Through reproduction, species produce more offspring such that the environment cannot handle it. As a result of increased reproduction, the population increases. The species living in a particular environment start competing for the scarce resources. Some of the offspring cannot survive because the competition becomes tougher and tougher as the amount of competitors increases.

Survival for the Fittest

As a result of the competition, some of the organisms die, leaving the tough ones to survive. Organisms that are best fitted for the environment mange to survive. When the environment provides such complicated conditions, some of the animals still manage to survive while some perish. Darwin believed that evolution came from natural selection as organisms struggle to exist. He pointed out that only the fittest organisms are able to survive, and their genes are moved to the next generation

Organisms that manage to survive the tough environment develop desirable characteristics that allow them survive in such environment. They have a suitable genome that makes them adjust to the environment by attaining suitable characteristics for the environment. The organisms pass the desirable characteristics to their offspring through their genes. A new species is created through evolution as organisms try to adjust to the environment.

According to Darwin, the evolved organisms start living in an ecological niche that favours their survival. These organisms continue passing adjusted features to their offspring in order to increase chance of survival. When the population of the organisms living in a particular ecological niche increases beyond what the environment can handle, the theory of natural selection continues acting. An organism that cannot survive in the harsh environment dies because of the competition for the scarce resources. This leaves the survivors with adjustment as the only option. They develop suitable characteristics that make them survive in the environment. They pass their adjusted features to their offspring, giving a rise to new species.

Impact of Natural Selection Theory

Most scientists are convinced that Darwin was the greatest scientist who had the revolutionised ideas. He managed to convince scientists that evolution originated form descent modification. His theory has been used to develop scientific drugs, genetically modified organisms and pesticides among other biological elements. His evolutionary synthesis has been incorporated with Madelia genetics, population genetics and natural selection ideas to evolve the world. It is Darwins ideas that reference modern scientific theories.

Darwin is the founder of evolution theory that shows how organism evolved. He explained how evolution occurred through natural selection. He did a lot of researches that resulted to a conclusion that all organisms originated from a similar ancestor. He believed that competition for the use of scarce resources such as food makes animals to adjust so that they can defeat the others. Only those that fit the best win the race. This adjustment is caused by natural selection, leading to evolution. New species arise from the adjusted parents with inheritable variations.

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Charles Darwin: Theory of Evolution

An outline to the essay.

This essay consists of an introduction, the theory, its impact, and a conclusion. The introduction talks about the journey of Charles Darwin that lasted for around two years in the ship HMS Beadle, the emergence of the Darwinism theory, along the individual that influenced the development of this theory. The main part of the essay is its body. This begins with the main factors that show the existence of evolution in this world. These factors indicated the presence of evolution and lead to the assumptions.

The next section is the theory itself, or the main postulates of the theory, which later called Survival of the fittest. The three basic things to understand regarding evolution namely, DNA, the quantity of DNA taking part in the change, and the effect of the environment on evolution, have been exhausted by this research paper. Next, the research paper has examined the seven stages of evolution recognized.

The study has examined solid evidence about the existence of evolution has also been examined, followed by arguments presented by different critics of Charles Darwin’s theory, and how they have been countered, until today. The paper then concludes by outlining an overview of the actual study.


Not many books have caused as much uproar as the Origin of Species by Charles Darwin. This book was originally published in 1859 under the title, on the origin of species by means of natural selection or, The Preservation of favored races in the struggle for life (Darwin 2004, 56). The whole book and theory, if broken down into simplistic terms, just say that all living things developed from a single ancestor, and complex things developed from simple things. Over time, the genes of living things undergo genetic mutation, and the beneficial alterations were kept, which the author termed ‘natural selection’. These beneficial alterations were then passed on to the next generation and the process is continuing ( Darwin’s theory of evolution 2009, par. 3). The theory had such a profound impact on the world of biology that the phrase “nothing makes sense in biology except in the light of Theory of Evolution” came into existence. Darwin’s Theory of Natural Selection has engendered the “Darwinian Revolution”. Along with Darwin, his close associate, Alfred Wallace is also given credit for the theory. While traveling aboard the HMS Beagle for over two years, Wallace observed the fossils in South America, the Ostriches of the pampas, and the finches in the Galapagos Islands that triggered the research, leading to the proposition of the theory of Natural Selection .

