NEW YORK – A team from the University of Bordeaux, the Max Planck Institute for the Science of Human History, and elsewhere has described distinct local hunter-gatherer groups interacting with incoming farming populations during the Neolithic in different parts of France and Germany.
Such findings "highlight the complexity of the biological interactions during the Neolithic expansion by revealing major regional variations," senior and co-corresponding author Wolfgang Haak, a researcher at the Max Planck Institute, and his colleagues suggested.
For a study published in Science Advances on Friday, Haak's team focused on remains going back thousands of years from 101 individuals from a dozen sites in present-day France and Germany. Their goal was to understand the population dynamics behind the Neolithic transition from hunter-gatherer to farming lifestyles in that region of western Europe.
"Our study aims to cover the key geographic region of modern-day France and neighboring regions in Germany to unravel the complexity and variability in cultural and biological interactions between human groups during the earliest stages of the Neolithic period," the authors wrote.
Broadly speaking, such cultural shifts have been linked to migrations of farming populations that moved out of the Middle East and into Europe along distinct Mediterranean and continental routes, they explained, though the details of these journeys and the local hunter-gatherer populations that they met and mixed with along the way are not as clearly documented.
"France is where the two streams of the Neolithic expansion overlapped, so understanding how these groups interacted would fill in a big piece of the puzzle," Haak said in a statement.
Using targeted capture-based sequencing, the team profiled mitochondrial genomes, along with some 1.2 million SNPs across the nuclear genome, in 98 Neolithic individuals and three individuals from the earlier Mesolithic period who were sampled from 12 sites in Germany and France. These data were then analyzed in combination with available sequence or SNP data for hundreds more ancient individuals and array-based SNP profiles for nearly 2,600 individuals from the present, representing populations from around the world.
Along with differences in the proportion of hunter-gatherer ancestry, depending on the sampling site, for example, the researchers saw distinct ancestry in central and southeastern regions of the area they studied compared to the ancestry found at Mediterranean sites and locations to the west. This prompted them to take a closer look at ancestry from eastern and western hunter-gatherers, and from a "Magdalenian" hunter-gatherer group that has been linked to the Iberian Peninsula, in the ancient individuals over space and time.
"Using the genetic substructure observed in European hunter-gatherers, we characterize diverse patterns of admixture in different regions, consistent with both routes of expansion," the authors reported, adding that "[e]arly western European farmers show a higher proportion of distinctly western hunter-gatherer ancestry compared to central-southeastern farmers."
The authors noted that the original source of some hunter-gatherer ancestry remains difficult to pin down due to the relatively low proportion of this ancestry in some Neolithic populations. Still, they suggested that the overall patterns being uncovered are consistent with complex population interactions that can vary considerably over time from one part of western Europe to the next.
"On the basis of our observations, we find that broad-brush models are increasingly less likely to reconcile the full spectrum and details of the farmer-forager interactions," the authors concluded, "and thus advocate the use of models with more regional focus in future studies."Â
In a related study published in the Proceedings of the National Academy of Sciences this week, researchers from the University of Paris and elsewhere took a look at population patterns across France over the past 7,000 years, including the Neolithic transition and a subsequent Bronze Age transition, using sequence data for more than 200 ancient individuals. Among other findings, they described "a migration wave of Anatolian farmers followed by varying degrees of admixture with autochthonous hunter-gatherers."
"Although widespread," the authors of that study wrote, "the process of admixture with hunter-gatherers shows regional variability and origins."