The Population Genomics of Postglacial Western Eurasia is one of the four Nature articles presenting the data and premise on which the four studies are based. Carles Lalueza-Fox, the lead researcher at the Institute of Evolutionary Biology (IBE), a joint center of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF), and also the director of the Museum of Natural Sciences of Barcelona (MCNB), has participated in this study.

"This work began with some Spanish archaeologists and the team from Denmark a few years ago, after publishing the first Mesolithic European genome, that of the man from La Braña in León. Now it has culminated in a much broader geographical and temporal framework that allows us to understand not only the migratory dynamics since the end of the Ice Age but also how these affect aspects of the health of present-day Europeans," comments Lalueza-Fox.

By analyzing a dataset of ancient DNA from 1600 genomes, much larger than previously available, the study demonstrated that genetic differences among ancient populations in Western Eurasia were substantially higher than previously estimated, and also much higher than those observed in current populations.

Illustration from  SayoStudio

This differentiation is partly due to the existence of an invisible genetic barrier across Europe. Archaeologists have long pointed out an apparent cultural barrier persisting from the Black Sea in the south to the Baltic Sea region in the north during the Mesolithic and Neolithic periods.

Within this geographic region, different cultural groups had different ways of life in terms of food acquisition, for example. Aligning archaeological knowledge with comprehensive ancient DNA analysis, the identification of this 'great divide' phenomenon plays a key role in the study.

"We knew that people east of the Great Divide maintained complex societies of hunters, fishers, and gatherers, while people in the west gradually became farmers until reaching a turning point in the Bronze Age, around 4000 years ago when the Great Divide began to recede. However, what we did not know was whether there was any genetic difference between the two groups living on each side. Now, analyses of ancient bones and teeth have revealed that there was," explains Professor Kristiansen, one of the co-authors of Population Genomics.

The Porsmose man from the Neolithic period, found in 1947 in Porsmose, Denmark. The Danish National Museum

In particular, this study provides new insights into genetic diversity among hunter-gatherer-fishers in Western Europe and east of this divide. These population structures were changing, and genetic diversity decreased when Anatolian farmers expanded into Europe during the Neolithic, and even more so when Yamnaya pastoralists dispersed across Europe around 5000 years ago.

The migration routes of Yamnaya pastoralists, whose lineage can be found in large proportions in present-day Europeans, are also traced in Population Genomics. Therefore, understanding the origin and dispersal of the Yamnaya is crucial for understanding the genetic origin of Europeans.

Genetically, the Yamnaya emerged as a mix of hunter-gatherer-fisher populations east of the Great Divide and people from the Caucasus living along the Don River. They inhabited the Pontic steppe in parts of what are now Ukraine, southwest Russia, and the Western Kazakhstan Region, and were the world's first nomads.

The new findings published by the team show that the Yamnaya mixed with people from a cultural group known as the Globular Amphora Culture and then dispersed rapidly across Europe. "It only took about 50 years to reach Bohemia and spread over almost 900 km between the Low Countries and the Limfjord in northwestern Denmark," explains Professor Kristiansen.

Illustration from SayoStudio

These migration events also had a genetic impact on various diseases in Europe, including type 2 diabetes and Alzheimer's disease. Similarly, the analysis of these ancient genomes provides new scientific evidence of ancient migrations explaining the prevalence of multiple sclerosis.

Overall, the four Nature articles demonstrate that collecting these genomes provides a precision tool capable of offering new perspectives on diseases when combined with current human DNA data and contributions from other research areas.