New genetic research has uncovered evidence of two almost-complete population turnovers in prehistoric Denmark over the past 7,300 years, indicating that two separate waves of mass murder likely occurred in the region during this time period, according to a study published in the journal Nature.

The first wave happened around 5,900 years ago, as incoming farmers associated with the Neolithic Funnel Beaker culture wiped out the existing Mesolithic hunter-gatherer population within just a few generations of arriving in Denmark. But the farmers’ dominance lasted only about 1,000 years before another wave of mass murder ensued, this time by migrants related to the Yamnaya pastoralists from the Eurasian steppe who largely replaced the Funnel Beaker farming culture around 4,850 years ago.

“This transition has previously been presented as peaceful. However, our study indicates the opposite,” said co-researcher Anne Birgitte Nielsen, a geology researcher and head of the Radiocarbon Dating Laboratory at Lund University in Sweden, in a statement. “In addition to violent death, it is likely that new pathogens from livestock finished off many gatherers.”

Examining 7,300 Years of Human Remains in Denmark

To investigate these population turnovers in Denmark, Nielsen and colleagues analyzed DNA sampled from 100 human skeletons spanning 7,300 years of Danish prehistory, from the Mesolithic, Neolithic and Early Bronze Age periods. The researchers also examined isotopes in the remains to determine individuals’ diets and places of origin over time.

They found that the earliest individuals belonged to Mesolithic hunter-gatherer cultures like Maglemose, Kongemose and Ertebølle, and were genetically similar to other Western European hunter-gatherers of that era. This population makeup remained relatively constant from around 10,500 to 5,900 years ago.

But that changed with the arrival of the Funnel Beaker farming culture, who had origins in Anatolia (modern-day Turkey) and brought agriculture to Denmark for the first time. Within just a few generations of the Neolithic farmers’ arrival, the existing Mesolithic hunter-gatherer population had been entirely replaced, according to the genetic analysis.

“A few individuals in the study who lived during the Neolithic-Mesolithic transition had hunter-gatherer roots but had adopted the culture and diet of the immigrant farmers,” explained University of Copenhagen evolutionary genomicist Hannes Schroeder, who was not directly involved in the research, in an interview. “Thus, individuals with hunter-gatherer ancestry persisted for decades and perhaps centuries after the arrival of farming groups in Denmark, although they have left only a minor genomic imprint on the population of the subsequent centuries.”

The Arrival of Steppe Pastoralists

The Neolithic Funnel Beaker farming culture dominated Denmark for about 1,000 years. But around 4,850 years ago, they were largely replaced by new incomers – a mixed population of both farmers and pastoralists from the Eurasian steppe known as the Single Grave culture.

These pastoralists brought the first domesticated animals to Scandinavia and were genetically associated with the Yamnaya, who kept livestock, used horses and carts for transportation, and buried their dead in single graves marked by mounds. The arrival of the Single Grave culture represented another near-total population turnover, according to the genetic analysis.

“Once the people behind the Single Grave culture arrived, there was also a rapid population turnover, with virtually no descendants from the predecessors,” said Nielsen. “In the study, the team noted that the people associated with the Single Grave culture had an ancestry profile more similar to present-day Danes.”

Similar genetic patterns showing two major population turnovers have been found in other parts of Scandinavia during the same timespan. “We don’t have as much DNA material from Sweden, but what DNA there is points to a similar course of events,” explained Nielsen. “In other words, many Swedes are to a great extent also descendants of these semi-nomads.”

Violence and Disease Likely Caused the Rapid Turnovers

While the two cultural shifts in Denmark’s prehistory have previously been considered peaceful transitions, the rapid and near-total replacement of genetic lineages after each wave of migration tells a different story, the researchers say.

“It is likely that violence, and new pathogens from livestock, finished off many gatherers and farmers in turn,” Nielsen stated.

Evidence from archaeological sites also supports the idea that bloody conflicts occurred during these periods of change. For example, the remains of the “Porsmose Man”, a Neolithic male found in a peat bog in Denmark dating to around 5,000 years ago, showed he had been murdered with two bone-tipped arrows shortly after the arrival of Funnel Beaker farming culture.

Likewise, many of the Single Grave burials contain signs of trauma and violence. “Multiple individuals show traces of healed and unhealed cranial trauma, suggesting interpersonal violence,” explained Schroeder. “So clearly there was conflict going on in that period.”

Besides direct violence, the introduction of agriculture likely also brought infectious diseases that took a toll on existing hunter-gatherer populations without resistance or immunity.

“Pathogens that can spread from livestock could have been an important driver of the changes seen in our genomic data,” said population geneticist Ashot Margaryan of the University of Copenhagen, another member of the research team, in an interview.

Implications for Understanding Population Change

These findings provide insight into how quickly and drastically populations can change over time. The near-total replacement of genetic lineages with each new wave of migration was surprising given the relatively short timespan involved, just a few hundred years between the Mesolithic hunter-gatherers, Neolithic farmers and Yamnaya pastoralists.

“Our study demonstrates that human populations can change dramatically within a very short space of time,” said Lundbeck Foundation Professor Eske Willerslev of the University of Cambridge, senior author on the paper, in a statement. “We see this pattern time and again over the course of human history and prehistory: intermixing and then replacement of genetic lineages.”

The research also highlights how migrations and population mixing during prehistory have shaped the genetic makeup of Northern Europeans. “In Denmark, the transition from hunter-gatherers to farmers and [then] to pastoralists shaped present-day Danes, both genetically and culturally,” said Nielsen.

Further studies incorporating ancient DNA from additional regions and time periods will help to reveal more about the scale of these ancient migrations and how these dynamic population changes affected societies across Europe and Asia in the distant past.

References

• Margaryan, A. et al. (2023). Two major shifts in the population history of Denmark associated with the introduction of agriculture. Nature. https://doi.org/10.1038/s41586-022-05679-0
• University of Copenhagen. (2023, January 10). Genetic study reveals two major population shifts in prehistoric Denmark. EurekAlert! https://www.eurekalert.org/news-releases/961839