With the help of human bone samples provided by Université de Montréal, a large international network of researchers delves into the genetic origins of ancient peoples.
In an ancient DNA study published today in the journal Nature, scientists and archaeologists from over 80 different institutions, including Université de Montréal, lift the veil on the genomic history of Southeastern Europe, a region that has so far been barely analyzed using genetic information from human skeletons. This is the second-largest ancient DNA study ever reported (the largest, reported simultaneously in Nature by many of the same authors, focuses on the prehistory of Northwestern Europe).
Starting around 8,500 years ago, agriculture spread into Europe from the southeast, accompanied by a movement of people from Anatolia. This study reports data from the genomes of 225 ancient people who lived both before and after this transition, and documents the interaction and mixing of these two genetically different groups of people. “Southeastern Europe was the beachhead in the spread of farming from Anatolia into Europe," said Songül Alpaslan-Roodenberg, a consulting anthropologist at Harvard Medical School who identified and sampled many of the skeletons. "This study is the first to provide a rich genetic characterization of this process by showing how the indigenous population interacted with incoming Asian immigrants at this extraordinary moment in the past.”
“In some places, hunter-gatherers and incoming farmers seem to have mixed very quickly,” added first author Iain Mathieson, a geneticist at the University of Pennsylvania, “but mostly the two groups remained isolated, at least for the first few hundred years. These hunter-gatherers had been living there for thousands of years, and it must have been quite a shock to have these new people show up – with a completely different lifestyle and appearance”.
'Thoroughly mixed' ancestry
“Three thousand years later, they were thoroughly mixed," said David Reich, a geneticist at Harvard Medical School, the Broad Institute of MIT and Harvard and the Howard Hughes Medical Institute who co-directed the study. Added Mathieson: “Some populations derived up to a quarter of their ancestry from hunter-gatherers.” In other parts of Europe, this mixing was marked by sex bias, with most of the hunter-gatherer ancestry contributed by men. But in the southeast, the pattern was different. “This shows that the mode of interaction between the two groups was different in different places, something we need to try to understand in the context of the archaeological evidence."
The new paper also dramatically increases the number of samples from the population of hunter-gatherers that inhabited Europe before the farmers. The study reports a particularly rich sampling of forty hunter gatherers and early farmers from six archaeological sites from the Iron Gates region, which straddles the border of present-day Romania and Serbia. The genetic results show that the region witnessed intensive interaction between hunter-gatherers and farmers. Out of four individuals from the site of Lepenski Vir, for example, two had entirely Anatolian farmer-related ancestry, fitting with isotope evidence that they were migrants from outside the Iron Gates region, while a third individual had a mixture of ancestries and consumed aquatic resources as expected if farmers were being integrated into hunter-gatherer groups or were adopting a hunter-gatherer lifestyle.
“These results reveal the relationship between migrations, admixture and subsistence in the this key region and show that even within early European farmers, individuals differed in their ancestry reflecting a dynamic mosaic of hunter-farmer interbreeding” said Ron Pinhasi, an anthropologist at the University of Vienna who co-directed the study.
A Canadian contribution
The new paper also includes genetic data from a Late Neolithic Globular Amphora burial site in Kierzkowo, northwestern Poland, obtained from bone fragments brought to Canada by Université de Montréal geneticist Damian Labuda when he emigrated from his native Poland in 1982. The DNA shows these humans had more hunter-gatherer-related ancestry than Middle Neolithic groups from central Europe, with no evidence of steppe-related ancestry, indicating that the cultural frontier was also a barrier to the flow of genes.
"It shows the genetic link between Late Neolithic Globular Amphora cultures to south-eastern Europe, where farming was established,'" said Labuda, a scientist in the pediatrics department of Montreal's CHU Sainte-Justine Research Center and co-author of a recent related study on Neolithic genome diversity and the spread of Indo-European languages.
Extreme inequality of wealth
Also in the new paper is reporting on ancient DNA from the people who lived at iconic archaeological sites such as Varna, one of the first places in the world where there is evidence of extreme wealth inequality, with one individual from whom the study obtained data buried with more gold than all other known burials of the period. “The DNA from the famous Varna burial is genetically similar to that of other early European farmers," said Johannes Krause, director of the Max Planck Institute, Jena, who led the work on Varna. "However, we also find one individual from Varna and several individuals at neighbouring sites in Bulgaria who had ancestry from the eastern European steppe. This is the earliest evidence of steppe ancestry this far west – two thousand years before the mass migration from the steppe that replaced more than half of the population of northern Europe.”
Concluded Reich: “These very large ancient DNA studies, involving intense collaboration between geneticists and archaeologists, make it possible to build up a rich picture of key periods of the past that could only be weakly glimpsed before. Studies on this scale represents a coming of age for the field of ancient DNA. I look forward to what we will learn when similar approaches are applied elsewhere in the world.”
This study was conducted by an international team of 117 archaeologists, anthropologists, and geneticists from 82 institutions across Europe, the United States and Canada.
About this study
"The genomic history of southeastern Europe," by Iain Mathieson and David Reich of the Department of Genetics of Harvard University, et al, was published in Nature, Feb. 21, 2018, doi:10.1038/nature25778. Support was provided by the Human Frontier Science Program, the German Research Foundation, the Irish Research Council, the U.S. National Science Foundation, the Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding, the Croatian Science Foundation, the European Research Council, the U.S. National Institutes of Health, the Howard Hughes Medical Institute and the Paul Allen Foundation.
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