Finding the genetic 'Adam' and 'Eve.'

in genealogy •  4 years ago 

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Unrelated to any current events, here are some interesting bits from genealogy and genetics.

If you trace back through your mitochondrial DNA (inherited almost exclusively from your mother), you'll eventually reach the most recent female that is an ancestor of all humans alive today. This "mitochondrial eve" is estimated to have lived somewhere between 120,000 and 156,000 years ago.

If you do the same for Y chromosomes, you eventually arrive at "Y chromosome Adam". The timing is less precise, between 180,000 and 580,000 years ago. These estimates are imprecise (obviously) and change as our knowledge of human genetics improves.

https://en.wikipedia.org/wiki/Mitochondrial_Eve

Note that the identity and antiquity of these individuals changes over time, it becomes more recent as lineages go extinct, like surnames disappearing.

It surprises some people that Y Adam was dead for at least 20,000 years before M Eve was born. It's a byproduct of using the biblical names, there's no reason to expect them to have lived near the same time or place.

Y Adam and M Eve were obviously not the only people that were alive at the time, nor the only ones with living ancestors today...they're just the most recent members of everyone's matrilineal and patrilineal branches, which can be thought of as the two farthest-out branches of an immense family tree.

But how far back would you have to go to find the most recent person who is an ancestor for everyone alive today? Surprisingly, only about 3000 years. We have no idea who it was, but the math tells us it has to be much much more recent than M Eve.

https://www.bbc.com/news/magazine-19331938

Now here's my favorite part. This one really twisted my brain for some reason. Go back 3,000 years, and this guy (it was probably a guy) is the latest person to be an ancestor of everyone alive today. Obviously, both of his parents were, too. And all 8 of his great grandparents, etc.

This means that at some point farther back, everyone on earth at that time and earlier falls into one of two categories: ancestors of EVERYONE alive today, or ancestors of NOBODY alive today. Nothing in between, all or nothing.

Take that logic far enough in the future, if we don't go extinct, and there will be a time ("X") when everyone on earth has either zero descendants at time X, or is an ancestor of everybody on the planet at time X.

I know I'm in the first group. There's no way to tell who is in the second group.

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