Where modern Europeans came from

In the modern era, Europe has been defined as the western part of the Eurasian landmass. All of what is now called Europe was once populated by hunter-gatherers who lived based on what they could hunt, pick or dig up from the soil.

At some point, however, Europeans began farming, as Neolithic people swept west and north across Europe from what is now called the Middle East.

Later, another shift occurred during the transition to the Early Bronze Age, when farming based on domesticated plants and animals became the norm, and several technological innovations in agriculture also occurred.

Now palaeogenomic analyses of more than 1,600 ancient genomes from all over Europe and western Asia show that the transition from one age to another was not merely the result of exchanging technologies and ideas.

This transition affected the entire population of Europe: in some places, the population was completely replaced by migrants from the east, and in other places migrants assimilated with existing populations somewhat.

“Solely based on archaeological observations, one can see a shift from hunter-gathering to farming to Early Bronze Age cultures, but this does not reveal whether the people who lived during the different cultural eras were actually different or belonged to a continuous population. This study thoroughly answers this question based on the most extensive ancient DNA data set ever,” 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 more than 1,600 ancient genomes

The researchers shotgun-sequenced 317 primarily Mesolithic and Neolithic genomes, and the data set also included 1,300 previously published sequenced genomes from the period 4,000 to 12,000 years ago.

The genome sequencing was performed on ancient DNA extracted from teeth or petrous bones from skeletons from all over Eurasia. The researchers then filled in the gaps in the patchy ancient genomes by approximating the rest of the genetic code.

Sequencing of highly fragmented ancient DNA rarely enables the total genome of an individual to be determined, but based on the DNA structure of many thousands of genomes from currently living people, the researchers could fill in the gaps in their data, thereby creating a data set of more than 1,600 complete ancient genomes.

“With 1,600 ancient genomes at hand, we can analyse with a precision and resolution that has not been possible before in this research field. This provides far better understanding of our genetic origins than previously,” says Morten Allentoft.

People from the Middle East replaced hunter-gatherers

The analysis revealed many exciting aspects about the history of Europeans.

The researchers followed how Neolithic people brought agriculture to Europe beginning about 10,000 years ago and replaced the hunter-gatherers.

The DNA analysis also shows very clearly that the Neolithic people from the Middle East did not just learn from the hunter-gatherers who had lived in Europe but definitely replaced them.

This massive population turnover is very evident throughout Europe, although there were also small differences.

The original hunter-gatherers in parts of southern Europe were more frequently genetically assimilated into the arriving Neolithic people.

This happened to a lesser extent in northern Europe, with the Neolithic people replacing the hunter-gatherers.

Some of these observations were partly known from previous studies but there were also surprises.

“For the first time, we have identified an invisible genomic boundary extending from the Black Sea to the Baltic: a great divide. The entire population west of this boundary was replaced by incoming Neolithic farmers, but we do not know why nothing happened east of the great divide, where hunter-gatherers remained. Perhaps they had more developed cultures and were better able to resist these migrants from the south,” explains Morten Allentoft.

Population of Denmark turned over shockingly fast

Further, the researchers found a wider difference in ancestry when the populations were replaced.

In southern and central Europe, the population turned over at least 1,000 years earlier than in what is now called Denmark, but when it finally occurred in Denmark the transition happened very rapidly, and the hunter-gatherers disappeared within a few generations and were replaced by Neolithic people.

“Again, we do not know why this happened and can only state that it did happen. Genocide may have been a factor, or the original people may have migrated. We do not know,” notes Morten Allentoft.

He also emphasises that the research shows who populated Denmark and the rest of northern Europe once the hunter-gatherers disappeared.

People mainly had DNA from the Middle East but also some hunter-gatherer DNA that did not originate from Denmark but from further south in Europe, where the Neolithic people assimilated it on the journey north.

“We found a small degree of mixing with local hunter-gatherer DNA, but the situation really resembles a near-complete replacement of the population. This provides important new insight on the transition from the Mesolithic hunter-gatherer culture in Europe to the Neolithic Age,” says Morten Allentoft.

Advanced migrants from the east replaced Neolithic people

The study also elucidates what happened in Europe in connection with the next major population turnover about 5,000 years ago, when the nomadic Yamnaya people from the Pontic Steppe (now Ukraine, southwestern Russia and western Kazakhstan) travelled west.

The Yamnaya were more advanced than the Neolithic people and had carts and oxen, which made them much more mobile.

The researchers found that the population in southern Europe was replaced through partial mixing of Neolithic people with the Yamnaya versus mostly nearly complete replacement of one people with another in northern Europe – including in what is now Denmark.

The researchers also found that the great divide broke down at this time, and the populations became much more genetically homogeneous between east and west.

The study shows that Yamnaya first mixed with Neolithic people who lived in eastern Europe, and these mixed people then spread very fast across the whole of Europe and still comprise most of the DNA in present-day Europeans.

“Europe does not have people with exclusively Yamnaya DNA, because everyone is some kind of mixture. But the more Yamnaya DNA people have, the taller and more robust they are. This is also the case today, with people in northern Europe having more Yamnaya ancestry than people in southern Europe,” explains Morten Allentoft.

Provides unique insight into the European past

The Yamnaya are therefore absolutely central to understanding European prehistory, and the new study also reveals the genetic ancestry of the Yamnaya.

The genetic analysis broadly characterises the Yamnaya as a mix between Caucasus hunter-gatherers and eastern hunter-gatherers from the Pontic Steppe.

“All these findings provide new insight into our common European prehistory and understanding of where we all come from. There was no written language in this deep prehistoric past, so DNA is the only way we can learn about the origin and the fate of these early people. The data presented in this study also laid the foundation for several accompanying studies, in which we identified the importance of genetic origin in determining the risk of developing various diseases,” concludes Morten Allentoft.