Are you suggesting rape doesn't happen among hunter-gatherers?

No, but I am suggesting it's probably not been selected for as a genetic predisposition due to the fitness it supposedly brings. The cost/benefit ratio seems pretty damn bad. Let's assume a man of 25 (great fertility, past the peak risk-of-mortality age on a pure-forager's lifespan curve, presumably able to provide for himself to greater or lesser degree.) Assume he only targets women of peak reproductive age, 25 to 30 years (this is very generous for the rape-as-adaptation argument; in reality rapists are known to target women of any age, from single-digits to senescence), thereby maximizing expected payoff per act.

He loses fitness if:

-He is killed by the victim or her relatives. How likely this is depends entirely on his culture -- some forager band societies are quite pacifistic; others resort quickly to violence and have no real way to regulate its spread. It's a pretty strong risk, though.

-The mother refuses to raise the child. This is unlikely to happen, but in a society with high infant mortality rates and established protocols for socially-legitimate infanticide by abandonment or handing off to a relative for culling (standard practice in societies like these if the baby is more than 48 hours old; otherwise the mother usually does it), it's not socially-costly behavior either.

-Having a reputation as a rapist makes it harder for him to survive. This is a virtual certainty -- cooperative food acquisition, compulsory sharing and an ethic of reciprocity are standard features of societies like these. Cutting someone off from this network of assistance is as good as a death sentence in most cases; it also means he's unlikely to ever get consensual sex, or medical assistance when he's hurt. I can't overstate how bad an outcome this is, and how likely it is to happen -- tribal societies don't keep many secrets!

Meanwhile, he gains fitness if and only if all of the following happen: -The victim is potentially able to concieve on that given day AND -She does (the cumulative on these first two items equals 3 - 5 percent odds of conception for consensual sex), AND -She doesn't then miscarry (true 90 percent of the time), AND -She won't voluntarily let the unwanted baby die (not sure, but estimates for the probability of routine infanticide in paleolithic cultures ranges from 15 percent on the lower end, up to 20 or even 50 percent in some cases). No idea offhand, but it seems a heck of a lot more likely than it would be today in the Western European culture area.

You'd have to get incredibly lucky to have a payoff even once; it's certainly not a viable reproductive strategy, not even a distant also-ran that some minority of the population favors. Human population densities in the EEA simply don't support it.

So the fact that rape is common suggests that it's happening for some other reason than it being an evolutionarily-fixed, advantageous trait.