100 ancient skeletons reveal dramatic turnover of Denmark’s population

Tech Science 22. feb 2024 4 min Professor in evolutionary genomics and biodiversity Morten Erik Allentoft Written by Kristian Sjøgren

The entire population living in what is now Denmark was replaced twice prehistorically by people arriving from outside Scandinavia. A major study now reveals how this turnover took place and what it means for how ethnic Danes now look, live their lives and what they eat.

The most comprehensive analysis of ancient shotgun-sequenced genomes from the current territory of Denmark reveals in detail the genetic composition of the people living in Denmark over the past 10,000 years.

This shows that Denmark’s population has totally turned over twice, and that the Neolithic Stone Age people who brought farming to Denmark only lived there for 1,000 years before being replaced by Yamnaya-related immigrants with ancestry derived from the Pontic Steppe (now Ukraine, southwestern Russia and western Kazakhstan).

The people with Yamnaya ancestry replaced the Neolithic people about 5,000 years ago, and their genetics have made the present-day ethnic Danes, and other populations in northern Europe, among the tallest in the world, with many having light hair and blue eyes.

“Denmark is a unique country for this type of research because we have excavated and preserved an incredible number of ancient bones from people who lived here millennia ago. Archaeology has showed us how cultures have changed through millennia but the DNA obtained from the old bones can tell us how the population itself was replaced by new immigrants arriving from elsewhere in Eurasia,” explains lead author Morten Allentoft, Professor at Curtin University in Australia and the Globe Institute at the University of Copenhagen, Denmark.

The research has been published in Nature.

In-depth analysis of 100 skeletons

The researchers carried out the most extensive genome analysis ever of ancient bones from Denmark.

In addition to detailing the archaeological context and the geographical location of the bones, the researchers sequenced and analysed their genomes and performed radiocarbon dating and isotope analysis.

The massive multidisciplinary data set enabled the researchers to very precisely determine the physical and genetic characteristics of the people from whom the bones originated. They also very precisely dated these people and determined their diet through isotope analysis.

They then linked these data to the major cultural changes in Denmark during the past 10,000 years, from the turnover between the Maglemose, Kongemose and Ertebølle hunter-gatherer cultures to the transition from hunter-gathering to Neolithic farming and Early Bronze Age cultures.

The data provide a new and much more accurate picture of what has happened in Denmark for almost the whole time it has been populated.

Hunter-gatherer cultures were genetically similar

The ancient genomes show that the transitions between the hunter-gatherer cultures in Denmark were a shifts in culture only and not population turnovers.

The Maglemose culture population was genetically highly similar to the population of the Kongemose culture that replaced it and, again, similar to the Ertebølle culture millennia later.

The oldest genome also revealed that Denmark’s population has always had individuals with blue eyes but that the hunter-gatherers generally had darker skin than ethnic Danes have today.

“In this part of the study, we end the debate on whether the various hunter-gatherer cultures represent different populations migrating to Denmark. There was clearly genetic continuity during the whole Mesolithic Stone Age period. In addition, we also found that a child buried not far from where the Ertebølle Man was found was actually the Ertebølle Man’s son – thereby solving a 6,000-year-old paternity case,” says Morten Allentoft.

Population kept Neolithic people at bay for 1,000 years

Neolithic people with genetic ancestry from the Middle East replaced the original hunter-gatherer cultures throughout Europe, and genome analysis shows massive migration, which resulted in population mixing in some places and population turnover elsewhere.

Denmark underwent population turnover, but the DNA combined with the radiocarbon dating of the 100 skeletons reveals that the Neolithic immigration from the south happened 1,000 years later in Denmark. The hunter-gatherers in Denmark were therefore able to keep Neolithic people at bay for 1,000 years longer than in central Europe.

With the arrival of this new population from the south, its genetics eventually ended up lightening people’s skin, and once these migrants had established themselves in Denmark, the original hunter-gatherers were rapidly replaced, leaving only very minor genetic traces in the new population.

“Denmark may have had the most rapid transition from hunter-gatherers to the Neolithic Age in Europe. This was a dramatic transition with rapid turnover and involving far less genetic integration between the original population and the migrants than in southern Europe,” explains Morten Allentoft.

Neolithic population replaced rapidly

The Neolithic people, who had several millennia to establish themselves and thrive in the rest of Europe, had only 1,000 years as “Danes” before being replaced by the Yamnaya-related people with genetic origins from the Pontic Steppe.

The Yamnaya migrated into eastern Europe 5,000 years ago and mixed with some Neolithic people there.

The Corded Ware culture was founded in this mixed gene pool and these people rapidly spread across Europe, replacing the Neolithic populations.

In southern Europe, there was again more integration, with the researchers finding mixed ancestry in the genome.

In northern Europe, there was less mixing, and Denmark was the extreme with complete population replacement.

This dramatic shift from a Neolithic people with roots in what is now called the Middle East to a Corded Ware population with large quantities of Yamnaya ancestry happened about 5,000 years ago.

This event created the genome of modern ethnic Danes, which have had no major genetic changes since then.

The study also reveals that the Yamnaya DNA made the population taller and more robust.

“The Yamnaya were very tall, and populations with substantial Yamnaya ancestry in modern Europe are therefore taller. This applies strongly in northern Europe, which has more Yamnaya ancestry, but less strongly in southern Europe, which experienced greater genetic mixing between the local Neolithic people and the migrants with Yamnaya ancestry,” says Morten Allentoft.

New population changed Denmark’s landscape

In a final analysis, the researchers examined pollen from several sediments from ancient lakes, which showed how the vegetation in Denmark changed at the same time as the population changed from hunter-gathering to Neolithic farming and then to the Corded Ware culture.

The researchers found dramatic transitions, with major changes in land use and the landscape as the population was replaced.

Forests were burned to make way for fields with new types of grain.

“Everything matches, with the change in population leading to a shift from forest to farmland. Not only did the population turn over with the arrival of the various populations but land use and the landscape also changed,” concludes Morten Allentoft.

100 ancient genomes show repeated population turnovers in Neolithic Denmark” has been published in Nature. The Lundbeck Foundation GeoGenetics Centre – Globe Institute is supported by grants from the Lundbeck Foundation, the Wellcome Trust, the Carlsberg Foundation, the Danish National Research Foundation, the University of Copenhagen, Ferring Pharmaceuticals A/S and the Novo Nordisk Foundation.

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