Evolutionary Psychology

Evolutionary psychological accounts of aggression use principles of evolution to understand both the roots and the contemporary patterns of human aggression. For example, in his book The Most Dangerous Animal: Human Nature and the Origins of War, David Livingstone Smith (2007) emphasizes that human warfare originated not only to obtain valuable resources but also to attract mates and forge intragroup bonds. Smith argues that although our long-ago ancestors put themselves at risk when they engaged in fighting and warfare, they also increased their chances of attracting mates and achieving status in a group. Therefore, the individuals who could and would fight had greater chances for reproductive success, and they would pass down these tendencies to their offspring, who would tend to do the same, and so on. The greater reproductive success of warriors over pacifists would result in the tendencies toward aggression and war to evolve to become part of human nature.

Evolution should have favored the inhibition of aggression against those who are genetically related to us. Consistent with that hypothesis, Martin Daly and Margo Wilson report that birth parents are much less likely to abuse or murder their own offspring than stepparents are to harm stepchildren. In two samples studied, preschool children living with a stepparent or foster parent were 70 to 100 times more likely to be fatally abused than were children living with both biological parents.