quite varied in their testosterone levels, and presumably they always have been. Even those who are low in testosterone manage to reproduce quite well, and low-testosterone men appear in every generation. What is missing from the view that testosterone brings success is the fact that high testosterone also carries a heavy cost.
|
The problem is that individuals with extremely high levels of testosterone are likely to die before they have offspring. Studies with animals illustrate this. Male birds injected with testosterone sing more, patrol larger areas, have more fights, and are less likely to live out the year. Those that do live end up with more injuries. 17 When male lizards are given extra testosterone, they fight more, move around more, and can be seen more easily in the wild, all of which makes them less likely to survive. 18 Evolution maintains a delicate balance between producing enough testosterone to compete successfully and producing so much that one's own survival is at risk. Among many animals, castrated males live longer. This is true of sheep, cats, rats, and moths. It is also true of men. 19 Even normal levels of testosterone put men at risk, though most men would reject castration as a way of gaining a long life.
|
Just as high levels of testosterone make men as a group more combative than women, men with more testosterone are more combative than men with less testosterone. Higher-testosterone men have more problems in relationships with their mates. Higher-testosterone men are less reliable as mates and fathers, and men who ignore their wives and children will have fewer viable offspring. Females seem to recognize both the good and the bad aspects of masculinity. In general, they find men attractive who are high in testosterone but not too high, men who have a good build but are not muscle bound. Despite the effort men put into developing their muscles, most women do not find highly muscular men especially attractive. 20 Perhaps male bodybuilders are more interested in competing with other men than in attracting women. The preferences of females, along with the hazards of high testosterone levels, explain why the males of many species, including male vervet monkeys and men, do not have higher levels of testosterone with each new generation. Vervet monkeys are good-natured ground dwellers that live on the African savanna. The females take part in selecting leaders from among the males in the troop. The females, who do not like overly excitable or combative males, promote calm and peaceful leaders. 21
|
|