Mental Disorders as Catastrophic Failures of Mating Intelligence

Some animals attract mates by displaying indices of genetic quality known as sexually selected fitness indicators (Andersson, 1994). Peacocks, for example, vibrate their showy tails as peahens hunt for the male with the biggest tail. That’s because his big tail indicates that he has the genes most likely to produce high fitness in her offspring. Similarly, some human mental abilities, such as language, music, dance, art, and humor, may function as fitness indicators-the human equivalents of peacock tails (Miller, 2000). If so, those mental abilities must vary greatly in quality and that variation must include low-fitness, unattractive extremes-the human equivalents of small peacock tails. Why? Because fitness indicators can be used for mate selection only if some beaus have high-quality attractive versions and others don’t; the more a trait varies across individuals, the more it can be used to select the fittest mate.