Sexual choice is mediated by the senses. We cannot use telepathy to pick sexual partners. We have to rely on the evidence of our eyes, ears, noses, tongues, and skin. Since the senses are the first filter for sexual choice, sexual ornaments evolved to play upon the senses. Biologists have started to analyze sexual ornaments as sound and light shows designed for sensory appeal.
Yet sexual choice also runs deeper than the senses. It depends on memory, anticipation, judgment, decision-making, and pleasure. Psychological preferences go beyond sensory preferences. For most species these more sophisticated psychological preferences probably do not matter very much. As far as we know, their sexual ornamentation has no way of activating ideas, concepts, narratives, or philosophies in the minds of other members of their species. Stimulating the senses is about as deep as they can go, because they have no communication system capable of conveying rich ideas. But after our ancestors evolved communication systems such as language, art, and music, psychological preferences may have become crucial in sexual selection.
Those preferences could have gone far beyond the eye's love of bright color and the ear's response to rhythm. They could have included mental quirks that make us prefer novelty to boredom, grace to clumsiness, knowledge to ignorance, logic to inconsistency, or kindness to meanness. If these quirks influenced the sexual choices that shaped the mind's evolution, then the mind could be viewed as an entertainment system that appeals to the psychological preferences of other minds. Just as some books become best-sellers for their contents rather than their covers, our ancestors attracted mates by displaying interesting minds, not just shapely bodies and resonant voices. Our minds may have evolved as sexual ornaments, but ornamentation is not limited to a superficial appeal to the senses. As far as sexual selection is concerned, creativity can be ornamental. Consciousness itself may be ornamental.
As we saw in the previous chapter, many sexual ornaments work as fitness indicators. But almost any trait that varies conspicuously and costs a lot can work as a fitness indicator. One important question is, which fitness indicators will evolve, out of the huge number possible? The runaway process cannot help us here, because it is arbitrary about what kinds of trait it favors. Sensory preferences might be more help in understanding which indicators evolve, because, by definition, they prefer some styles of ornamentation over others. This chapter reviews how biologists have been thinking about sensory preferences, and then generalizes their ideas to consider how psychological preferences may have influenced sexual selection among our ancestors. We shall also see how fruitful interactions occur between all three sexual selection processes we have been considering—runaway processes, fitness indicators, and, in this chapter, ornaments that appeal to the senses and the mind. When I go on to analyze specific human capacities such as art and creativity, I shall draw on all three of these ideas. They are not only complementary processes in evolution, but they offer complementary perspectives on the human mind.
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