*I think this is actually somewhat well validated, under the name of "instinct," and humans appear to have lots of instincts.

Instincts wouldn't be a case of a priori knowledge, I think just because they couldn't be considered a case of knowledge. But at any rate, 'a priori' doesn't mean 'innate', or even 'entirely independent of experience'. A priori knowledge is knowledge the truth of which does not refer to any particular experience or set of experiences. This doesn't imply anything about whether or not it's underived or anything like that: most people who take a priori knowledge to be a thing would consider a mathematical proof a case of a priori justification, and those are undoubtedly derived by some particular person at some particular time using some particular means. (I'm not endorsing the possibility of a priori knowledge, just trying to clarify the idea).