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

Bad assumption. We're genetically equidistant from chimps and bonobos, who are pretty nearly opposite in their social and sexual behavior.

Did that common ancestor favor one strategy, or the other? Or neither one, or a mix of the two? Is the chimp model an adaptation subsequent to that divergence? Is the bonobo model one? Are both?