An interesting new opinion piece by Chris Stringer in which he affirms the recent Out-of-Africa theory. Some predictions of the multiregionalists were certainly wrong (e.g., they did not predict that East Asians would have any Neandertal ancestry, let alone more than Europeans; and the ancestry of mankind may be even more jumbled than they'd imagined as e.g., it is not Siberians that have regional continuity with Denisovans but rather the faraway Papuans and Australians). On the other hand, the evidence does seem to point for a mostly African origin of Homo sapiens with important details of when and how that remain to be filled.
The fundamental question for me is the balance of divergence and synthesis in human history. Certainly, the fact that Denisova cave and thereabouts in Siberia had at least four divergent human lineages in the last 100-40 thousand years (unknown archaic Eurasians, Denisovans, Neandertals, and finally modern humans) makes modern Eurasians look like twins by comparison. In more recent times, Europeans of a few thousand years ago living in Sweden were more divergent from each other than any two European populations living today. And, while many models would have modern humans and Neandertals splitting from each other and going their separate ways until very recent times, this is hard to reconcile with the fact that apparently Neandertals and Africans became more similar over time during the period where they were supposedly diverging from each other. Was the situation in Africa any different? Morphology does not suggest homogeneity for that continent either.
Certainly, both replacement and gene flow have played a role in human history. The "English" and "Spanish" packages were assembled in Europe by gene flows from hunter-gatherers, farmers, and more recently Anglo-Saxons, Celts, Vikings, Goths, Romans, and Celtiberians (to name a few), but was then exported from Europe. Human history probably abounds in examples of populations that emerge out of a multiregional matrix (even if that matrix does not encompass the entire globe) and then explode in population numbers due to a lucky break or some behavioral or technological advantage.
Trends in Ecology & Evolution Volume 29, Issue 5, p248–251, May 2014
Why we are not all multiregionalists now
•DNA data show that archaic introgression into modern human genomes occurred.
•Such introgression is claimed to support the multiregional model for modern human origins.
•This introgression is also claimed to support the lumping of distinct human species into Homo sapiens.
•Comparing models and data still validates a recent African origin model for modern humans and the use of a restricted diagnosis for H. sapiens.
Recent revelations that human genomes contain DNA introgressed through interbreeding with archaic populations outside of Africa have led to reassessments of models for the origins of our species. The fact that small portions of the DNA of recent Homo sapiens derive from ancient populations in more than one region of the world makes our origins ‘multiregional’, but does that mean that the multiregional model of modern human origins has been proved correct? The extent of archaic assimilation in living humans remains modest, and fossil evidence outside of Africa shows little sign of the long-term morphological continuity through to recent humans expected from the multiregional model. Thus, rather than multiregionalism, a recent African origin (RAO) model for modern humans is still supported by the data.