Wow, what if we aren't chimps at all then? What if we were originally some sort of super-intelligent velociraptor types who got a bunch of uh, retroviruses from chimps, by you know Doin It with them, thinking it would be Safe ("No eggs in this one," said ZZaxx, slapping her hairy thigh)and so now 50 million years later, we have a rule about that stuff but it's way too late, we're chimps, wages of sin and all that.
Just a theory