We have evidence that chimps rape

taking the way chimpanzees live now as an very broad approximation of how our great great great ancestors lived

We do share a common ancestor with chimps, yes. From this common ancestor is descended both chimps and bonobos.

Given the existence of bonobos, I do not see why chimp-rape is particularly relevant to the question of whether or not rape is adaptive in humans. That is, given the existence of bonobos, it seems uncertain whether or not the common ancestor of chimps and humans (who is also the common ancestor of humans and bonobos) was, how to put this, a rape ape.