Okay, okay, Faldwellian politics aside. Let's work this one out.

You have a house cat and you have a lion....They are very similar because they are in the same 'family'. They are in the same 'family' because________.(fill in the blank)

You have a chimpanzee and you have a man. Their chromosomal compatibility is similar enough to actually cross-breed. (at least to the point of fertilizing the egg-more than likely all the way, but I'm not will to go all the way with a chimp just yet).
This is true because_______________.