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byllz t1_iv3tw9u wrote

Reply to comment by za419 in Why don't we have Neandertal mitochondrial DNA? by nodeciapalabras

Mitochondrial Eve likely hasn't changed in quite a while. With rapid population increases since agriculture became a thing, lines are much less likely to die off.

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za419 t1_iv3yty3 wrote

Ehhhh... Maybe.

Fertility rates among some demographics is dropping pretty quickly, which could easily end a line.

And lines end by chance too - even with an increasing population, an endangered line just needs a few accidents, or a few lesbians, or a few child free daughters, or even just a random generation of sons to come to an end.

Now, most lines that end won't be ancient enough to move mitochondrial eve - since it can only move down if exactly one of her daughters has a surviving female line.

But, the point is that "Mitochondrial Eve" isn't a permanent title, or one specific super important person - it's flexible. Who she is changes with time.

A lot of people overstate the importance of Mitochondrial Eve - not that she isn't important to our development, obviously everyone on earth literally has a part of her in us - but she isn't unique. If you went back in time and shot her, another woman would take her place, and you'd come back to an earth that's probably very different, but probably also is still populated by many humans - And there are probably plenty of humans back then you could have shot and changed history even more.

Indeed, any given woman alive today who has/will have multiple daughters could become mitochondrial eve at some point in the very distant future - It's not impossible, though it's kind of unlikely at this point.

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byllz t1_iv4038c wrote

It isn't just the growth, it is the sheer population. Suppose you had an ancient generation that was down to 2 women with matrilinear descendants. One line accounts for 99.9999% of the current population, and the other the rest. If your world population is 1,000,000, then the likelihood you will have a new Eve pretty soon is high, as there is currently only 1 woman left of the minority line, and the chance of any given woman not having daughters, or her daughters not having daughters is pretty high. But if the world population is 8,000,000,000 then the chance of a new Eve is low any time soon as you would need 8000 such occurrences.

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