Many occult texts claim that the monkeys of today are a result of back crossing human DNA into monkey species long, long ago; and that they have been in regression ever since, turning less human with time.
https://en.wikipedia.org/wiki/Humanzee
So getting human DNA back into apes doesn't seem possible.
And that's not even mentioning the even remoter chance that the offspring is viable and can reproduce.
Is it really that difficult to imagine? There are all sorts of traces and stories about more advanced civilizations before ours, and more advanced beings than us. As of talking monkeys, people with bird heads and feathers and so on.
I'm with Socrates, I don't know anything for sure about this world. What I do know is that the pieces we've been handed don't match up with my experience.