Well, one of the things you will have to examine is how the heck any human male would get close enough to a gorilla or chimpanzee female to crossbreed without being killed first. These primates are intrinsically much more powerful than humans… even more powerful than human males.
Then there is the conflicting behavior patterns. Unlike what can be found in human mating, it is virtually impossible for a non-human primate female to be compelled to mate. While theoretically non-human primate males have the strength, it would require a very different learned approach to females. In the wilds, female primates just sit down and that’s the end of the day for the male.
There’s no extended threats, or negotiations to prolong the discussions. And there is no way to communicate that “if she does or doesn’t do something, drastic measures are inevitable”.
So let’s anticipate a possible refutation: male human with female non-human. She sits down, and he starts to explain what she has to do if she knows what is in her best interests. What language would the male human use that the female would understand?
And if a rape is attempted human style, it is well within the female chimp or gorilla’s behavioral catalog for violence to kill the human right there.
While it is feasible, I suppose, in some sick or deluded way, to imagine that humans could capture female primates and cage them, I think you will find plenty of anecdotal evidence that there was no systematic way for humans to safely enter a cage with a primate of any size. Until the advent of the tranquilizer gun, the idea of surviving “a date” with a female gorilla seems most unlikely.
Let’s reverse the question: Male gorilla’s capturing female humans… and then what? There would be no grim recital of pre-rape threats… Because non-human primates are not the best conversationalists.
Female resistance would be answered with a simple primate response of breaking an arm or smashing a skull. But in a population where pheromones are the principle methods of foreplay, why would a non-human primate find humans at all interesting? From their viewpoint, humans are just soooooooo hairless… gruesomely so! And without the right pheromone, could a non-human primate male even discover enough arousal as to make any of this plausible?
And finally, @r_speir, there is the genetic biochemistry of human and non-human gametes. If our chromosomes were compatible 6000 years ago … they would be compatible still today! In fact, they should be more so, if the current generations reflect any past cross-breeding. A few petri dishes could quickly confirm what we have all be explaining to you: at the biochemical level, not just all the other levels, you would discover that it just couldn’t happen.