Free The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature by Geoffrey Miller Page A

body, but has indirectly influenced the progressive development of various bodily structures and of certain mental qualities. Courage,
pugnacity, perseverance, strength and size of body, weapons of all kinds, musical organs, both vocal and instrumental, bright colors, stripes, and marks, and ornamental appendages, have all been indirectly gained by the one sex or the other, through the influence of love and jealousy, through the appreciation of the beautiful in sound, color or form, and through the exertion of a choice; and these powers of the mind manifestly depend on the development of the cerebral system.
Modern critics who accuse Darwin of reducing all of nature's beauty to the blind, dumb action of natural selection could not have read this far. Darwin spent decades thinking about aesthetic ornamentation in nature, realizing that natural selection cannot explain most of it, and developing his sexual selection ideas precisely to describe how animal psychology leads to the evolution of animal ornamentation.
Wallace Versus Female Choice
Alfred Wallace was an unlikely critic of Darwin's sexual selection theory. He independently discovered the principle of natural selection while Darwin was still reluctant to publish. He was even more of a hard-core adaptationist than Darwin, constantly emphasizing the power of selection to explain biological structures that seem inexplicable. He was the world's expert on animal coloration, with widely respected theories of camouflage, warning coloration, and mimicry He was more generous than Darwin in attributing high intelligence to "savages." Where Darwin was of the landed gentry and fell into an easy marriage to a rich cousin, the working-class Wallace struggled throughout his early adulthood to secure a position sufficiently reputable that he could attract a wife. One might think that Wallace would have been more sensitive to the importance of sexual competition and female choice in human affairs. One might have expected Wallace to use those insights into human sexuality to appreciate the importance of female choice in shaping animal ornamentation. Yet Wallace was utterly hostile to Darwin's theory of sexual selection through mate choice.
The fallacious criticisms developed by Wallace are worth outlining because they continue to be reinvented even now. Wallace distinguished between ornaments that grow in both sexes, and those that grow only in males. The first he explained as identification badges to help animals recognize which species others belonged to. This species-recognition function continues to be advocated by most biologists today to explain ornaments that show minimal sex differences. On the other hand, Wallace did not consider male ornaments to be proper adaptations that evolved for some real purpose. Instead, he suggested that they were unselected side-effects of an exuberant animal physiology that has a naturally predilection for bright colors and loud songs unless inhibited by the sensible restraint of natural selection.
Take a random animal, cut it in half, and you may see some brightly colored internal organs. Wallace pointed out that internal coloration cannot usually result from mate choice because skin is usually opaque. He argued that organs have a natural tendency to assume bright colors just because of their chemistry and physiology. Ordinarily, natural selection favors camouflage on the outside, so animals often look dull and drab.
Wallace then made an additional claim: the more active an organ, the more colorful it tends to be. He observed that males are generally more vigorous, and, confusing correlation with causation, he proposed that this explains why males are brighter. Male ornamentation for Wallace was the natural physiological outcome of inherently greater male health and vigor. In his 1889 book Darwinism, he argued, "The enormously lengthened plumes of the birds of paradise and the peacock ... have been developed
to so great an extent [because] there is a