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.
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