New light shed on the Stone Age ‘invisible wall’
Archaeological finds have long pointed to the existence of a kind of barrier, a ‘great divide’ that for long periods stretched up through Europe from the Black Sea in the south to the Baltic Sea region and the Baltic countries during the Stone Age . Analyses of 1600 prehistoric genomes has now shed new light on this invisible wall between different peoples.
During the Stone Age, a kind of invisible wall ran through Europe – a culturally determined dividing line between different peoples who had somewhat different lifestyles, especially when it came to how they subsisted. This dividing line has occupied archaeologists for many years. What were the genetics of the different groups of people living to the east and west of this great divide?
“We were already well aware that such a dividing line existed during the Stone Age and knew that people east of this great divide remained hunters, fishers and gatherers, while those who lived to the west of it over time became pastoralists. That is, until a point in time during the Bronze Age, about 4000 years ago, when this sharp divide began to dissolve. What we did not know was whether these different groups differed genetically. And it turns out that they did according to our analyses of these prehistoric teeth and bone fragments,” says Kristian Kristiansen, an archaeologist at the University of Gothenburg and one of the researchers behind the article Population Genomics of Post Glacial Western Eurasia, which is one of four articles recently published in the journal Nature.
Imputation renders older DNA usable
The study contributes crucial new knowledge about the differences in the genetics of hunters, fishers and gatherers in the entire western part of Eurasia. The researchers began preparing the study over ten years ago, and even in the initial phase, it was clear that the oldest DNA samples, up to 11,000 years old, posed a major challenge. The DNA was extremely degraded, but as experience was gained and new technologies emerged when it comes to sampling and extracting DNA, the researchers were soon able to go further back in time with their investigations.
With the aid of imputation, an advanced form of mathematical modelling and based on the analysis of a very large number of modern genomes, the holes in incomplete prehistoric DNA profiles could be filled, rendering these profiles usable and reliable in a wide range of advanced statistical analyses.
Ample food
The researchers already knew about the main genetic traits of three major prehistoric migrations, but many questions remained unanswered. Who were these people? Where did they come from? And to what extent did they interbreed with the local population?
There have been previous theories to explain why the invisible wall through Europe arose. One of them was that people in the area east of this great divide did not engage in agriculture because the continental climate was not well-suited to it, which meant that they stuck to their way of life as hunters, fishers and gatherers.
The climate may have played a role, but the explanation is more complex than that according to Kristian Kristiansen, and points to the culture of the hunters, fishers and gatherers east of the great divide.
“These were very well-organised and sophisticated societies that also included elites such as a warrior class. They had learned how to make pottery and possessed knowledge about food preservation that allowed them to store food. But there was also enough food in the form of fish in the rivers and lakes and game in the forests, so there were no compelling reasons for them to change their lifestyle. In my opinion, that is the main reason why this great divide persisted between these different groups of people. That is, until a new warrior elite west of the divide – from an area between Scandinavia and the Urals – embarked on conquests with horse-drawn chariots about 4000 years ago.
These were the contemporary equivalent of modern-day tanks, and the hunters, fishers and gatherers had no chance of defending themselves against them,” says Kristiansen.
Genetic mix
Scientists can now show that the Great Divide arose long before the Neolithic, at a time when the peoples on both sides of this line were hunter-gatherers. This discovery raises questions about why the divide existed, since the groups of people on both sides of it had similar lifestyles, and subsisted in the same way. Could the reasons have been cultural or trade-related, for example? This question cannot be answered as yet.
The study shows that the Yamnaya people emerged as a genetic mix between hunters, fishers and gatherers east of the great divide and the people from the Caucasus along the Don River. They lived on the Pontic steppe, now part of present-day Ukraine, southwest Russia and western Kazakhstan, and were the first nomads.
“They had ox-drawn wagons, covered like prairie wagons, and were able to move across the steppe with their animals. While they didn’t develop true agriculture, during their migrations from the Pontic steppe they learned to grow a bit of barley from the local people in eastern Hungary, north of the Carpathians. They took this knowledge with them when they began to migrate more actively towards northwest Europe and Scandinavia, which they reached about 4850 years ago,” says Kristian Kristiansen.
They spread at lightning speed
Their conquest took almost no time at all. The study shows that from the time the Yamnaya people became genetically mixed with people from the Corded Ware culture in Eastern Europe, it took only about 50 years until they had spread out along a distance of almost 900 kms, from the Netherlands to the Limfjord in north-west Denmark,” Kristiansen says.
“And everywhere they went they burned down forests to be enable their semi-agricultural lifestyle, with a few crops like barley and domesticated animals such as oxen and sheep.
The genetic mixing of the Yamnaya people with the Corded Ware people gave rise to the Single Grave culture in Denmark (which in Sweden is called the Battle Axe culture), and it is largely these people who are the closest ancestors of the Scandinavian peoples alive in Scandinavia and north-western Europe today. Their journey from the Pontic steppe to north-west Europe is mapped in the Nature article titled Population Genomics of Post Glacial Western Eurasia.
Contact:
Kristian Kristiansen, Phone: +46(0)704-18 57 67, e-mail: kristian.kristiansen@archaeology.gu.se
Four articles in Nature
Population Genomics of Postglacial Western Eurasia (Allentoft et al.)
The Selection Landscape and Genetic Legacy of Ancient Eurasians (Irving-Pease et al.)
100 Ancient Genomes Show Repeated Population Turnovers in Neolithic Age Denmark (Allentoft et al.)
Two of the articles in Nature are related to the research project RISE II, which is funded by the Bank of Sweden Tercentenary Foundation (RJ) and is a collaboration between the Department of Historical Studies at the University of Gothenburg, the University of Copenhagen, and the Lundbeck Foundation GeoGenetics Centre. The other two articles in Nature on the Stone Age use material from the long-standing collaboration between the University of Gothenburg and the University of Copenhagen in the research projects RISE I and RISE II. This was a collaboration that began in 2011.