The Theory and its Implications

Darwin and Wallace based their assumptions on seven basic factors that proved the existence of natural selection. These are Geology, Fossils, Island life, Overproduction of individuals, and extensive variation seen in individuals. These variations were inheritable and effects of artificial selection. It was found that geological procedures have been consistent throughout time, an indication of how considerably old the earth is. A glance at the present is enough to see the dynamics that shaped the past. Even slight changes that go on for a long period of time could have a large-scale impact, on Biology . Even though extinct, certain forms show a distant connection with the ones living, and this implied a thread of evolution running through both. While studying Galapagos Islands, it was found that the species within the islands were slightly different from their counterparts on the mainland. This led to the conclusion that the species that live on islands evolve in isolation, and thereby evolve slightly differently. According to Malthus, it was found that species reproduced exponentially. Even though offspring abounded, most of them did not reach maturity. This indicated a process of selection in which once members of an offspring reached maturity, reproduction would then occur. They also found that there were considerable variations within the individuals of a species. Both being taxonomists, they found that even the wild species were not an exemption. These differences were also innate. Even physiological traits, textures and body shape, vulnerability to certain types of diseases, etc., were also found to be inherited. While examining the methods of artificial breeding and their effect on domestic animals, it was found that some variations were favored and others were disfavored. Others were neutral even. These observed facts guided Darwin towards the theory of evolution and the principle of Natural Selection (Johnson 2008, par. 2). The Theory indicates that if a population of a particular species developed a functional advantage, like learning to fly, the progeny of that particular individual species would inherit this functional advantage, along with the successive generations. The inferior ones that remain behind would gradually die out. Natural selection means that the functional advantage of any particular species would be preserved and the remaining inferior members of the species would die out, leaving only the superior ones. This is very much like domestic breeding, where only the superior quality of a species is allowed to breed, leaving out the inferior ones. Natural selection singles out and discards the inferior members of a breed over time. The implication here then is that only those that are fittest would survive. Here, fitness means reproductive success [Darwin did not coin the term, Survival of the fittest’]. Darwin also wrote that these changes could not take place in giant leaps; rather, they would only occur progressively. Therefore, if any species contained a complex organ that could not have been formed by numerous, slow, and successive steps, this would have jeopardized the theory that Darwin so strongly supported. Such changes could also not take place in the individual members of a population but would happen to the whole population over periods of time.

Darwin states that the whole species must have developed from a common ancestor, which was the simplest organism, and from an event that took place by random chance. This, according to Darwin, is what resulted in the first form of life on earth. It is the development from simple to comple.

While one is examining the process of natural selection, there is a need to put into consideration three basic things:

  • We need to know that only heritable variations are amplified or diminished. This is because of the controlling role of genes in these variations. Evolution happens because of the ability of genes to mutate. Genes are actually chemicals that contain coded information in the form of DNA. Though gene mutations are random, natural selection involving other factors happens.
  • The whole population of a species gets involved in the process of Natural Selection as opposed to a single species.
  • The process of natural selection depends on the environment. When the environment is friendly to a particular aspect of the species, members of a species that are not comfortable with the aspect in question end up reducing in numbers. If the environment alters, the species could return to its original habitat.

Under favorable environmental conditions, species variations due to natural selection could give rise to phenotypes.

One of the consequences of species variation due to natural selection is adaptation. Genetic reasons are believed to play a role in species variations and adaptations to the environment, as a result of Natural selection.

While considering the evolutionary chain, only the evolution between organic creatures is usually reflected. If we expand this universally and try to indicate the universal evolution cycle into this, we could divide the whole evolutionary chain into seven stages: Cosmic evolution, stellar evolution, chemical evolution, planetary evolution, organic evolution, macroevolution, and microevolution. Out of these seven stages, only the last evolution (microevolution) may be observed, according to scientists, while the rest are just assumptions.

Nevertheless, even though evolution is not observable directly, there is evidence that proves the theory to be true. First, we have to consider fossil evidence. While arranging fossils chronologically, we can notice a gradual change in the structure and formation of characteristic limbs of several species. For example, horses as a species show a very evident evolutionary trait. There is also proof to suggest that natural selection can evidently produce evolutionary change. It has been pointed out that birds like the finches [Darwin’s finches of the Galapagos Islands] are favored to have stouter beaks when only dry seeds are available to them.

Artificial studies indicate that evolution favors natural selection. Through research, we find evidence that points at the natural selection in other fields of Biology. A case in point here would be the anatomical record where organisms that share a common ancestry are found. The Molecular record indicates that the genes of organisms shown to be closely related by fossil records are also more similar than the ones distantly related.

Evidence also indicates that there are body parts that have been found to be remnants of our evolutionary past like the appendix and the tonsils, amongst others. These body parts have been found to have had no evident function at all within the body, but they still existed.

A century and a half after the publication of the controversial book by Darwin, this publication still holds its relevance in helping to better understand the field of evolution. The theory of evolution as championed by Darwin has raised many controversies. Darwin’s critics mainly raise the following objections to his theory.

