The most striking genetic divergence between humans and chimps occurs in the Y chromosome

William Tucker:

Basically, the point is that, in crossing the little evolutionary distance that exists between chimps and humans, most of the changes occurred in males. In other words, what differentiates us from our mammalian relatives is changes that have occurred in the male of the species.

Actually, this is not news. Evolutionary anthropologists have long been aware of it. As far back as 1972, Elaine Morgan, a feminist, writing in The Descent of Woman, noted that in fact the role of females hadn't changed much from chimp to human. Mothers nurse and care for their offspring in basically the same way chimps do. In terms of social role, there really isn't much difference between human females and other animals.

What has changed is the role of males. Among chimps, males hang out in groups, form alliances, forage together, and do a lot of bickering over status. They do not participate at all in child rearing. By the time hunting-and-gathering tribes arrive, however, men have been folded into the family. Monogamy predominates and both parents participate in child rearing. The extraordinary innovation is "fatherhood," a role that doesn't really exist elsewhere in nature.

What Makes us Different?

Initial sequence of the chimpanzee genome and comparison with the human genome