this concept also pokes holes in the adam and eve story. 2 humans could not produce the genetic variation required to sustain humans today. most offspring would become too far inbred and die within a few generations.
Remember that Adam and Eve were created perfect, and thus it is difficult to say what would be the result of such inbreeding. One would think that at the very least there were no recessive abnormailites to worry about.
I think the Noah situation is much more important for this point. Noah and his kin were not perfect...
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