Understanding migration through ancient DNA
16 June 2022
Last update: 15/06/22 13:12
One of the most exciting developments in archaeology over the past few years has been the rapid growth in population-scale studies using ancient DNA. Genome-wide analysis of ancient individuals can now provide extraordinary insights into issues of population diversity, movement, and continuity in the distant past, enabling us to address (and even settle) some long-standing archaeological questions.
Last year, we published a paper in Antiquity dealing with the impact of aDNA analysis on our understanding of the spread of the Beaker Complex into Britain from Continental Europe in the mid-third millennium BCE. This period, which saw the introduction of copper metallurgy, distinctive beaker pottery, and a range of other cultural changes, can now also be shown to have witnessed a massive genetic turnover. Indeed, by the end of the third millennium there was a replacement of a minimum of 90% of the gene pool in Britain. It is fair to say that this represents a far higher genetic impact than any of our team had expected. This result is even more remarkable since the same study shows that the Beaker Complex in Continental Europe spread across communities with very different genetic profiles. But in Britain it was accompanied by the movement of people on a substantial scale.
The idea that major cultural changes were routinely caused by population movement has largely fallen from favour amongst archaeologists in recent decades. In part, this was due to the over-use of migration as an explanatory concept in the early days of the discipline, when almost any new burial rite, technology or pottery form could be ascribed to the arrival of new people. Such ‘invasionist’ interpretations were clearly open to political exploitation, most notoriously in the case of Gustaf Kossinna, whose theories on Germanic ethnicity and expansionism were used to justify Nazi territorial claims in the 1930s. With the development of processual archaeology in the 1950s and ‘60s, this reliance on migration as an explanatory tool was increasingly seen as simplistic and misguided.
It is this legacy that has perhaps caused archaeologists to under-theorise migration and to downplay the impact of population movement in prehistory. With the advent of aDNA analysis, however, this is no longer an option. Demographically transformative population movements can now be identified at key points in European prehistory. The westward movement of Yamnaya pastoralists in the third millennium BCE is a notable case in point. The movement of the Beaker Complex into Britain is another.
Migration is not reducible to invasion or colonisation by technologically advanced outsiders, as was often implicit in early archaeological writings. In the contemporary world, large-scale migration typically involves marginalised people displaced by conflict or climate change. The challenge for archaeologists now is to contextualise and seek to understand the demographic processes that underlie prehistoric population movements at specific times and places.
The return of the Beaker Folk? Rethinking migration and population change in British prehistory by Ian Armit and David Reich is out now (open access) in the journal Antiquity. The article authors are also the recipients of the Antiquity Prize 2022.
Image: Beaker vessel from Wetwang Slack, East Yorkshire (Wetwang/Garton Slack archive)
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It is my duty to know every corners of my country
The anti-migrationist orthodoxy of the past few decades is now revealed as “archaeological Lysenkoism”, using pre-history as a blank slate unto which are projected ideological preoccupations.
If Childe and Gimbutas and Kossinna weren’t entirely right, they were closer to it than their successors since 1950 .
As a matter of fact, the spread of the Beaker complex via mass migration and population replacement in Britain after 2500 BCE would be instantly recognizable to any archaeologist of the year 1950 or previously. They’d simply say of the aDNA evidence that it confirmed their previous theories — and it does.
Now we’re seeing desperate attempts to ‘save the appearances’, or less politely, avoid the logical implications to avoid hurt feelings and ideological offense.
For example, the 90%+ genetic turnover in Britain following 2500 BCE is often piously accompanied by pronouncements that there’s ‘no evidence’ of violence.
So, we’re supposed to think it credible that, given a glimpse of the superior ceramics and bronze tools of the immigrants, all the local men and women lost their will to live?
Became too depressed to reproduce?
Slit their wrists with their flint knives?
At about the same 2500 BCE date, aDNA has also revealed a genetic turnover in Iberia that resulted in the virtual extinction of the previous male Y-chromosome lines of descent, and their replacement with Central/North European ones, over a period of only a few centuries.
Again, we’re told that this doesn’t imply “violence”.
Let’s see… the local males were so impressed by the tall blond coolness of the Central European immigrants that they spontaneously castrated themselves?
Or were just so depressed that they couldn’t, ah, ‘get it up’ anymore?
Pots don’t -necessarily- mean people.
But quite often, they do mean people.
Because the commonest way of transferring culture, particularly in preliterate times, was to transfer the living heads that contained it. And human interactions have always involved violence; cf. Otzi the Iceman, who turned out to have been shot in the back with an arrow, or those Paleolithic massacre sites they’re digging up.
Now, it’s a general principle that just as similar causes produce similar results, similar results imply similar causes.
Let’s take that 2500 BCE genetic replacement in the British Isles; new material culture, new population.
What historical analogues are there? Where would you get a near-identical result if you did aDNA research of the same type on the human remains?
Well, southern New England between 1600 CE and 1750 CE. comes to mind.
New material culture, new population. And since we have contemporary accounts, we -do- know what produced that: a combination of novel diseases and lots and lots of violence.
As an amusing bonus, the new population was largely descended from the one that replaced the previous inhabitants of Britain forty-five hundred years before. Who’d largely replaced the hunter-gatherers in their turn, of course.
Now take examples where you get a Y-chromosome turnover of the type found in Iberia post 2500 BCE.
What are the areas where the same results occurred?
Why, in Latin America after 1492, of course.
The modern populations of Chile and Mexico, for example, have more than half their autosomal DNA traceable to Europe — Iberia, specifically.
But a very much smaller proportion of their mtDNA than their Y-chromosome lines. Local maternal lines of descent, immigrant males.
And -that- was the product of violent colonization in which immigrant males got far more favorable conditions for successful reproduction. Chile and Mexico aren’t the only examples, of course; central Columbia, Brazil, etc. show similar patterns.
The obvious inference is that the mechanisms of historical causation don’t change because there aren’t literate clerks around to take notes.
Post-1492 Europe wasn’t doing anything new or different, except for the speed and scale. This was how human beings had always interacted. QED.
Note that we’re still at it; ask them in Ukraine, or Darfur, or ask a Uyghur… but you’d better be quick with the latter.
Thanks for your comments. Please do read the article in full if you haven’t already: http://ow.ly/NEqJ50JRjB6
I understand your logic but where is the physical evidence?