I don't think we can know much about how social norms and rape played out in the early environment.

We can make some inferences from mobile foragers who've maintained some cultural distance from the outside world, though -- they're not a perfect substitute, but they tell us something about patterns of human behavior and existence in the absence of other economic or ecological resource bases.

It's certainly a whole lot more likely to be, at minimum not entirely off-target, than you'll be semi-consciously conflating "hunter-gatherer" as a synonym for "primitive", assuming that all societies without industrialization or intensive agriculture of the type one recognizes are in that category, failing to account for the spread of of particular value-systems and norms that have widely impacted societies around the world, and hyper-focusing on chimps to the exclusion of other primates as analogues for our own evolutionary history (which is what I'm seeing and responding to here).