I never said crackpots are guaranteed to be visionaries, though I'm sure it made a convenient strawman for you to argue against. My only point was that you can't be certain either way a priori, to be sure you must actually investigate it (and history tells us even then that's not always going to guarantee certainty).
The depth of investigation should be proportional to the probability of correctness, weighted by the cost of being wrong. Crackpots are called such because the probability of correctness is very low.
Given all the evidence, I consider the MFAP origin hypothesis to be significantly less likely than the primate evolution theory. Extraordinary claims require extraordinary evidence.
to play devil's advocate: consider the extreme absurdity of einstein's theory of relativity, the theory that time may speed up or slow down depending on your velocity.
