Not trying to be funny, either, but how could an isolated population, of a severely remote/xenophobic island, not just disappear due to the side effects of inbreeding? Do secluded populations eventually become immune to the mutations?
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> Not trying to be funny, either, but how could an isolated population, of a severely remote/xenophobic island, not just disappear due to the side effects of inbreeding?
Inbreeding is only a problem if it happens over many generations of closely related person (think your cousin or closer for many generations). A single brother-sister pair in a family tree is unlikely to do much harm beyond making family reunions a bit odd.
[Minimum viable population](https://en.wikipedia.org/wiki/Minimum_viable_population) studies use a rule of thumb called the “50/500” rule. Basically 50 individuals is the minimum population to prevent serious inbreeding issues, and 500 is the point where you are reasonably safe though of course this is an overgeneralization and not reliable for all species.
> Do secluded populations eventually become immune to the mutations?
That isn’t how it works. A mutation is either bad enough to prevent reproduction or it isn’t. If it isn’t then the mutation can carry on, if it is… then that’s the end. There’s no immunity, just the athematic of reproduction.
The answer to this depends on a couple of things. There is a 50/500 https://www.britannica.com/science/50-500-rule rule that we can more or less take as a estimation. The people who live on this island came from somewhere else so their starting population could have been larger than 50 but probably not 500, although that is speculation. So if they had 50 people and they had traditions and taboos about marrying children or siblings they should be able to survive fairly well without horrible mutations. Although they will have mutations, but those bad mutations will not survive like say a Habsburg did without a large infrastructure and people tending to them so it will not enter the population permanently.
The estimated population of North Sentinal Island is 50-400 people. Depending on how careful they are with genealogy and how okay they are with polygamy, they might be able to avoid inbreeding altogether. Which is good, because inbreeding isn’t something you can become “immune” to.
Inbreeding is bad because over time, small genetic issues compound and become more and more expressed as the gene pool feeds back into itself. It’s possible to implement some kind of eugenics system wherein those with genetic defects aren’t allowed to reproduce, which would reduce the risk of inbreeding. But that’s kind of dystopia nightmare-fuel.
Yes and no. They aren’t inbred enough to create severe deformities, but they likely are more prone to several genetic diseases.
See in biology there is a concept known as “minimum viable population” or MVP for short. Essentially there are two numbers. The smaller number is the minimum number of individuals required to prevent immediately harmful inbreeding like you might have heard of in the royal families of Europe where severe physical deformities and other birth defects were reasonably common. However there is a second number in MVP where it is the minimum population required to prevent more invisible harmful genetic conditions or the loss of otherwise beneficial genes.
The old rule of thumb was called 50/500 for the two number of the minimum viable population. However, more modern complex measures take into account things like gestation, environment, and a couple dozen other factors. Allowing for much smaller or larger minimum viable populations.
Inbreeding doesn’t guarentee mutations. It only increases the chance that a mutation will be passed on since both parents are likely to have it. Also, not all mutated genes are speices ending.
The side effect of inbreeding is that your child have higher chance of express bad recessive gene. The good thing of inbreeding is that you know who had bad genes and exclude them from the gene pool.
Habsburg is the worse because of how the way their inheritance rule works, they cannot get rid of individual who express bad genes. Unlucky for them, many of those defective member end up on the throne, but many of Habsburg member does not have as much health issue despite equally inbred.
Australian aboriginal people manage to prevent inbreeding by asigning everyone letter at birth (its not a letter but I’m using that to simplyfy my explanation)
So everyone is either A B C or D.
Certain letters cannot have kids.
So A can only marry C and D etc.
Im really simplyfying it but they have used that system for eons and it works to stop genetic mutations caused by inbreeding.
Maybe the sentinel people have something similar.
Primitive doesn’t mean stupid.
There’s a really good British documentary on utube about the high rates of people born with mental/physical issues caused by first cousins marrying, within the UK Indian communities.
One of the problems is first cousins are marrying then their children are marrying and so on.
No. Inbreeding does not cause mutations and it’s not possible to become “immune” to mutations.
Inbreeding is harmful because it shrinks the number of genetic variants available in the population. If a genetic variant exists that is rare or uncommon in the general population, when it exists in the inbred population it’s much more common.
All inbreeding means to the Sentinelese is that certain genetic diseases are more common among them. It’s quite possible that they don’t naturally have very long life spans or an environment where these issues are particularly detrimental. Perhaps some lead to high infant mortality, but they just have many children.
However, they clearly are self-sustaining. We don’t know how big the Sentinelese population is either, so perhaps it’s large enough that the inbreeding effect are not so terrible.
I’ve never heard about them. How do you know about them?
Ancient populations were also pretty ruthless in exposing children with any sort of defective. The viable ones who could contribute to the group’s welfare might be left alive but not allowed to marry, etc. People are sharp-eyed and would quickly learn the rules about what level of inbreeding was too much. Some of the tribal cultures still have the most elaborate rules about who you can marry.
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