Cousins, part 1

In The Human Blueprint: The Race to Unlock the Secrets of Our Genetic Script, science writer Robert Shapiro at one point explains that if you pick any two people at random on the street, it’s nearly impossible to go back more than six hundred years before finding a common ancestor. Yes, even if the two people appear to be of completely different races.

There are several caveats, the biggest being that is isn’t impossible, it’s just that the probability has gone down to such an incredibly small number (there were a bunch of zeros between the decimal point and the 1 in the percentage he gave), that for most purposes it might as well be impossible. There are pockets of human population that have been isolated for many more generations than covered in 600 years, of course. But they’re very small.

He also explained how for most of human history most people lived their entire lives within 30 miles of the place they were born, which was usually the same community where both their parents lived, and their parents before them, and so on. So most everyone in a particular community were related to each other, at least distantly.

That doesn’t contradict the previous statement, beacuse all you needed was a small fraction of people to occasionally wander far afield before finding someone to have a family with, and in a matter of a dozen or so more generations, most of the population of said insular community have inherited at least some genes from that one wanderer, and are now all distantly related to everyone back in his old community. They just don’t know it.

Humans have been doing this for hundreds of thousands of years, long before modern technology made world travel and relocation commonplace.

In other words, we’re all cousins, of one sort or another.

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