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Comment by lifeisstillgood | Hacker News Reader

I always get confused here between "Eve" and MRCA.

AFAIK "Eve" is not what we are talking here - that is not as identifying one person who is the ancestor of all living people, but that if we go back to the time of David, then he, and 80% of everyone alive at the time (approx 1 million) MUST be ancestors of everyone alive now. That is some of his DNA and some of everyone elses DNA at the time is in me.

That is pretty weird.

The other thing that gets me is that till agriculture, it seems human population was stable at around 1 million. Then it started to grow to 1 billion by 1800. Freddie Mercury could sing to the whole population of earth in three concerts.

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I don't think the difference you're talking about is real. "Eve" is mitochondrial Eve, the most recent direct female-line ancestor-- the first human every woman can say was her mother's mother's mother's et cetera. There's a corresponding Y-chromosomal Adam; they probably lived 100-200,000 years ago, but not at the same time.

But of course if you're descended from her, you're descended from her parents, and her mate's parents too; nobody came from just one person. Each one out of our millions of common ancestors is an Adam or Eve by the popular definition: Every human being alive is descended from them. If they had not conceived, no one currently alive would exist. There was never a biblically singular Adam and Eve.

So, the first person who was the MRCA-with female lineage only, ie the earliest woman who was the female ancestor of all living people, was 100,000 years ago.

But the earliest ancestor (female / male / mixed lineage) was only 3000 years ago.

(i.e. the first, had to have daughters only, the second, more recent could have daughter then grandson then great-grandson etc)

So, 3000 years before we can say anyone definitely was the ancestor of all, and there would be a lot of them. And 100,000 years before its female lineage. Then pretty much everyone is a common ancestor, back to plankton. And Dinosaurs!

More or less, except 3000 years ago travel was far more of an issue. But, somewhere in the ~2,500-30,000 years it's probably true.

Also, with a population of 1 million people a female line 'wining' is much more likely than with a ~6 billion people population that probably will not happen again for a vary long time without some awesome mutation.

> the first human every woman can say was her...

I think that's a typo, should be: "...first woman every human...". All of us have Mitochondrial Eve as our matrilineal MRCA, not just those with two X chromosomes.

Yeah, good catch. I was hoping no one would notice that goof :)

Yes this is the key - people won't have just one ancestor but many millions.

> More specifically, imagine the simplest case of a population of a constant size - say a million (the approximate size of the Holy Land at the time of Jesus).

The total human population was greater than 1 million.

You're referring to the year 0 CE, he's referring to the advent of agriculture around 10000 BCE.

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