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History genomics evolution demographics archaeology molecular
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Who Killed the Men of England? The written record of history meets genomics, evolution, demography, and molecular archaeology.
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more than a million men vanished without a trace. They left no descendants. Historians know that something dramatic happened in England just as the Roman empire was collapsing. When the Anglo-Saxons first arrived in that northern outpost in the fourth century a.d.--whether as immigrants or invaders is debated--they encountered an existing Romano-Celtic population estimated at between 2 million and 3.7 million people. Latin and Celtic were the dominant languages.
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Yet the ensuing cultural transformation was so complete, says Goelet professor of medieval history Michael McCormick, that by the eighth century, English civilization considered itself completely Anglo-Saxon, spoke only Anglo-Saxon, and thought that everyone had “come over on the Mayflower, as it were.”
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Working along an east-west transect through central England and Wales, the scientists discovered that the mix of Y-chromosomes characteristic of men in the English towns was very different from that of men in the Welsh towns: Wales was the primary Celtic holdout in Western Britannia during the ascendance of the Anglo-Saxons. Using computer analysis, the researchers explored how such a pattern could have arisen and concluded that a massive replacement of the native fourth-century male Britons had taken place. Between 50 percent and 100 percent of indigenous English men today, the researchers estimate, are descended from Anglo-Saxons who arrived on England’s eastern coast 16 centuries ago.
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So what happened? Mass killing, or “population replacement,” is one possible explanation. Mass migration of Anglo-Saxons, so that they swamped the native gene pool, is another.
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Yet no archaeological or historical evidence from the fifth and sixth centuries hints at the immense scale of violence or migration that would be necessary to explain this genetic legacy. The science hinted at an untold story.
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across entire fields of inquiry, the traditional boundaries between history and prehistory have been melting away as the study of the human past based on the written record increasingly incorporates the material record of the natural and physical sciences.
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The study of the human past, in other words, has entered a new phase in which science has begun to tell stories that were once the sole domain of humanists.
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Thomas had found that genetically, not one of the English towns he sampled was significantly different from the others. Welsh towns, on the other hand, were significantly different from each other and from the English towns.
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Most importantly, he found that inhabitants of the Dutch province of Friesland were indistinguishable genetically from the English town-dwellers. Friesland is one of the known embarkation points of the Angl0-Saxons--and the language spoken there is the closest living relative to English.
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The implications are profound: “Suddenly, we have all these genuine historical observations that need to be taken on board by historians and archaeologists and they raise a whole series of new questions, focusing particularly on…what is going on at the intimate level of this new civilization that is being born in the ruins of the Roman empire. The history of Europe will never be the same.”
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But most archaeologists and historians who understand the economic capacity of the era, he noted, “find such massive contributions to the English gene pool to be completely unacceptable.
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“But still, the genetic data are quite robust,” Thomas pointed out. “This is where the idea of an apartheid-like social structure comes in.” He has advanced a theory that a sexually biased, ethnically driven reproductive pattern, in which Anglo-Saxon males fathered children with Anglo-Saxon females and possibly Celtic females, while the reproductive activities of Romano-Celtic males were more restricted, is the most plausible explanation for the demographic, archaeological, and genetic patterns seen today.
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There is some support for this in ancient English laws, which indicate that Britons and Anglo-Saxons were legally and economically different even in the seventh century, long after the initial migration. Thomas cited wergild (blood money) payments as one example: “Killing an Anglo-Saxon was a costly business, but Killing a native Briton was quite cheap.” This points to differences in economic status. And differences in wealth “almost always result in differences in reproductive output,” he said. “Sometimes two- and three-fold differences.” To the extent Anglo-Saxons were able to have and support more children, this could lead to a gradual replacement of the indigenous Y-chromosome over many generations
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Simulating such an advantage, and choosing an arbitrary figure of 10 percent migration, Thomas found that the Y chromosomes of native Britons could have been replaced in the general population in as few as five generations.
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by the 1970s, he continues, scholars began to realize there never was a homogenous “nation” of Germans in northern Europe, just small tribes that coalesced along the Roman frontier in what were political and cultural, rather than biological, federations, as their very names suggest: Alemanni, meaning “all men”; Goths, meaning “good guys.”
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The Romans, scholars believed, provided a common enemy, and that unified the disparate Germanic tribes. This line of reasoning led historians to a further thought: maybe the Anglo-Saxon identity was similarly socially constructed, and not biological after all
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More recent historical scholarship, therefore, has increasingly emphasized discovering the extent to which the barbarian migrations were really a process of ethnogenesis--the creation of new ethnic identities, as the merchant’s story illustrates.
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“There is lots of evidence for it,” McCormick says. “But now you have Mark Thomas telling us that you could actually study mating patterns. That is utterly unanticipated.” The work raises a host of new questions: What was women’s role in the barbarian settlements? Were Anglo-Saxon men mating with Celtic women? Or were there women in those invading boats, and if so, how many? What happened to the Romano-Celtic men? Were they killed?
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In an attempt to explain the remarkable similarity between Frisian and English towns, Thomas and colleagues constructed a population simulation model on a computer. He tested many theories: common ancestry dating back to the Neolithic age; background migration over centuries and even millennia; and a mass-migration event that, he calculated, would have had to involve at least 50 percent replacement--the movement, in other words, of a million people.
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The Y-chromosome can be a particularly revealing signature of the past when compared to other kinds of genetic data. Among African Americans in the United States, for example, Y-chromosomes are about 33 percent European, he says, though the proportion varies from city to city. But those same African Americans’ mitochondrial DNA, which comes from the female line, is only about 6 percent European. And that, says Reich, “tells you about the history of this country, in which men contributed about three-fourths of the European ancestry that is present in the African-American population data. The data speak to a history in which white male slaveowners exploited women of African descent--a fact that is well documented in the historical record. That there is evidence of this in genetic data should be no surprise.”
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Most Americans associate Medellín with the drug cartels of that isolated region. But the remoteness has also preserved a genetic legacy that can be traced to the conquistadores. As described in a paper by Andrés Ruiz-Linares of University College London, the Y-chromosomes of men in Medellín are 95 percent European, while the mitochondrial DNA of the women is 95 percent Native American. Spanish men and Native American women created a new population--confirming the recorded history of the region.
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The pattern of sexual exploitation by a dominant group seen in the preceding examples is not at all unusual in the human genetic record, says Reich’s frequent collaborator, Nick Patterson, a senior research scientist at the Broad Institute of MIT and Harvard. The Icelandic sagas record that the exiles who settled that island raided Scotland and Ireland, kidnapping Celtic women. And the genes corroborate this account. The mitochondrial DNA of the women is Celtic, the Y-chromosomes are Nordic
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Fortunately, the science of the human past has progressed in these other areas no less than in the field of genetics. Innovations in archaeological analysis have had a profound impact
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After the fall of the Roman empire, “you get this layer called ‘dark earth’” in the archaeological stratigraphy, he says. “People thought the empire fell and the cities turned into garden [plots]. That is how dark earth was understood up until about five years ago,
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“In the Roman excavations,” says McCormick, “there were pots and stone buildings and columns.” But then suddenly you get a layer of nothing but dark, humus-looking soil. What actually happened, Galinié and others have found, is that people shifted to organic building materials. “They had thatched roofs and wooden houses, they didn’t have Roman garbage removal, and they just dumped the ashes and charcoal from their hearths out in the road and all of that compacted. It is extremely rich, extremely dense,