I am interested in knowing if you attempted/did the following or could extrapolate a conclusion based on the information you have from the studies you did:
Let us imagine that "Eve" was not created or died out. Does another female lineage replace "Eve's" and populates the earth?
Here's a difficult concept, for me, at least. "Mitochondrial Eve" was
a real woman. But we only know of her indirectly, through the Mitochondrial DNA that has descended from her. And her identity is not as some individual, but more like a job description. It's a functional position, like "Queen Mother", or "Secretary of Ancestry". By definition, this Eve had to have had at least two daughters, (two, at least, who survived to reproduce) and at least one of those daughters had a mutation in in her mDNA that made it distinct from that of her sisters'. It need not have been a large mutation, or one of any functional consequence. It only need be traceable.
Through the generations, this bifurcation in DNA sequences continued, occasionally producing other bifurcations, until there is now a scattering of six major subgroupings, or haplogroups
. Interestingly, Non-Africans all tend to host a single haplogroup, while Africans distribute the other 5.
Let's assume that a global disaster occurred, and all Europeans and Asians were to suffer extinction, wih only a few African groups surviving. Would the current Mitochondrial Eve still be valid?
No. The person who we now call Mitochndrial Eve would still have existed, of course, but the title
would pass to one of her descendants, the one who gave birth to the most distantly surviving bifurcation.
There's another possibly difficult point: Mitochondrial Eve is NOT our only female ancestor. The only DNA she necessarily contributed to all of us is that of our mitochondria. Mitochondria are only passed down from mother to daughter. We had many other female ancestors, but all of those necessarily included at least one male in the ancestral line. It's highly possible that she contributed NO nuclear DNA, some of which could have been supplied by any of her contemporaries. Because nuclear DNA experiences recombination and mixing, and can come from either males or females, there is no way to trace it into the distant past (with the exception of some marker sequences, perhaps). Her descendants did not populate the Earth, because the Earth (or at least Africa -- and Europe and Asia if one counts Neandertals and Denisovans) was already populated. She merely supplied a single easily traceable genetic marker. Plenty of others could have supplied the rest.
So what if Mitochondrial Eve had never existed? Well, if that woman happened to be named Ayla and lived in the Sudan 200,000 years ago, and if someone went back in time and accidentally landed their time machine on top of her -- the human race would not suddenly have never existed. There were plenty of other women who could
have been Mitochondrial Eve had their mDNA had the right opportunities. Maybe a woman who lived prior to Ayla, possibly her grandmother, might have been the title-holder. Maybe her cousin. Maybe a distant relative in Ethiopia. As I mentioned before, inheritance in single lineages is not necessarily a competition based on fitness. It can very well be a contest of equals. And if one competitor is eliminated, there are many others standing by.