Okay. So I read that the north sentilese tribe numbers about 50-100. Amongst them and other uncontacted tribes, I don’t believe they have major genetic issues from inbreeding, how is this possible? Or am I mistaken and they have major inbreeding health issues?
One thing to consider is that for an isolated population living entirely off the land, then many of the physical abnormalities resulting from inbreeding would in theory work themselves out. Kids born with misshapen faces or malformed limbs for example very might not live to adulthood and even if they did, they would be less able to reproduce themselves. It’s one thing when your child is heir to the throne and you are the king, then you can tell your son’s sister, niece, aunt, cousin, whatever “no you ARE marrying him, and you ARE having kids!”
For internal illnesses such as hemophilia and schizophrenia, those very well might affect greater percentages of the population. But without being able to do more in depth studies, it’s really impossible to know.
The Sentinelese are part of a larger group of people living on islands in that whole region. They used to trade with other islands but the modern age appears to have cut them off from the larger community. So even though they were just a small group, they were part of a much larger population who they traded and had children with. Will being a small group isolated on an island be bad for their genetics over the course of a few more generations? Possibly. But we have no way to assess that since we are no-contact with them.
Since they’re uncontacted, nobody’s gone and done a health assessment or DNA study, so even if they had issues, we wouldn’t know about it.
However, when we talk about “genetic issues from inbreeding” we’re normally thinking of someone marrying their cousin – a single generation, or maybe just a handful, with a lot of non-inbreeding sprinkled into the family tree. With an uncontacted tribe, we might be talking about generations of literally everyone “marrying” cousins. That’s plenty of time for the most serious defects to appear, and then get “bred out” of the population until those faulty genes disappear.
So one wouldn’t expect them to go extinct from genetic defects that come to the fore because of inbreeding. However, the question of whether inbreeding has affected their health will have to wait until they decide the rest of the world is worth saying hello to.