How did pre-industrial tribal societies – for example Inuits, manage to deal with inbreeding even though they were small in size and lacked outside contact?
In: Biology
Most Alaska native groups had two moieties (subgroups or clans) and you couldn’t hook up within your own. In doing so, your closest legal hook up would be a cousin. Add to that some fresh genes from neighboring tribes every so often, as other people have mentioned. It was enough to keep the population running fairly healthy for an extended period. Not necessarily perfect.
Australian Aboriginals have a complex system in which you are given a ‘skin name’ determined by your parents’ skin names. This name determines who you can marry and who you can’t and it ensures couples are not closely related. It is still in use in some parts of Australia to this day, and has been for 50k plus years
Those small tribal societies were hunter gatherers, and therefore nomadic. Makes it easier to meet other families and tribes when you have to roam a few hundred miles every year. And then you have cultural practices like polyandry and “wife stealing” (eg in the Inuit case) to reinforce the notion that you should mate outside the clan, and you’re all set.
Along with answers above, you also need to consider that up until recently, we were very open to nature dictating things.
So compromised genes from inbreeding that manifested as a complication may not live long enough to matter, or would be lost in the shuffle. After all, if you’re bringing food home, who cares if your teeth are a bit screwy (before modern dentistry especially) or you had webbed toes, or some type of genetic predisposition (before we figured out genetics especially).
With infant and maternal mortality rates as high as they were for these people it mostly didn’t matter.
Well, many such groups have dealt with issues associated with inbreeding. It’s not like an instant thing though, you could go generations with no issues at all, or only a few unlucky ones who wind up with the bad genes. Also, it’s pretty common for such tribal societies to have their daughters marry into neighboring tribes, adding more distant blood into the mix.
But, it’s not like inbreeding will instantly lead to habsburg jaws or the hills have eyes, it just slowly raises the probability of certain issues over time.
There is a Brazilian tribe that create small villages of two big huts (hut #1 and hut #2) and each Hutt have a maximum capacity of 50 people. People of hut #1 can only marry people of hut #2 , and they move to the hut of the male family of the marriage. When the village 100 people or a Hutt get more than 50 people, they start another village with new two Hutt, and send only unmarried people there.
They used an app on their phones which told them if they were about to marry/sleep with a close relative.
Even pre-industrial tribal societies had plenty enough contact with other people for inbreeding to not be an issue. The idea of groups of people being wholly isolated is almost entirely untrue. There isn’t evidence that inbreeding has been an issue in past tribal societies.
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