Out of who knows where

In The New York Times, DNA Turning Human Story Into a Tell-All:

The tip of a girl’s 40,000-year-old pinky finger found in a cold Siberian cave, paired with faster and cheaper genetic sequencing technology, is helping scientists draw a surprisingly complex new picture of human origins.

The new view is fast supplanting the traditional idea that modern humans triumphantly marched out of Africa about 50,000 years ago, replacing all other types that had gone before.

Instead, the genetic analysis shows, modern humans encountered and bred with at least two groups of ancient humans in relatively recent times: the Neanderthals, who lived in Europe and Asia, dying out roughly 30,000 years ago, and a mysterious group known as the Denisovans, who lived in Asia and most likely vanished around the same time.

Their DNA lives on in us even though they are extinct. “In a sense, we are a hybrid species,” Chris Stringer, a paleoanthropologist who is the research leader in human origins at the Natural History Museum in London, said in an interview.

First, for reasons of novelty we are emphasizing the exotic tendrils of the human family tree. Even Chris Stringer, the modern paleontological father of “Out of Africa,” is claiming we’re hybrids! But let’s not forget that non-Africans are the product of a very rapid radiation out of the margins of the Afrotropic ecozone within the last ~50-100,000 years. I am not entirely sure that this is as true of Africans (recall how extremely basal Bushmen are to the rest of humanity; they seem to have diverge well before the “Out of Africa” pulse).

Second, the old model was way easier to write about, even if there were confusions like the idea that mtDNA Eve was our only female ancestor from 200,000 years ago in the past. The new paradigm leaves one with awkward and unhelpful turns of phrase. For example:

But Dr. Reich and his team have determined through the patterns of archaic DNA replications that a small number of half-Neanderthal, half-modern human hybrids walked the earth between 46,000 and 67,000 years ago, he said in an interview. The half-Denisovan, half-modern humans that contributed to our DNA were more recent.

How to make sense of this gibberish? I suspect that the author didn’t have a good idea how to translate a particular population genetic statistic, and its importance to assessing time since admixture, into plainer prose. I have no idea either!

In other news, i09 has an interesting interview up with Rebecca Cann and Mark Stoneking. These two were heavily involved in the mtDNA Eve controversies of the 1980s. Nice capstone to an era. Like Stringer, even they admit the likelihood of a necessity to modify the simple “Out of Africa” with replacement model.

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