What is the westermarck effect?

How do small isolated tribes deal with the westermarck effect?(would like anthropologists to also chime in.)?

• So the westermarck effect(Reverse sexual imprinting) stops kids who grew up real close together from being sexually attracted to each other as adults. But as I mentally visualize a small isolated tribe, with a few huts. The adult males are hunting or doing something, the women are gathering nuts and fruits, and the kids are practically 24-7 near each other playing together. There's no internet, no tv, nothing to do but physical games. So what happens here, how do these people cope with this? Do they abandon the tribe in search of a mate? Do they mate with each other but find it repulsive? If not why not? I mean every kid in the tribe would have grown up closely with every other kid, as adults they should find sexual attraction to each other repulsive(ie feel like brothers & sisters do, even if biologically unrelated if they grew up from early childhood together.), but they must obligatorily mate to generate the next generation and inspire the next generation to do the same.

• Answer:

  most child hood marriages that i have observed in out world survive much better than when two total strangers meet and marry!!! i do not for see any problems!!!