Expanding on the ideas of Darwin, Fisher, Cronin, and others, in The Mating Mind, Geoffrey Miller proposes that art, language, music, religion, and other human qualities that are difficult to understand as products of natural selection have arisen by the more rapid process of sexual selection through mate choice.
2. The central idea is simply this: selection of a particular member of the opposite sex for the purpose of reproduction can, and sometimes does, produce a positive, runaway feedback process resulting in extravagant traits out of all proportion to what is required for mere survival, even for mere reproduction. In this way a species develops characteristics unlike those of its phyletic neighbors. In addition to the ubiquitously cited peacock tails, examples include the elaborate constructions of bower birds, deer antlers, elongated giraffe necks, colorful bird plumage, exaggerated fish tails, and human language.
3. Quoting Miller, "If hominid females happened to develop a sexual preference for creative intelligence, then males with more creative intelligence would attract more sexual partners and would produce more offspring. Those offspring would inherit both the taste for clever courtship and the capacity for producing it. Over many generations, average creative intelligence in the lineage would increase rapidly, perhaps explaining why brain size tripled in just two million years."
4. Sexual selection is unlike the slow and plodding natural selection process we have all come to know and love, but find hard to defend when faced with certain puzzles like how could eyes and feathers evolve when they are good for sight and flight only when the process is complete, or why is the fossil record so stingy about intermediate types? One possible answer for those who understand the power of sexual selection is that traits odd by survival standards can develop at breakneck speed, evolutionarily speaking, when caught up in the cycle of sexual preference. However a particular proclivity may have originated, mate choices that are dictated by a preference will spawn offspring with both the trait and the preference.
5. A central concept is that of the "fitness indicator," the idea that cumbersome ornamentation advertises good genes, genes, for example, that resist invasion by parasites. Here, Miller leans heavily on Zahavi's (1975) handicap principle according to which display of a costly trait signals fitness so good as to be able to withstand the impediment. Miller's analogy is that the man who gives a woman a very expensive jewel is communicating to her that there must be a lot of wealth behind it if he can afford so extreme a financial outlay. As Fisher also argued, whatever may be its value in survival terms, attractiveness increases the probability of selection and therefore is reproductively valuable. If males develop the trait the daughters develop the preference and vice versa, a point also stressed by Helena Cronin in The Ant and the Peacock (1992).
6. Permeating the text is fulfillment of Miller's announced intention to bring evolutionary theorizing down to ordinary life conditions. Sexual selection explains why people prefer fiction to non-fiction, religious myth to scientific evidence, and political correctness to intellectual coherence. In addition, selection by both sexes produced certain sex-related traits. Female selection led to male human beards, large penises, and formidable upper-body muscles. Male selection produced bulging female breasts, rounded buttocks, full lips, and neotenous facial features. Furthermore, sexual attractants for both sexes include morality, kindness, aesthetics, and body ornamentation. Kohn and Mithen (1999) have proposed that the handaxes found in multiple digs across three continents might have been produced as sexual ornaments.
7. There are problems. Miller painstakingly delineates many of them. The price of sexually selected ornamentation can be worse than merely costly. Natural selection can put a stop to a process that goes too far. The products of runaway sexual selection may hinder adaptation to environmental demands as when heightened colors attract predators or excessive testosterone reduces resistance to infection. A long tail feather can obstruct the process of obtaining food or beak size can increase to the point that new food gathering strategies must be devised. Although Miller says little about runaway violence, preference for aggressive traits can have dire consequences.
8. Alternate explanations for human culture see it as a byproduct or side effect of intelligence adapted for survival by natural selection. William Calvin (2002) proposes that extreme environmental conditions brought on by rapid climactic swings gave impetus to complex intelligence because when grass became the only plant available after rapid cooling of the planet had eliminated vegetation directly digestible by humans, successful hunting of large grazing animals required innovation and cooperation.
