Review: The Descent of Man
- Published: 20 March 2012
- Written by Jenn Lindsay
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In Descent of Man Darwin lays out how his theory applies specifically to human beings, a pursuit too controversial and onerous for inclusion in his first book. Darwin’s goal “is to consider, firstly, whether man, like every other species, is descended from some pre-existing form; secondly, the manner of his development; and thirdly, the value of the differences between the so-called races of man.” He acknowledges that most naturalists of his time accept evolution and natural selection, but that the place of the human being in the animal kingdom is not yet laid out, nor has the human spectrum of physical variation and mental ability been carefully addressed. Notably, Darwin also roundly decrees that though humans may be delineated racially, they are all the same species, all descended from apes and other primates, their closest analogue in the animal world. The book is heavily cited and carefully weighs critiques against the theory of evolution, narrowing his argument through the specific theoretical lens of sexual selection. This argument sets Darwin apart from his “co-discoverer” of natural selection, Alfred Russell Wallace, who disputed sexual selection; much of Descent of Man is in response to opinions put forth by Wallace.
By charting the continuity of physical and mental attributes throughout the creaturely kingdom, Darwin sets the stage for his theory of sexual selection. While natural selection reflects adaptations for survival, sexual selection reflects adaptations for reproductive success. He first introduced sexual selection briefly in On the Origin of Species; Descent of Man covers both human and sexual selection extensively. Sexual selection theory operates by two means. “In the one it is between individuals of the same sex, generally the males, in order to drive away or kill their rivals, the females remaining passive; whilst in the other, the struggle is likewise between the individuals of the same sex, in order to excite or charm those of the opposite sex, generally the females, which no longer remain passive, but select the more agreeable partners.” Darwin felt behooved to give sexual selection an exhaustive treatment because natural selection alone could not account for evolutionarily expensive, non-competitive adaptations such as the peacock tail.
Descent of Man is presented in three parts. Part I, The Evolution of Man, addresses the evolution of physical and mental traits, natural selection and civilized society, and the debate of Darwin’s time on human race. He lists innumerable physical corollaries between humans and animals as evidence for the development of man from “some lower form,” and compares mental and emotional traits, including intellectual and moral faculties, between life forms. The final section addresses polygenism, a form of scientific racism that divides human races into distinct species; Darwin argues for monogenism, insisting that the races are but sub-species or variants.
Parts II and III cover sexual selection, outlining its basic principles via the facets of male-male competition and cases of female choice. Part II is devoted to sexual selection in animals, with chapters devoted respectively to insects, butterflies, fish, amphibians, reptiles, and (spanning four chapters) birds. Part III focuses on sexual selection in humans, citing numerous anthropological accounts of primitive societies to demonstrate that the most vigorous of men will draw the most attractive of women. Owing to his use of tools and his need for mental and physical superiority in the contest for selection, “man has ultimately become superior to woman…as the peacock is in ornamental plumage to the peahen.” Though women are dominant in choosing sexual partners, men dominate socially and mentally; “man is more courageous, pugnacious and energetic than woman, and has a more inventive genius.”
It is hard to know how much the supremacist patriarchal mores of Darwin’s time undergird his short shrift to women. He posits a biological basis for male superiority, but in humans this is social and does not manifest in the same sexual dimorphism found in peacocks and peahens. Readers of Descent of Man must bear in mind that Darwin employs racist and sexist language as the discourse of his time; it is jarring to the socially sensitive ear and it must be deliberately positioned. If this text is engaged as the precursor to Dennett’s and Dawkins’ evolutionary explanations of religion, it is fair to address Darwin’s seeming social biases. But he writes with no malice, vitriol, or infantilization of women and non-whites. In fact, he advocates for them. In contrast, Dennett and Dawkins spurn and antagonize religious believers; the tone is entirely different.
Charles Darwin broaches morality, often regarded as the purview of religion, though he is presciently aware that his work will likely be “denounced by some as highly irreligious.” However, he considers his work to be the natural extension of any biological investigation of the mechanics of natural childbirth, and is able to chart the moral sense “firstly, from the enduring and ever-present nature of the social instincts; secondly, from man's appreciation of the approbation and disapprobation of his fellows; and thirdly, from the high activity of his mental faculties, with past impressions extremely vivid.” Darwin ties moral acuity to reproductive advantage and the development of aesthetic instincts in human beings; he also argues in favor of the advantageous of charity and the handling of society’s weaker elements: “The aid we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts...if we were intentionally to neglect the weak and helpless, it could only be for a contingent benefit, with an overwhelming present evil.”
Descent of Man, despite its reliance on racial parlance of its day, is an accessible book, altogether inviting for non-specialists. The explanations of natural selection are not technical, but his convictions are confident, well-founded, and have played out as largely accurate as technology has allowed for more intricate demonstrations of his theories. Darwin comes across as a responsible and open-minded theorist, noting, “Many of the views which have been advanced are highly speculative, and some no doubt will prove erroneous; but I have in every case given the reasons which have led me to one view rather than to another.” Nevertheless his conviction about the common ancestry of the animal world has a solid foundation: “The grounds upon which this conclusion rests will never be shaken, for the close similarity between man and the lower animals in embryonic development, as well as in innumerable points of structure and constitution, both of high and of the most trifling importance...are facts which cannot be disputed.”
Darwin extrapolates his evolutionary theory beyond the natural sciences and into psychology, ethics, and social evolution. The technical capabilities of his time, and the solitude of innovation that precedes scientific corroboration, precluded a minute parsing of the process of evolution. But even after 150 years the biggest question about evolution remains: the dilemma of incipient stages. Darwin seems fairly invested in describing evolution as a random, inefficient, accidental process, but time and again describes it as if it really is breeding pigeons, as though it has a teleology. He doesn’t pay as much attention to maladaptive mutation as he should, because there was no genetic theory in his time. Then again, there’s no credible or superior alternative to the theory of evolution, and it will likely be improved upon and explicated technically insofar as technology and scientific imagination allows. Feminists, especially, are rightfully wary of a biologically-justified social patriarchy, especially one that involves oppression and social stasis.