After 32 generations (~800 years) you have more genealogical ancestors than there are base pairs in human DNA. There literally isn’t enough resolution to store a “record” of each of your ancestors, even if you inherited exactly 1 base pair from each ancestor.
Additional complications make it an even shorter timeline. After about 8 generations, you share no more DNA with your ancestors than you do with a random stranger.
Politically this should be more well known. Of course, racists and fascists rely on “blood quantum” arguments to justify racial or ethnic oppression. But they don’t invent this idea of strict genetic identity. It’s latent in the population.
Leftists should more frequently call out genetic tests like 23andMe as inherently racist because it’s based in race science nonsense. It may not be as obvious as Nazis invoking aryan genes or whatever; but it’s still just as incorrect when your aunt at Thanksgiving talks about how she discovered she’s 2% Choctaw or whatever
Don't discount inbreeding tho. Not just cousins or whatever, but villages and groups of villages. Peoplehave gotten increasingly mobile over time of course but the reason there are groups of folks that look a bit different from one another is that we split off for a little while and became semi-isolated.
PS this isn't race theory, just genetics and a recognition of human variation. We are all modern humans and overall the same, our differences are very minor. One example would be lactose tolerance (which is the less common thing for humans to have than lactose intolerance) which has popped up a few times in human genetic history but did not spread out over the whole population in a couple thousand years.