A few days ago Spencer and I recorded a “predictions for 2020s” episode for The Insight, before we go back to “regularly scheduled programs.” One of the topics (of ten) we discussed is that the old “Out of Africa” model is going to be marginalized/complicated.
What did we mean by this? Some of the hints are already present in David Reich’s Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past. If you look at and analyze genome-wide data, especially ancient data, there are just too many strange results to be accounted for by our current consensus understandings. There are new things we’ll learn. And some of the old things will be wrong. We just don’t know what.
In the 1980s and 1990s, and into the 2000s, the “Out of Africa” narrative was one that the “community” of paleoanthropology went hard into (and to a lesser extent human geneticists). Perhaps too hard. Not only is there “archaic” admixture outside of Africa, but there is “deep structure” within Africa. At some point, there are too many epicycles, and there needs to be a major model revision.
Over ten years ago Dienekes Pontikos presented what I thought at the time was a “crazy” paradigm of back-to-Africa migration. Though I’m still not sure of that particular model, I think there is a high likelihood of reciprocal gene-flow between Africa, and Eurasia, especially Western Eurasia, within the last few hundred thousand years. The debates around Y haplogroup E, which is modal within Africa, but also present with deep lineages in Eurasia, shed light I think on some of the complexity.
Instead of a single “Out of Africa” movement 50-60,000 years ago, there seems to have been a sequence of events 50-100,000 years ago which resulted in the population genetic patterning that we see around us. Some of it is the classic wave expansion from a small founder group for non-Africans, but within Africa it seems there were also expansions and admixtures, albeit more complicated, continuous, and long-standing. Some of the deepest branches within African population history go back hundreds of thousands of years, but much of it dates to expansions with closer affinities to non-Africans 50-100,000 years ago.
Sometimes it can be exciting to say that the question is the answer….