Charles Darwin's Descent of Man was published on February 24, 1871. So this year is the 150th anniversary of its publication. This has prompted some recent articles--including a particularly good one by Richerson, Gavrilets, and de Waal (2021) in Science--and a book edited by Jeremy DeSilva (2021) assessing Darwin's account of human evolution Descent in the light of modern evolutionary science.
On some points, we can see that Darwin was mistaken. For example, he claimed that because of their distinct roles in the sexual division of labor, women were intellectually inferior but morally superior to men. In 1875, only four years after the publication of Descent, Antoinette Brown Blackwell showed that Darwin's evidence did not support his conclusion about the intellectual inferiority of women, and that the correct inference from the biological facts was that the sexes are "true equivalents--equals but not identicals." I have written about this in Darwinian Natural Right (123-160).
His most fundamental mistake was in trying to explain the inherited transmission of parental traits to their offspring through the "hypothesis of pangenesis"--the idea that every part of the body emits tiny particles ("gemmules") that migrate to the gonads and then are transmitted to offspring, so that the gemmules develop into their associated body parts as the offspring matures (Darwin 2004, 264-267). Unfortunately, Darwin knew nothing about Gregor Mendel's experiments that provided the first evidence for genetic inheritance. Mendel knew a lot about Darwin, however, and he agreed with Darwin's theory of evolution. In his handwritten annotations in his copies of Darwin's books, Mendel endorsed most of Darwin's reasoning, while correcting what he said about pangenesis (Fairbanks 2020). In his annotations of The Variation of Animals and Plants Under Domestication, Mendel highlighted those passages where Darwin admitted that pangenesis was "merely a provisional hypothesis or speculation," and that "the existence of free gemmules is a gratuitous assumption." Mendel was an Augustinian friar, and he was condemned by those in the Catholic Church who regarded his support for evolution as a denial of the Catholic doctrine of Creation.
For me, rereading The Descent of Man today is instructive in two ways. First, while some evolutionary biologists have criticized the "modern evolutionary synthesis" as being too "gene-centric" in not recognizing the importance of cultural evolution, most of what they have proposed as part of an "extended evolutionary synthesis" can be found in The Descent of Man. In particular, Darwin stresses the importance of cultural evolution, including moral evolution, for explaining human biological nature. This is what Richerson, Gavrilets, and de Waal mean in saying that Darwin's Descent "foreshadowed" modern theories of human gene-culture coevolution. I have written about this in previous posts here and here.
Darwin's Descent is also instructive for me because it largely supports what I have called "biopolitical science," which requires a three-levelled analysis of political history as showing the unity of political universals, the diversity of political cultures, and the individuality of political judgments. I have worked through these three levels of biopolitical history as they are generally manifested in human politics and as they were particularly illustrated in Abraham Lincoln's decision to issue the Emancipation Proclamation in 1863 (Arnhart 2012). This idea of biopolitical science first came to me in 1986 when I read Jane Goodall's Chimpanzees of Gombe, and I saw that this was a political history of the chimps at Gombe showing the natural history of chimpanzee politics, the cultural history of this particular chimpanzee community, and the biographical history of the unique individuals in that community. I have written some posts on this here, here, and here.
I have argued that a Darwinian social psychology needs to understand the interaction of genetic history (the evolutionary psychology of Tooby and Cosmides), cultural history (the cultural group selection of Richerson, Boyd, and Henrich), and biographical history (the evolved personality and life history of self-interested individuals who are agents of cultural change acting through coercion or persuasion, as presented by Singh, Wrangham, and Glowacki).
There is a complex coevolutionary interaction between these three levels of history. Genetic history enables and constrains, but does not determine, cultural history. Genetic history and cultural history jointly enable and constrain, but do not determine, biographical history.
"The more efficient causes of progress seem to consist of a good education during youth whilst the brain is impressible, and of a high standard of excellence, inculcated by the ablest and best men, embodied in the laws, customs, and traditions of the nation, and enforced by public opinion. It should, however, be borne in mind, that the enforcement of public opinion depends on our appreciation of the approbation and disapprobation of others; and this appreciation is founded on our sympathy, which it can hardly be doubted was originally developed through natural selection as one of the most important elements of the social instincts" (2004, 169).
At the level of natural history, natural selection has shaped the innate social instincts of human beings, which make them sensitive to the approbation or disapprobation of people in their community. At the level of cultural history, this concern for social conformity motivates human beings to learn the social norms of their group. At the level of individual history, those talented individuals with persuasive influence or authority over the group can select the social norms that will be enforced by public opinion.
After Darwin, for a long time, many biologists were not interested in studying the evolution of individual animal personalities, because they assumed that evolution would shape a species typical psychology shared by all individuals of the species with little heritable variation. Evolutionary psychologists (like Leda Cosmides and John Tooby) have concentrated on human universals as evolutionary adaptations shared by all human individuals.But in recent decades, the biological study of animal personalities has become one of the hottest topics in biology. One of the most extensively studied models of human personality among psychologists is the Five Factor Model that describes human personality differences across five domains--Openness to Experience, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (OCEAN). Each domain corresponds to an axis running from high to low. So, for example, those individuals high in Agreeableness tend to be helpful, trusting, and cooperative with everyone. Individuals lower in Agreeableness tend to be less helpful, more suspicious of others, and more competitive than cooperative.
This same Five Factor Model can be applied to the study of nonhuman animal personalities, using the same methods as are used in studying human beings. Four of the factors appear in many animal species. But Conscientiousness seems to appear only among chimpanzees and human beings. One possible explanation for this is that Conscientiousness requires a high cognitive ability for making plans and controlling impulses in executing those plans, which requires the large frontal lobes found only in chimps and humans.
The five factors of personality have been found to be highly heritable and thus genetically influenced. But these factors also vary according to environmental experience, particularly the environment of early experience, which influences personality throughout life. So personality seems to arise from genetic predisposition, from environmental learning, and from the interaction of genes and environment (including the cultural environment). Through experimentation with animals in the wild and in laboratories, scientists can make testable predictions about the genetic and environmental causes of personality.