@WandererUber @Kirino @WashedOutGundamPilot @moomin >What's "fresh" about different?
Potential to fix a problem. Things like repeating alleles or a less than favorable standard recessive trait can be potentially buried.

>And you would still have natural selection in a small population. So what makes it necessary to "trade" genes with the next tribe over, who has THE SAME PROBLEM?
They share the same collective constraint of a limited genetic pool, but it could manifest on a different area than yours (e.g. different problem trait). Natural selection is actually why this works, because if they bring nothing good to table, it doesn't have to stick.