The skeletons, which are between 7,500 and 3,500 years old, contain DNA that may be used to track migration waves from all over Europe.
It is not only the living who improve the subject of genetics: The DNA stored in our ancestors’ brittle bones can reveal a lot about our genetic past. Such is the case with a new genetic history of Europe, published today in Science by an international team of experts.
Writing Europe’s genetic history is like peering into the evolution of Western culture and being met with more questions than answers: Why do 45 percent of Europeans have the same haplogroup H mitochondrial DNA (DNA passed down through the maternal line)? What factors influence the dominance of one form of mitochondrial DNA over another? Is it possible to compare changes in an archaeological record to changes in a genetic record?
These questions might be answered by the new genetic history. Researchers from the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, the University of Mainz, the State Hermitage Museum in Halle (Germany), and the National Geographic Society’s Genographic Project derived mitochondrial DNA from the teeth and bones of 396 prehistoric skeletons to try to piece together Europe’s vast genetic history. These bones were discovered in a small, constricted area within the German state of Saxony-Anhalt, an area that had previously been identified to contain several usable skeletal samples in prior research.
“We retrieved DNA from almost 400 samples of skeletal individuals.” And we got unequivocal results that could be confirmed for 396 of them,” says ACAD’s Dr. Wolfgang Haak, one of the study’s primary authors. “Since DNA does not survive in all people, that was a tremendous success rate.”
The study featured a lot of previously unpublished data, including 10 times the amount of mitochondrial DNA studied in previous studies, making it the greatest assessment of ancient DNA to date. According to Haak, the researchers were able to compile a “gapless record…from the earliest farmers until the early Bronze Age” with such a massive amount of data.
Researchers were able to piece together this gapless genetic record by restricting their bone samples to a single location, which was one of the methods they used. Due to recent political history, the region of Saxony-Anhalt is exceptionally rich in historical bone samples: once the Berlin Wall was broken down, a large portion of former East Germany witnessed a massive infrastructural rehabilitation. Several old skeletons were discovered while digging new roads and highways, boosting the archeological record to the point that researchers now have access to a sample of specimens dating from 7,500 years ago to the current day. Furthermore, by limiting their search to specific geographic areas, the researchers were able to create a true transect of what happened over time in a single location, rather than a “patchy record of here and there,” as Haak puts it.
They were taken aback by what they discovered. Haak and his colleagues previously used ancient DNA to show that Central European lifestyles shifted from hunter-gatherers to farming around 5,500 BCE, shortly after a wave of migration from the Near East, as evidenced by a visible change in the genetic makeup when farming first appears in the archeological record. The genetic diversity of modern Europe, on the other hand, is far too complicated to be described just by this migration episode.
The problem that had baffled Haak and his colleagues–until now. The researchers were able to establish when alterations in mitochondrial DNA happened by obtaining samples from specimens that formed a complete timeline in Saxony-Anhalt. They discovered that while DNA patterns altered with the introduction of farming, they also changed thousands of years later, confirming their previous findings.
Researchers suggest that the genetic history of Europeans was influenced not just by a migration of farmers from the Near East, but also by subsequent migrations from cultures in the west (what is now the Iberian Peninsula) and east (what is now the Balkans) (what is now Latvia, Lithuania, the Czech Republic, and other modern Eastern European countries).
“We can demonstrate that the first genetic alteration occurred between hunter-gatherers and farmers using this genetic timeline,” Haak continues, “and it’s surprisingly consistent for roughly two thousand years when farming is well established.” “Then, towards the end of the Neolithic, we find a resurgence of early hunter-gatherer lineages,” says the author. Then, not long after, fresh impulses emerge, emanating from both the East and the West. There are now several additional elements that make up the majority of today’s diversity. We have almost everything in place that we see now by the time we reach the early Bronze Age.”
The authors’ theories on the origins of these waves of migration are based on the assumption that new cultural objects discovered in a certain place must have been carried there by people from far away. However, new technologies and artifacts do not, by themselves, imply that migrations have occurred to replenish the gene pool: as Haak points out, using an iPod does not make one particularly American, European, or anything else. Nonetheless, new tools and technologies appear to have gone hand in hand with genetic influxes, at least in ancient times, when migrants took old practices to their new countries.
