Steven Pinker -- How the Mind Works - Hampshire High Italian ...

514 J HOW THE MIND WORKSconsequences are by no means minor. In a classic experiment, the socialpsychologist Muzafer Sherif carefully selected a group of well-adjusted,middle-class American boys for a summer camp, and randomly dividedthem into two groups which then competed in sports and skits. Withindays the groups were brutalizing and raiding each other with sticks, bats,and rocks in socks, forcing the experimenters to intervene for the boys'safety.The enigma of war is why people volunteer for an activity that has anexcellent chance of getting them killed. How could a desire to play Russianroulette have evolved? Tooby and Cosmides explain it by the fact thatnatural selection favors traits that increase fitness on average. Every genecontributing to a trait is embodied in many individuals in many generations,so if one individual with the gene dies childless, the success ofmany others with the gene can make up for it. Imagine a game of Russianroulette where if you don't get killed you have one more offspring. Agene for joining in the game could be selected, because five-sixths of thetime it would leave an extra copy in the gene pool and one-sixth of thetime it would leave none. On average, that yields .83 more copies thanstaying out of the game. Joining a coalition of five other men that is certainto capture five women but suffer one fatality is in effect the samechoice. The key idea is that the coalition acting together can gain a benefitthat its members acting alone cannot, and that spoils are distributedaccording to the risks undertaken. (There are several complications, butthey do not change the point.)In fact, if the spoils are certain and divided up fairly, the level ofdanger doesn't matter. Say your coalition has eleven members and canambush an enemy coalition of five, taking their women. If one memberof your coalition is likely to be killed, you have a ten-in-eleven chanceof surviving, which would entitle you to a one-in-two chance (five captivewomen, ten men) of gaining a wife, an expected gain of .45 wives(averaged over many situations with these payoffs). If two memberswill be killed, you have a smaller chance of surviving (nine in eleven),but if you do survive you have a larger chance of gaining a wife, sinceyour dead allies won't be taking theirs. The average gain (9/11 x 5/9) isthe same, .45 wives. Even if six members are likely to be killed, so thatyour survival odds fall to less than even (five in eleven), the spoils aredivided fewer ways (five women among five victors), so if you $urviveyou are guaranteed a wife, for an expected gain, once again, of .45wives.