Joe Pickrell‘s paper, Ancient west Eurasian ancestry in southern and eastern Africa, is finally out. Readers of this weblog will be aware of its broad outlines, as it is been circulated as a preprint. He’s graciously acknowledged the response on this weblog and Haldane’s Sieve as informative feedback in the final paper. Why? I think it’s “because intersectionality,” as they say. The topic that is being explored by statistical historical genetics is by its nature multidisciplinary, and biologists bringing powerful and abstruse techniques to the field need the input of those with “thick” area knowledge to truly open all the windows which can shed light upon a topic. Startling scientific insights become much richer, and inform our picture of the past, when integrated into the full body of previous historical scholarship.
After reading Peter Bellwood’s First Migrants, I am now tempted to coin a phrase: “Nothing in history makes sense except in light of demography.” This is obviously too strong a phraseology, but if the methods of modern statistical genetics are correct in the peculiar inferences they’re making, then we do need to rewrite the history books to a great extent. Or at least expand the purview of what we consider history, and how we understand what archaeology is telling us. For example, Africa is often represented in the public imagination as the ur-continent: unchanging, everlasting, primal. But the results we see from genetics, the relative similarity of populations from Nigeria to the South Africa’s Eastern Cape, and the minimal impact of the ancient hunter-gatherers on the ancestral variation of these people, attest to recent and revolutionary changes in the character of the population of the African continent, which belies its static perception. This recent paper, as well as Luca Pagani’s result on admixture within Ethiopia, implies that demography has wrought drastic change among the non-Bantu people of eastern and southern Africa, pushing them to the margins of history. To put it more starkly: when the pyramids of Egypt were being built the vast continent to the south would have been unrecognizable in terms of its human geography to a physical anthropologist.
And this is not just a feature of Africa. In First Migrants the author recounts a personal communication from a scholar who has assembled unpublished data on the skeletal remains and ancient DNA from a community in northern Vietnam ~4,000 years ago. This seems to have have a frontier agricultural settlement, on the edge of rice culture. While the majority of individuals exhibited the body type and skull form of modern Asians, a minority manifested what the author terms “Austro-Melanesian” physical attributes. And critically, the ancient mtDNA haplogroups break down in the exact same ratios as the morphological remains, with a majority shared with modern Northeast Asians, but a minority of a type limited to Southeast Asia, and usually inferred to suggest common heritage with the peoples of Australasia and South Asia.
What the researcher above captured was a snapshot in time, freezing a moment which was transitory, as the ancient substrate of Southeast Asia was absorbed into the advancing wave of farmers. One could go on in this vein. We know so much more than we did in the past, and not to be hyperbolic, but some of what we know suspect resembles Conan the Barbarian more than the wildest imaginings of prehistorians of the past generation. But that’s one of the great things about scholarship: it can confound pedestrian expectations. And on occasion which captures the ineffable aspects of truth obscured should astound us.
Citation: doi:10.1073/pnas.1313787111
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