NEW YORK – By analyzing DNA from hundreds of individuals going back some 7,000 years, researchers have retraced population patterns at several sites from modern-day France, identifying ancient farmer, hunter-gatherer, and other interactions that tie in with genetic and cultural changes that took place in other parts of Europe from the Mesolithic Period to the Iron Age.
The study, published in the Proceedings of the National Academy of Sciences on Monday, "complements the genomic history of western Europe for this broad period by supplying a large genetic transect of three regions of France," University of Paris researchers Melanie Pruvost, Eva-Maria Geigl, and Thierry Grange, the study's co-corresponding authors, and their colleagues wrote.
"Parental lineages and genomic data both revealed demographic patterns in France from the Neolithic and Bronze Age transitions consistent with neighboring regions, first with a migration wave of Anatolian farmers followed by varying degrees of admixture with autochthonous hunter-gatherers, and then substantial gene flow from individuals deriving part of their ancestry from the Pontic steppe at the onset of the Bronze Age," they noted.
Using targeted SNP testing, Y chromosome marker analyses, mitochondrial genome sequencing, and low-coverage whole-genome sequencing, the researchers profiled a total of 243 ancient individuals from dozens of archeological sites in northern, eastern, and southern France, teasing out the age of the samples based on their archeological context in combination with radiocarbon dating on a subset of 40 samples.
By analyzing the sequence data alongside genetic data for ancient and modern individuals profiled from across Eurasia, the team uncovered interactions between local hunter-gatherers and incoming individuals from an Anatolian farmer group during the Neolithic — part of a broader transition from hunter-gatherer to agriculture-based lifestyles in western Europe.
Compared to hunter-gatherer populations present at earlier time points, the authors noted that ancient individuals sampled from the early and middle Neolithic time points "share more affinity with present-day southern Europeans, and their genetic variation is encompassed within that of contemporaneous European populations."
Among other notable population features, the team saw ongoing hunter-gatherer ancestry stemming from a "Magdalenian" group that is best known in Spain's Iberian Peninsula. They detected this Magdalenian ancestry in hunter-gatherers sampled from sites in western and central France, including hunter-gatherer groups that met and mixed with Anatolian farmers.
"Our genomic data obtained from three Mesolithic individuals from western France show that the late survival of the Upper Paleolithic Magdalenian-associated ancestry … was not restricted to the Iberian Peninsula," the authors reported. "This finding expands the region where this ancestry is found and raises the question of where this admixture occurred."
In the lead-up to the Bronze Age, meanwhile, when a cultural group called the Bell Beaker complex became more prominent in parts of Europe, the investigators' analyses pointed to an uptick in ancestry from the Pontic steppe region. This ancestry became more prevalent across the Bronze Age and was followed by a span of relative population genetic stability stretching into the Iron Age.
"An important outcome of our study is the genetic continuity between Bronze and Iron Age individuals of France but with less heterogeneity between individuals from the Iron Age," the authors concluded. "In such a context, tracing migrations from one part of Europe to the other becomes more challenging and will require a deeper temporal and geographical resolution."
The team also delved into data at some 73 genetic loci in 149 of the ancient samples to search for signs of selection in parts of the genome related to everything from skin and eye coloring to innate immunity, inflammation, and diet in the Mesolithic hunter-gatherers and Anatolian farmers from the Neolithic relative to present-day populations in France.
"The study of a selection of nuclear markers revealed differences between Neolithic people and present-day Europeans," the authors wrote, noting that "[d]erived allele frequencies indicate selection on loci involved in pigmentation, diet, and immunity that are consistent with adaptation to high latitudes and changes in diet."