"Have you ever seen the gentic bottle neck and defect results from even a small population of say 10 or 20 individual interbreeding? Eventually infertility sets in and the population dies off. This is true of most higher animals: tigers, humans, apes, etc."
I'm not the one saying it; it's these scientists.
The scientists are talking of an initial population of 1500 breeding adults (around 3,000 kids). That's not a genetic bottleneck. 2 would be a massive genetic bottleneck and a sure sign of extinction. Oh, and on the Biblical side of things, if you take the literal interpretation, who did Caine marry? God gave him a woman, from where? Or was she also created?