9. Although Miller may sometimes stray too far into speculation, it can be comforting to think that such human attributes as "sympathy, kindness, sexual fidelity, moral leadership, magnanimity, romantic gift-giving, and sportsmanship" are grounded in our biological history. It suggests permanence beyond cultural training. In this vein, Miller tries his best to reassure us that biological heritage need not deprive us of mysticism or romance and that while art may have arisen through sexual selection, so may have aesthetic sensitivity, both of which are here to stay and enjoy.
10. Although by Darwin and Fisher, as well as many others, it is the female who does the lion's share of the choosing, mutual choice is evident and even mating imposed by others is selective for traits deemed attractive to the group thereby increasing both the trait and the preference in future generations.
11. A lesson that the history of science repeatedly teaches is how prejudice and ideology can obstruct progress. The reason for sexual selection having been ignored for so many decades was, in Miller's view, and he is by no means alone in this, that the emphasis on female mate choice didn't sit well in the patriarchal mind. It has been noted that women scientists are making scientific progress today as are men who no longer hold views of female inferiority. Today, ideas are accepted that were formerly rejected out of hand.
12. Miller admits that as good as sexual selection theory is in handling some aspects of human nature, it is largely confined to fancy "ornamentation" and traits that otherwise defy survival of the fittest explanations. With humility, he claims only to have provided a "snap-shot of a provisional theory under construction." Indeed, the text is replete with "mays," "mights," and "maybes." Furthermore, straightforward prediction on the basis of sexual selection would expect sex differences in intelligence that have not been found. Still, there exists what Miller considers evidence in favour of his conjectures, notably the obvious and ubiquitous human mate preference sex differences such as have been documented by Buss (1989) and other evolutionary psychologists.
13. Miller's critics tend to be critics of evolutionary psychology generally, not of Miller in particular. For example, Stephen Rose (2000) finds evolutionary psychologists "trapped within an almost religious longing for simple-minded explanations" thereby failing to recognize "the complexity of the world we live in, and the necessary autonomy of the many disciplines trying to understand and explain it." In contrast, Deborah Zion (2000) found The Mating Mind "thoughtful, witty and vividly written" although perhaps somewhat "mindlessly optimistic." Is it really a "groundbreaking book that will transform our understanding of our species"? Perhaps. Easy to read, it brings an important message to where it might otherwise never go.
14. But I was not always convinced by his conjectures. The book's length and repetitions sometimes bored me and I was frustrated by his omission of any extended treatment of sexually selected aggression or other negative behaviors. Finally, more personally, although Miller used the phrase "in love" at least a dozen times, I'd like to have been given a definition and some consideration of its possible adaptation through sexual selection.
Buss, David M. (1989). Sex differences in human mate selection: Evolutionary hypotheses tested in 37 cultures. Behavioral and Brain Sciences 12 (1), 1-49.
Calvin, William (2002). A Brain for All Seasons: Human Evolution and Abrupt Climate Change (University of Chicago Press).
Cronin, Helena (1991). The Ant and the Peacock: Altruism and sexual selection from Darwin to today. (Cambridge University Press).
Darwin, Charles (1871). The Descent of Man (John Murray, London).
Fisher, R. A. (1930). The Genetical Theory of Natural Selection (Clarendon Press, Oxford).
Kohn, Marek and Mithen, Steven (1999). Handaxes: Products of Sexual Selection? (Antiquity 73, 1999: 518-26).
Miller, G. F. (2000) The mating mind: How sexual choice shaped the evolution of human nature. (New York: Anchor Books).
Miller,G.F. (2001) Precis of: The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature. PSYCOLOQUY 12(008) http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?12.008
Rose, Hilary and Stephen (Eds.) (2000). Alas, Poor Darwin: Arguments against evolutionary psychology. (Cape).
Zahavi, Amotz (1975). Mate Selection: A Selection for a handicap. Journal of Theoretical Biology, 53, 205-214.
Zion, Deborah (2000). "Why brainy is sexy." (The Age Company Ltd.)