Are Aggressive Sisters an American Cultural Phenomenon? |
I recently wrote about a surprising finding among American participants: Contrary to all the data on violent crime, playground aggression, and other measures of aggressive behavior, sisters are every bit as likely to hit, kick, or yell at their siblings as are brothers. The general pattern, and the exceptions, were presumed to have something to do with evolved influences on human behavior. Aggression outside the family has to do with what evolutionary biologists call differential parental investment (females across a wide range of species generally contribute more of their physiological resources to the fetus and infant), which leads to relatively higher female selectivity in choosing mates, and thus contributes to sexual selection (males competing among themselves to be chosen, often by intrasexual aggression). Aggression inside the family is, according to evolutionary biologists, a different game, in which both sexes are competing for the same resources.
But the finding of high aggression among sisters might instead have been explained........