The Descent of Man | Study Guide

Charles Darwin

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The Descent of Man | Chapter 7 : On the Races of Man | Summary



Darwin questions the value of identifying the differences between races from a classification point of view. Naturalists examine the differences between allied forms in order to rank and organize them, and the most valued information is consistency of character and features that remain distinct for a long time. He admits we are influenced in our judgment of people by skin color, hair, and slight differences in features but asserts that even the most distinct races of man are more alike in form than one might suppose.

Darwin first looks at the case for classifying humans by race. He says a naturalist comparing "Negros" (his term for those of African descent), Mongolians, and Australian Aborigines would acknowledge the perceived differences, note the widely different climates they live in, and look for differences in body structure. The naturalist would examine the external parasites (such as lice) affecting each group because different types of parasites live in different areas of the world. He would look at fertility trends when the races are mixed. Darwin notes that mixed-race children in Africa can appear black, white, and even "piebald" (having irregular patches of skin color). In the United States mixed-race children often appear more blended. Ultimately, a naturalist might justify classifying races based on distinguishing differences that have remained constant for a long period of time.

Darwin then takes up the case for not classifying humans by race. If a naturalist looked at whether races remain distinct when mingled together in large numbers in the same place (as is the case with ordinary species), they would realize the answer is no. Distinctive characteristics of all races are highly variable (e.g., skull shapes), and a naturalist can't classify species by inconsistent characteristics. Also, according to Darwin, all races of man graduate into each other and have intercrossed throughout evolution, sharing far more similar structural characteristics than differences. Darwin notes that some naturalists have suggested the term subspecies as a way of classification. He thinks this might have some value as a term to describe forms that are closely related by characteristics yet display some obvious variation.

Darwin explains that some anthropologists debate whether humankind is monogenist (one original species) or polygenist (many original species). But discoveries by these scientists have shown that arrowheads from completely different places in the world are virtually identical, suggesting, as Darwin believes, that humans evolved from a single primitive form. He cites a study that shows great similarities between all races in taste, disposition, and habits. The study found activities such as dancing, making music, celebrating, using language, and even making facial expressions are remarkably similar despite differences in race.

The partial or complete extinction of races of man have occurred over time. Man can endure extremely unfavorable conditions (severe heat, cold, etc.), but extinction was most likely the result of wars between tribes or races, famine, infanticide, illness, and infertility (the last two being the most potent causes). Races have also been fatally affected by colonization. Illness often occurs when two races encounter each other for the first time, because each is not immune to the parasites and diseases that are native to the others' environment. But colonization has had other ill effects that can greatly reduce the population of a tribe. Darwin uses the example of the Sandwich Islands (now known as the Hawaiian Islands). British explorer James Cook discovered the islands in 1778. The island population was 300,000. Forty years later, the population was 51,000—a 68% decrease. The decrease was attributed to the following:

  • bloody wars
  • severe labor imposed by colonists
  • child mortality
  • newly introduced diseases
  • lessened fertility (fewer total births, more males born)

Lower animals provide similar examples of how races are affected by external (climate) forces. Wild animals that are captured are more susceptible to infertility; domesticated animals are more fertile when contained. Civilized humans resemble domesticated animals—they are better able to resist all manner of change than their more savage counterparts.

Darwin examines the formation of races, suggesting that the crossing of races will sometimes lead to new races, which can become homogenous over time. While some thought skin color was affected by climate, examples such as the Dutch, who have lived in South Africa for over 300 years, appear to refute the idea. Darwin points out that questions of immunity in the races are probably partly inherited. He cites the "Negro" immunity to fevers found along the African shore (which killed one-fifth of the white settler population there) as well as tropical fevers in North America. Of course, this immunity is not related to skin color—it is determined by blood, tissues, and the nervous system. Darwin mentions the importance of sexual selection in humans' heredity history and development, and he suggests that the distinctions people make about race are more a result of sexual selection and heredity than of natural selection. This points to the following two parts contained in The Descent of Man; and Selection in Relation to Sex, which explore man's and animals' hereditary characteristics.

Darwin closes this part of the book by publishing an article by Thomas Henry Huxley, a British biologist who agreed with Darwin's theory of evolution and natural selection. Huxley was called "Darwin's Bulldog" because he strongly argued in print and in public for the ideas Darwin advocated. "Note on the Resemblances and Differences in the Structure and the Development of the Brain in Man and Apes" (1874) is an argument in support of man and apes' descent from the same progenitor. Huxley examines the structural similarities between the two brains and provides vigorous arguments against detractors of Darwin's theory of evolution. Huxley writes that the "difference between the brain of the chimpanzee and of man is almost insignificant."


It seems fairly clear that Darwin does not agree with naturalists who suggest that humans should be divided into classifications based on their skin color, partly because he felt his theory of evolution simply doesn't support such an idea and partly because he felt that some people were using classification to promote ideas about racial superiority. Darwin found the institution of slavery to be detestable, and this chapter appears to be an effort to undermine acceptance of racial classification by presenting research that shows all humans came from the same single progenitor.

Darwin first presents the argument for classification by race, describing some of the investigations a naturalist might engage in to determine if the idea was legitimate. He does this to set up the next section, where he clearly refutes the main ideas naturalists promoting racial classification have used. He suggests that a naturalist who looks at the available evidence would have to determine that classifying species by inconsistent characteristics fails the scientific method.

Darwin examines how races become extinct (or nearly extinct), as some have over time. He offers no simple explanation for this phenomenon, but he catalogues some of the commonalities that decimate entire populations. Severe change in environment, wars, disease, colonization, and lessened fertility all play recurring roles in tribes or communities that have become extinct. Moving people from their indigenous environment to a completely different environment is a common cause of population depletion. While some of these transplanted people are able to survive, diseases found in the new environment often take a fatal toll. Additionally, as he discussed in an earlier chapter, human adaptation to new conditions often takes generations to occur.

Darwin returns to the topic of race to discuss the mixing of races and how inherited characteristics can remain prominent or change into a new characteristic. He uses the research on immunity to certain diseases in "Negros" who have been moved far from their indigenous environments to other parts of the world. He makes the point that skin color doesn't determine what diseases "Negros" are immune to—it's their blood and hereditary makeup that do so. To modern readers Darwin's casual use of certain racially offensive terms and assumptions about different races may seem startling. But in the mid-1800s even a naturalist such as Darwin, who opposed the institution of slavery, used such language regularly.

It should be noted that Darwin's suggestion that skin color is unaffected by the climate is known today to be somewhat erroneous. Scientists today know that skin color is a reflection of sun exposure. While skin color will not dramatically change in a population that moved to a new area even 300 years ago, when considered on a longer-term evolutionary time scale of tens of thousands of years, human populations that exist in areas with a high degree of sun exposure will have darker skin than populations that exist in areas with minimal degrees of sun exposure. In sunlight-heavy areas, individuals with more of the skin's pigment called melanin are protected from the harmful effects of the sun. In sunlight-low areas, paler skin is able to absorb more sunlight and vitamin D.

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