I’ve just discovered a major breakthrough in the Mitochondrial Eve story.
Apparently, and this is surprisingly important, Mt DNA is not a neutral gene. This means it is subject to natural selection. Less efficient Mt DNA types will get selected out. Suddenly, a lot of conflicting information from various sources stars to make sense. It also means that the absence of wildly different Mt DNA types that could have come from Neanderthals or Homo Erectus is totally meaningless, as they would have been selected out by the newer, better Mt DNA type from Africa. Multi-regionalism and the hybrid hypothesis are suddenly back in play.
The only thing the spread of Mt DNA now tells us, is it’s own spread. Think of the difference between a small twig in a stream, it is at the mercy of the currents (like a neutral gene). Then think of an insect or fish in the same stream. It can move in any direction, with the movement of the water only exerting a pressure to move in one way. This is the effect natural selection would have. What this means is that Mt Eve was probably NOT the result of a population bottleneck, she just had a mutation for a more effective energy conversion in her cells. And, as beneficial mutations tend to, this spread all over the world. What it doesn’t mean is that one group of Africans spread out all over the world, and that we are all really closely related.
It also raises the question, “are Y chromosomes neutral genes?”. I’m going to go out on a limb and say, probably not. There are genes for various functions on the Y chromosome, Adam could just have produced more motile sperm. This would mean that Y chromosome Adam simply had a mutation that gave his DNA an advantage, so that it spread. Maybe it made him taller, or faster. It could be anything. It doesn’t mean he was at the head of a small bunch of intrepid pioneers colonising the planet.
Add this to the fact that some very ancient X chromosomes have been discovered in Asia and Africa, that date back one to two million years, and you can see how the recently out of Africa theory is look very shaky indeed.
Adam and Eve….never existed.