I think I remember (???) that even if a small population of humans survived a major catastrophe (i think like 10 people) that 80-90% of the genetic diversity can still be maintained.
We still mutate, and a smaller breeding population has occured many, many times throughout humanities history (due to availability of different tribes within transportation means). That's how you end up with the different developments between some of the races. Mutation sticks, and gets passed around/down like a STD.
Situation like this though (if we applied what we know about modern day genetic diversity) would mean that each woman should have a child by each man. At least half-siblings mating is better than full-blood.
Just sayin.
