Problem:
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 image 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.
Required:
Question 1: 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)?
Question 2: 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?
Question 3: 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... please suggest the correct answers.