LogFAQs > #927648476

Genisis 5:4. The days of Adam after he fathered Seth were 800 years; and he had other sons and daughters.

Cain and all of Adam's sons likely married their own sisters or something close to it. There is also the mention of divine beings also mating with man pre-flood era but this is not likely what you were referring to. It is important to note that, even from an entirely atheistic viewpoint, all humans have a 'most recent common ancestor that isn't too long ago species-wise. Simply put, the number of ancestors needed for even one person to not be related to one other person is simply staggering and it doubles with each generation. I forget the exact year but your ancestory tree would have more humans than ever existed sometime around 1,000 A.D. (or was it B.C.?) and that's just one person. So all humans are at least slightly inbred or else there'd be no way to have enough ancestors for you to exist.
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