Avatar driver hours and "matechoosing"

[Raiden]

The way most people seem to understand the mate thing, (if this hasn't already been said) is that after a male Na'vi completes all of his training and rites of passage, they are allowed to pick from amongst the clan females.

The thing that has me curious about this has to do with gene pools.....if one clan just kept interbreeding, eventually the gene pool would become too "stagnant" and there would be a huge spike in stillbirths and deformities.

Other animals that live in groups like this have a similar problem, and it is usually solved mainly through the influx of new members of the same species to the "clan".

So, my question is, to solve this problem, which they must know about (even ancient Earth civilizations understood inbreeding was dangerous, I'm making an educated assumption), do the Na'vi occasionally allow males to court/choose females from other clans?

I can't really think of any other way to solve the problem, and mutation is a very very slow process (most humans have 10,000+ mutations occur in their genes each day, but more than 99% of them are harmless, and your body has a vast anti-mutation "toolkit", as well as a myriad of "checkpoints" at which mutations are likely to be detected before they can be translated into cells and cause things like cancer), so would the Na'vi cross-mate individuals into/out of different clans to solve the problem?