Large groups also allow the bonobos to develop strong female-to-female alliances so that they can defend themselves against males when solicitations of sex become violent.

In addition, female bonobos conceal their ovulation so that males are less likely to fight over them.

"Chimpanzee females reveal their ovulation, and the result is mayhem," Wrangham said. Male chimpanzees know when females are fertile and often become violent.

And although bonobos, like chimpanzees, eat meat, they are almost never observed to hunt.

Although Wrangham declined to draw conclusions about humans based on his research among the great apes, he said he believes the similarities are important.

Wrangham suggested that there might be parallels between human war and violence against women and chimpanzee lethal raiding and rape.

"The deep lesson here is that the similarities we see in apes force us to see similarities in ourselves," he said

"Like chimps," said Wrangham, "we are ourselves a chimeric species. You can look in the face of a chimp and see both hostility and sympathy."

Yet like bonobos, human beings live in large groups and the females conceal ovulation.

"I don't want to suggest that we are bonobos any more than we are chimps," Wrangham said.

"It is simply that [looking at these apes] starts to give you a sense of how violence could possibly relate to chance in evolution," Wrangham continued.

"Patterns of violence come from deep within our brains, and we need to be aware of that."

According to David Pilbeam, Ford professor of the social sciences and the dean for undergraduate education, Wrangham's book is "well done and full of insights and provocative argument."

"I would like to see it form the basis of a rational, civil discussion on the interaction of 'biology' and 'culture,'" Pilbeam said.

Demonic Males: Apes and the Origins of Human Violence was co-authored by Dale Peterson.