meritocrat

Since mitochondrial DNA in our species had been discovered to date back to groups of people in Africa, does that place a great (though perhaps not irrefutable) amount of evidence in the Out of Africa theory?

Also, if the Multi-Regional theroy were true, why did homo erectus/ergaster evolve as the same species across the Earth? For example, modern humans and the Neanderthals were believed to have evolved from homo heidelbergensis. If two distinct species could emerge from a single species in two differing parts of the world, then why (assuming the Multi-Regional theory is true) did not different species arise from homo erectus populations?

Walross

Hi meritocrat,

I'm no anthropologist, but I do have an interest in the subject, so I'll take a crack at answering your questions. Please take what I say with one large grain of salt as it is all a little vague in my head.

IIRC, the mitochondrial DNA evidence shows, with a great amount of certainty, that we all evolved from a common ancestor at some point in the (relatively) recent past. The question, however, is when this was. I seem to recall that there was some dispute regarding the change rate of mitochondrial DNA that could place that common ancestor as far back as 1 million years ago rather than the 100,000 ya that is usually cited. 1 million ya would be consistent with the multi-regional hypothesis.

A small point of difficulty for the out of Africa hypothesis is that fossil evidence in East Asia seems to show a smooth and continuous line of evolution from H. Erectus to archaic H. Sapiens. I say "seems" because, the fossil record can, of course be misinterpreted.

If the multi-regional hypothesis were true, I don't see a huge problem in the fact that the end product of the evolution of disparate groups of H. Erectus are inter-fertile. Remember that the classification of "species" is a tricky business in some cases. Members of different but closely related species may be inter-fertile, while different groups within a species may not be able to mate at all (think of dogs, all of which are considered one species even though some breeds of which cannot mate with members of another breed. Some dogs can, however, breed with coyotes for example). Keeping this in mind, I think the multi-regional hypothesis is plausible.

All that said, I suspect the out of Africa hypothesis, or some variation of it will prove to be the correct one in the end.

If I'm wrong about anything here, please correct me as I'm but a layman on the subject (which I find fascinating). Regards,

Walross

Valentine Pontifex

If the multiregional hypothesis is correct then all the "species" you mention are members of the same species. So your question is sort of moot.

Gringo

This web page had called an intresting article on this subject, A Diffusion Wave Out of Africa. The article discusses evidence for low rates of interbreeding between Homo sapiens and Homo erectus and neanderthalensis. The article goes on to discuss how mt Eve and Y chromosome Adam could be so recent, and yet Homo erectus and neanderthalensis' genes which had strong selective advantages could exist today.