Miller/Sexual Selection

Sexual selection

by Geoffrey Miller, University of New Mexico, gfmiller@unm.edu

Evolution is driven not just by the survival of the fittest (natural selection), but by the reproduction of thesexiest (sexual selection). If an animal finds food and avoids predators, but can’t find a mate, the animal is an evolutionary dead-end. Its genes will die out when it dies. This is why sexualselection is so important: it is the evolutionary gateway to genetic immortality. Every one of your ancestors managed not just to survive to adulthood, but also to attract a willing sexual partner. Everyone of your 30,000 genes has passed through thousands of generations of successful courtship, mating, and parenting.

‘Sexual selection’ is another term for reproductive competition – competitionto attract more high-quality mates than one’s sexual rivals, to have more high-quality offspring. Charles Darwin discovered sexual selection, and published a massive book about it in 1871, but sexualselection was usually ignored in biology until the 1970s, and in psychology until the 1990s. Since then, biologists have realized that many traits in animals have been shaped by sexual selection,either as sexual ornaments to attract mates (e.g. the peacock’s tail, the nightingale’s song, the female baboon’s bright red bottom) or as weapons for sexual competition against rivals (e.g. deerantlers, gorilla muscles, big male baboon teeth). Since about 1990, evolutionary psychologists have also realized that many human traits have been shaped by sexual selection. These sexually-selectedtraits include: (1) socially salient physical traits such as female breasts and buttocks, and male beards, upper-body muscles, and penises, (2) person-perception abilities to judge the attractiveness ofpotential mates, including their beauty, kindness, intelligence, and status, (3) self-presentation abilities (ways of showing off in courtship) such as language, art, music, and humor, and (4) social...