How are the small, remote settlements of the world (i.e. upper Greenland, Nunavut, Pitcairn Island, Tristan de Cunha) able to avoid a completely incestuous population?
In: 138
Tldr: you need a minimum population of somewhere between 100-500 to prevent inbreeding in any animal population (exact figure unclear).
From a practical point of view, a lot of it is talking with family to check who’s related to who (“hi gran. Do you know X!” “Of course, they’re your 2nd cousin. Why?” “…… nevermind. Doesn’t matter. I need to make a phone call”), and now specific technology that has been developed to check these things.
Geeky science dna bit:
There is a concept of “minimal viable population (MVP). It’s the smallest population of any animal that allows inbreeding to be avoided and to reduce something called genetic drift. Genetic drift is to do with changes in the variation of different genes in a population so you can ignore it here, I just mention it because the “rule” I’m going to talk about has a second number that you might wonder what it is
The is a rule of 50/500 that says you need a minimum of 50 people to prevent inbreeding (the 500 is to do with genetic drift). At 50 people/animals you can avoid inbreeding potentially for many generations. However, ultimately there will be inbreeding if the population is that low.
This rule has been further explored and the evidence now points to needing a bigger population for most species. Figures like 100/1000 or even needing a minimum of 500-1000/5000-10,000 people to continue a population indefinitely without major issues.
There will be point however where there will be some overlap in families, but from a human view point, at which point do you decide the connections are ok? What if you found out you shared great-great-great-great-great grandparents with your partner and are there for 6th cousins (share about 0.1% dna as a result of that connection)? What about if it was 5th, 4th or 3rd cousins?
Actual practical stuff that humans use:
So the above is just going with the genetic and numbers, and working on the idea that new people don’t come into a population.
In practice, people move, new people will move to some of these places sometimes.
But the biggest factor with humans now is just us talking and being social animals. We likely know many of our cousins and just through word of mouth can find out if we have other connections. If you’re from a smaller community where this may be an issue, you might specifically ask family members if you are related to someone your interested in.
I have a friend who is from a Caribbean country that although it doesn’t have a small overall population, they were from a smallish recognisable genetic group within that island. They had met someone they liked and been on a few dates, and then the thought came to their head that maybe they are related (they actually met in the uk rather than back home). My friend asked their gran who let the know, as far as she knew they were related. My friend found out later, that his now wife has done this same thing, asking her gran!
You then get modern technology and some areas have developed apps that you can check.
You then also get areas where the population is so low that it’s not going to be viable long term. The Pitcairn Islands currently has less than 50 people. The 2020 census said there were only 7 people less than 20years old (only 2 of them less than 10years old). The government tried to attract new people to the island but with no real success. In the longterm, the population isn’t sustainable unless something changes
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