T-Rex: Let us assume that everyone alive today has two biological parents, a mother and a father. I will call this the "No Cloned Chicks" hypothesis!
T-Rex: And let us further assume that everyone's parents had a biological mother and father too!
T-Rex: This seems pretty reasonable. But it can't possibly be the case! If you take me, I've got two parents. My parents have two parents themselves, so this means that three generations ago, four people are needed to eventually produce me. Another generation back, we're eight people, and five generations ago gives me sixteen ancestors!
Utahraptor: And if you go back a 1500 years or so, say, fifty-five generations?
T-Rex: That's exactly the problem!
T-Rex: At fifty-five generations I've got over TEN QUADRILLION grandparents all running around at the same time! Man! There's NO WAY there was room for that.
Utahraptor: Ah, but you're assuming everyone's sexing up a total genetic stranger. If you sex up a relative, any child produced will have fewer grandparents!
T-Rex: ...Huh! So the fact that there weren't ten quadrillion people 1500 years ago SCIENTIFICALLY PROVES that some of my ancestors liked sexing it up with their cousins!!
T-Rex: ...
T-Rex: ...Huh.
