Free Why is Sex Fun?: the evolution of human sexuality by Jared Mason Diamond Page B

the role of men as protectors. The males of many territorial animal species, such as songbirds, lions, and chimpanzees, spend much time patrolling their territories. Such patrols serve multiple purposes: to detect and expel intruding rival males from adjacent territories; to observe whether adjacent territories are in turn ripe for intrusion; to detect predators that could endanger the male's mate and offspring; and to monitor seasonal changes in abundance of foods and other resources. Similarly, at the same time as human hunters are looking for game, they too are attentive to potential dangers and opportunities for the rest of the tribe. In addition, hunting provides a chance to practice the fighting skills that men employ in defending their tribe against enemies.
    This role of hunting is undoubtedly an important one. Nevertheless, one has to ask what specific dangers the hunters are trying to detect, and whose interests they are thereby trying to advance. While lions and other big carnivores do pose dangers to people in some parts of the world, by far the greatest danger to traditional hunter-gatherer human societies everywhere has been posed by hunters from rival tribes. Men of such societies were involved in intermittent wars, the purpose of which was to kill men of other tribes. Captured women and children of defeated rival tribes were either killed or else spared and acquired as wives and slaves, respectively. At worst, patrolling groups of male hunters could thus be viewed as advancing their own genetic self-interest at the expense of rival groups of men. At best, they could be viewed as protecting their wives and children, but mainly against the dangers pound by other men. Even in the latter case, the harm and the good that adult men bring to the rest of society by their patrolling activities would be nearly equally balanced.
    Thus, all five of my efforts to rescue Ache big-game hunting as a sensible way for men to contribute nobly to the best interests of their wives and children collapsed. Kris-ten Hawkes then reminded me of some painful truths about how an Ache man himself (as opposed to his wife and kids) gets big benefits from his kills besides the food entering his stomach.
    To begin with, among the Ache, as among other peoples, extramarital sex is not uncommon. Dozens of Ache women, asked to name the potential fathers (their sex partners around the time of conception) of 66 of their children, named an average of 2.1 men per child. Among a sample of 28 Ache men, women named good hunters more often than poor hunters as their lovers, and they named good hunters as potential fathers of more children.
    To understand the biological significance of adultery, recall that the facts of reproductive biology discussed in chapter 2 introduce a fundamental asymmetry into the interests of men and women. Having multiple sex partners contributes nothing directly to a woman's reproductive output. Once a woman has been fertilized by one man, having sex with another man cannot lead to another baby for at least nine months, and probably for at least several years under hunter-gatherer conditions of extended lacta-tional amenorrhea. In just a few minutes of adultery, though, an otherwise faithful man can double the number of his own offspring.
    Now compare the reproductive outputs of men pursuing the two different hunting strategies that Hawkes terms the “provider” strategy and the “show-off” strategy. The provider hunts for foods yielding moderately high returns with high predictability, such as palm starch and rats. The show-off hunts for big animals; by scoring only occasional bonanzas amid many more days of empty bags, his mean return is lower. The provider brings home on the average the most food for his wife and kids, although he never acquires enough of a surplus to feed anyone else. The show-off on the average brings less food to his wife and kids but does occasionally have lots of meat to share with