"Wild chimps reveal the natural contexts of territoriality, war, male
cooperation, solidarity and sharing, nepotism, sexism, xenophobia,
infanticide, murder, cannibalism, polygyny, and mating competition
between kin groups of males -- behaviors that have evolved through
sexual selection. Also significant is the fact that none of these apes
learned these violent behaviors by watching TV or by being victims of
socioeconomic handicaps -- poor schools, broken homes, bad fathers,
illegal drugs, easy weapons, or any other sociological condition. Nor
were these apes spurred to war by any political, religious, or
economic ideology or by the rhetoric of an insane demagogue. They also
were not seeking an 'identity' or buckling under peer pressure.
Instead, they were obeying instincts, coded in the male psyche,
dictating that they must win against other males."


THE DARK SIDE OF MAN: Tracing the Origins of Male Violence,
by Michael P. Ghiglieri; Perseus, 1999; p. 176