The Better Angels of Our Nature: Why Vio - By Steven Pinker Page 0,315

pituitary gland, which can secrete a hormone that tells the testes or the adrenal glands to produce more testosterone.

Though testosterone is often identified in the popular imagination as the cause of male pugnacity—“the substance that drives men to behave with quintessential guyness, to posture, push, yelp, belch, punch and play air-guitar,” as the journalist Natalie Angier put it—biologists have been nervous about blaming it for male aggression itself.118 Raising testosterone undoubtedly makes most birds and mammals more obstreperous, and lowering it makes them less so, as the owner of any neutered dog or cat is aware. But in humans the effects are less easily measured, for a number of boring biochemical reasons, and they are less directly tied to aggression, for an interesting psychological reason.

Testosterone, according to scientists’ best guess, does not make men more aggressive across the board, but prepares them for a challenge of dominance.119 In chimpanzees, testosterone goes up in the presence of a sexually receptive female, and it is correlated with the male’s dominance rank, which in turn is correlated with his aggressiveness. In men, testosterone levels rise in the presence of an attractive female and in anticipation of competition with other men, such as in sports. Once a match has begun, testosterone rises even more, and when the match has been decided, testosterone continues to rise in the winner but not in the loser. Men who have higher levels of testosterone play more aggressively, have angrier faces during competition, smile less often, and have firmer handshakes. In experiments they are more likely to lock their gaze onto an angry face, and to perceive a neutral face as angry. It’s not just fun and games that pump up the hormone: recall that the southern men who were insulted in Richard Nisbett’s experiment on the psychology of honor responded with a rise in testosterone, and that they looked angrier, shook hands more firmly, and walked out of the lab with more of a swagger. At the tail end of the belligerence spectrum, prisoners with higher levels of testosterone have been found to commit more acts of violence.

Testosterone rises in adolescence and young adulthood, and declines in middle age. It also declines when men get married, have children, and spend time with their children. The hormone, then, is an internal regulator of the fundamental tradeoff between parenting effort and mating effort, where mating effort consists both in wooing the opposite sex and in fending off rivals of the same sex.120 Testosterone may be the knob that turns men into dads or cads.

The rise and fall of testosterone over the life span correlates, more or less, with the rise and fall of male pugnacity. Incidentally, the first law of violence—it’s something that young men do—is easier to document than to explain. Though it’s clear why men should have evolved to be more violent than women, it’s not so clear why young men should be more violent than old men. After all, young men have more years ahead of them, so when they take up a violent challenge, they are gambling with a greater proportion of their unlived lives. On mathematical grounds one might expect the opposite: that as men’s days are numbered, they can afford to become increasingly reckless, and a really old man might go on one last spree of rape and murder until a SWAT team cuts him down.121 One reason this does not happen is that men always have the option of investing in their children, grandchildren, nieces, and nephews, so older men, who are physically weaker but socially and economically stronger, have more to gain in providing for and protecting their families than in siring more offspring.122 The other is that dominance in humans is a matter of reputation, which can be self-sustaining with a long payout. Everyone loves a winner, and nothing succeeds like success. So it is in the earliest rounds of competition that the reputational stakes are highest.

Testosterone, then, prepares men (and to a lesser extent women) for contests of dominance. It doesn’t cause violence directly, because many kinds of violence have nothing to do with dominance, and because many contests of dominance are settled by displays and brinkmanship rather than violence itself. But to the extent that the problem of violence is a problem of young, unmarried, lawless men competing for dominance, whether directly or on behalf of a leader, then violence really is a problem of there being too much testosterone in the world.

The socially constructed nature of dominance can