Apparently, all living humans are matrilineal descendants of a single woman who lived 200,000 years ago. She is called Mitochondrial Eve. But at the time she lived, there was a different matrilineal ancestor that all living humans shared. And between then and now, I imagine many other women have been Mitochondrial Eves of the human population that lived at a particular time. What I'm wondering is what kinds of events would cause a different, more recent matrilineal ancestor to become the Mitochondrial Eve of all living humans? One scenario I can imagine is that the human population is on the brink of extinction and literally only a few people survive. Because there are so few people alive, I imagine that the chance that they share a more recent matrilineal ancestor is high. Are there other scenarios possible? Does the chance of a new Mitochondrial Eve emerging decrease if the human population is large (billions) instead of small (hundreds or thousands)? Suppose that the human population will not decrease, is it likely future human populations will ever have a different Mitochondrial Eve than the current population? Does it depend on the amount of people that migrate? The same questions could be posed for Y-Chromosomal Adam and the most recent common ancestor of all humans, I guess...