This argument can only be true for contemporaries of mitochondrial Eve and Y-chromosome Adam. But we don’t know if the mitochondrial Eve and Y-chromosome Adam of the future generation we’re talking about happen to live today, will come after us, or came before us. If they came before us, then it’s perfectly possible that some, but not all members of the future generation are descendants of a given person alive today (who has, or will have, children - childless people will obviously be nobody’s ancestor).
If you trace back the DNA in the maternally inherited mitochondria within our cells, all humans have a theoretical common ancestor. This woman, known as “mitochondrial Eve”, lived between 100,000 and 200,000 years ago in southern Africa. She was not the first human, but every other female lineage eventually had no female offspring, failing to pass on their mitochondrial DNA. As a result, all humans today can trace their mitochondrial DNA back to her. SOURCE
Thanks for understanding.
One thing to note about Mito-Eve and Y-Adam is that there were almost certainly people who lived more recently (as in thousands of years more recently) than those two who are also the ancestor of every living person. Those two are not special in this regard.
If you trace back the DNA in the maternally inherited mitochondria within our cells, all humans have a theoretical common ancestor. This woman, known as “mitochondrial Eve”, lived between 100,000 and 200,000 years ago in southern Africa. She was not the first human, but every other female lineage eventually had no female offspring, failing to pass on their mitochondrial DNA.
This would make sense- once humans began expanding out of Africa into the rest of the world, it becomes statistically much harder for a random person to have offspring who spread among neighbours and so on replacing all female lineage with their own. The “Eve” effect probably works best in smaller populations. Since there was allegedly a population bottleneck back about 70,000BC it would be a lot easier then for a single line to survive and others to die out. Each infertile female or “all boys” family has a larger impact on the line survival when the numbers are small.