  • First the ‘theory’ is just a theory. There is no solid ground for the theory. We are not certain about the facts given in the books and in science, theory means the basis on which we can rely on. Critics argue that this argument has lost ground because even the theory of gravity is hypothetical too.
  • Another thing pointed out at the time, was the absence of the fossil intermediaries. However, this argument has lost ground in recent times because the absent fossils have been dug up.
  • There is the argument regarding what Darwin himself has said in his book, that it was difficult to imagine that the eye had developed with intermediaries, which he felt to be ‘irreducibly complex’. Even this argument has broken up because intermediate eyes have been dug up. These intermediaries arose upon the discovery of light, and it was better than not being able to identify it at all.
  • The next argument is that the order of things is usually lost by the occurrence of random events as, stated in the second law of thermodynamics. However, the complete law stated is that of a closed system and the earth, which receives energy continually from the sun, and is therefore not a closed system at all.
  • The formation of proteins by chance is a technical improbability, as Darwin’s opponents have stated. However, this argument was also proved wrong, in that the probability theory cannot be used to argue backwards.
  • Another case is that Natural selection does not entail evolution. For example, there is nowhere that we find a fish developing wings and leaping away from predators in any of the experiments that have been conducted. Nonetheless, biologists argue that even in the case of lab experiments with dogs, breeds that cannot interbreed have been produced. This is also the case with evolution. Radically different species like fish and amphibians did have a common ancestor, a claim that is readily supported by available fossil records.
  • The argument of such critics as the reducibly complex argument goes for the improbability of the complexity of a cell which cannot be explained by evolution from simpler stages. They seem not to understand that this happened eons ago and was set up stage by stage. The complex blood clotting system took nearly 600 million years to be fully formed. However, some varieties of fish retained the formative blood clotting system before its increase in complexity, to reach where it is today.
  • Body parts, with no evident functionality, have recently been found to have had uses that were unknown in the past. This too, is an assertion made by critics of the theory of evolution, according to Darwin. However, such arguments are baseless, and the new-found functions of body parts like the appendix are neither an indication of the fallacy of the theory of evolution, or a proof of it.

Even though the concept of evolution was nothing new to the world of science, nonetheless many scientists preferred this to the concept of creation; they were not able to give an explanation to the process of evolution. Thankfully, Charles Darwin, using his theory of natural selection, greatly assisted in shedding light on the concept of evolution. The theory of natural selection that Darwin postulated has been a source of intense debate since the publishing of his book, ‘The origin of species’, in 1859. Notwithstanding the debates and controversies that have surrounded this theory, it has stood the test of time, for these 150 years.

Charles Darwin viewed evolution as a constant struggle to bring out the fitter species. That every species fights for life, is a fact accepted by everyone. Neo-Darwinism tries to reconcile the problem of accommodating Gregor Mendel’s theory, which states that species cannot be altered, with the theory of natural selection. Darwin has also argued that use and disuse mechanisms could be responsible for functional wing loss in selected insects dwelling in islands, indicating that natural selection could be at play here. Darwin was also convinced that environmental factors could be responsible for inheritable variations that were manifested by species. Even with the number of tens of thousands of ‘irreducibly complex’ systems at the cellular level, the cards pass on and on to both sides of the table.

Many are the times when people believe and accept that Darwin’s theory is the most acceptable for evolution. However, they do not go further to state that it does not prove evolution.

There have been many significant evolutionists in modern times who have revised the Darwinian theory of evolution. Under the light of modern inventions and developments in molecular science, the Darwinian science of evolution is now taking flight with new wings adapted for the horizon.

Bowler, Peter. J. 2003. The History of an Idea (3rd Ed.). California: University of California Press.

Campbell & Reese. Principles of Evolution. Web.

Darwin, C. The Origin of Species. London: Collectors library, 2004.

Darwin’s theory of evolution- A theory in crisis. 2009. Web.

Evidence for evolution- Controversial data. 2009. Web.

Evolution: Darwin’s theory. 2009. Web.

Johnson, George. 2008. The Evidence for Evolution. Web.

Johnson, George.2008. Backgrounders. Web.

Quammen, D. 2006. The reluctant Mr. Darwin . New York: Atlas Books.

Theory of Evolution. 2009. Web.

Thomas Huxley. 2009. Web.

Wallace & Darwin. Principles of Evolution. 2009. Web.


Proof of evolution of toothed whales from land-living hoofed animals.


Evolution of flat small shelled oysters to large flat shelled ones in a period of 12 million years.


Fossil record of the evolution of horses from Hyracotherium to Equus. There are long periods of small change and small periods of great change.


Darwin’s sketches of the Galapagos finches:

  • Large ground finch Geospiza magnirostris;
  • medium ground finch Geospiza fortis;
  • small tree finch Camarhynchus parvulus; 
  • warbler finch Certhidea olivacea.


Evidence that natural selection alters beak size in Geospiza fortis.


These photographs show color variants of the peppered moth, Biston betularia. Tutt proposed that the dark moth is more visible to predators on unpolluted trees while the light moth is more visible to predators on bark blackened by industrial pollution


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