PS, I just learned something in my Anthropology class that has really stuck with me. I say the answer is EVOLUTION. I recently emailed this to a friend, so I will just paste it here again---it's takes too long to write it out again. Tell me what you think!
So in my anthropology class i learned something so intriguing, I haven't been able to stop thinking about it. It's about chimps and bonobos. They share a common ancestor. But then along came an extended drought that affected a portion of the population. This forced the affected population to start climbing trees to get food. The other group could continue foraging on the ground. So here are the social differences that led to: The tree eating females grew weaker. They often were caring for infants, and they were weaker than the males, so they couldn't climb the trees as fast to get food. So the males became dominant. Also because this type of foraging tends to be solitary, the females did not form strong alliances and bonds with other females. The ground eating females had no such competition. They could forage with other females and form strong bonds and alliances with them. The society remained much more equal, and they had nothing to fear from the males. The results: The tree eaters evolved into chimpanzees. They are violent and fight other groups of chimps. They are violently abusive to females and commit infanticide against offspring that are not their own. The females have not learned to rely one another, so they are on their own. They will try to mate with every male in their group to reduce the likelihood that the males will kill their offspring. If all the males think the kid could be theirs, they are safer. The ground eaters evolved into bonobos and live a peaceful nonviolent life. The females stand together, so the offspring are not in danger. They have sex ALL THE TIME. Female/Male, Female/Female, Male/Male. It simply doesn't matter. They are too busy making love to make war. Guess which species human DNA is closer too? Yeah---the chimps. Freaking Drought!