How do small closed-off communities maintain genetic diversity?

Answer 1

they believe that they should they are forced to because if they don't they as a group will parish

Answer 2

Although there are a few populations that have had some real problems with inbred undesirable traits, more commonly people around the world have institutionalized out-breeding when it was possible . For example, the Tuareg nomads of the Sahara desert hold festivals for young people to find mates. They may travel many hundreds of miles for this purpose. Where I live (N. California), in pre-settlement times the four local tribes spoke four distinctly different languages, yet marriage between the groups was encouraged. Young people met at the shared salmon dam. People seem to have always known to do the right thing, even if they didn't know the reasons why. I've wondered over this myself and thought that yet undiscovered pheromones may have something to do with it.

Answer 3

outsiders ( if you think about it it is pretty simple just a new infusion of genes every 2nd or 3rd generation is enough - i can't think of any community that doesn't import people every 40 - 60 years )

the only communities that are truly isolated are jungle and island tribes and they all have traditions of exchanging people with neighboring tribes ( or they no longer exist ! )

Answer 4

if they dont, its eventual extinction, in the mean time there are some really odd character traits that manifest themselves, such as blindness loss of skin pigmentation etc whether its plant , animal or any other it remains pretty much consistant to the end

Answer 5

They don't. That's why you get a whole island full of deaf people, or royal families with queer habits and horsefaces.