The Pygmies of Central Africa and the Arapesh of New Guinea live in peace and harmony, while European history consists of one war after the other.Formerly peace-loving, the Iroquois became a fierce and aggressive Native American tribe in the seventeenth century. These examples illustrate thata. in humans, innate behavioral patterns—including aggression—are infinitely malleable and modifiable.b. frustration often contributes to aggression in otherwise peaceable societies.c. there are strong regional differences in the endorsement of aggression as a solution to social problems.d. humans, lacking inhibitory mechanisms, must rely on cultural norms to curb aggression.