According to what I've read on them, the point was that humans didn't used to take care of their teeth, so they fell out faster, and moved in to replace something that had already rotted away.

Damn our ability to prevent tooth decay!! (jk!)

And yes, in the upper jaw... though, I'm fearing popcorn kernels. I love popcorn... I've had cases with bits stuck back behind where the wisdom teeth are, and I have this feeling it's just going to be that much crazier to deal with now. Can't imagine the difficulty with peas... hmm... maybe perpetual cheesecake is the way to go...