Genetic markers link Stone Age farmers to modern Basques

Modern-day Basques are most closely related to Iberian Stone-Age farmers, not pre-agricultural groups as suggested by previous hypotheses, according to a new genome analysis conducted by an international team led by researchers from Uppsala University in Sweden.

The findings, published Monday in the journal Proceedings of the National Academy of Sciences (PNAS), reached that conclusion after analyzing DNA obtained from eight early Iberian farmers, the authors explained. In addition, they believe that their findings could also demonstrate that the practice of farming was brought to Iberia by people similar to those migrating to the northern and central parts of Europe, and those farmers mixed with local hunter-gatherer groups.

“The genetic variation observed in modern day Basques is significantly closer to the newly sequenced early farmers than to older Iberian hunter-gatherer samples,” Dr. Torsten Günther, one of the lead authors and a researcher in the Uppsala University Department of Ecology and Genetics, told redOrbit via email.

“Previous studies on such hunter-gatherers have already suggested that Basques are unlikely their direct descendants and that some mixing with other incoming groups would be required,” he added. “The surprising result was that these individuals were quite similar to modern day Basques. Parts of that early farmer population probably remained relatively isolated since then (which we can still see in the distinct culture and language of Basques) while other modern Iberians show signals of later historic events which makes them different from Basques.”

Iberian, European farmers share similar backgrounds

According to the researchers, most of the previous work investigating the transition from small, mobile hunter-gatherer groups to larger, more sedentary agricultural societies have focused on central and northern Europe. Far less is known about how this transition took place in Iberia, they added. As part of their research, the Uppsala-led team looked at the remains of eight people associated with archaeological remains from El Portalón cave in Spain.

El Portalón, which is located in the renowned anthropological site Atapuerca, is “a fantastic site with amazing preservation of artifact material,” study co-lead author Dr. Cristina Valdiosera of Uppsala University and La Trobe University said in a statement. “Every year we find human and animal bones and artifacts, including stone tools, ceramics, bone artifacts and metal objects.”

She said that the site is “like a detailed book of the last 10,000 years, providing a wonderful understanding of this period,” and added that “the preservation of organic remains is great and this has enabled us to study the genetic material complementing the archaeology.”

Thanks to the remains found there, Dr. Günther, Dr. Valdiosera and their colleagues were able to complete the first ever genome-wide sequence data from Iberian ancient farmers, and found that like those found in central and northern Europe, they originated due to expansion from the south then mixed with local hunter-gatherer groups, spreading farming through population expansions.

They also found that later farmers were more genetically similar to the original hunter-gatherers than their predecessors, and by comparing the El Portalón individuals to all modern populations in Spain, they discovered that they are genetically most similar to modern-day Basques. In short, the results show that Basques trace their ancestry to early farming groups from Iberia, according to lead investigator and Uppsala University professor Mattias Jakobsson.

Enabling a look at the genetic landscape of the distant past

The samples they analyzed, Dr. Günther told redOrbit, were about 4,000 to 5,000 years old. The Atapuerca site they were taken from is less than 100 kilometers from today’s Basque country– this allowed them to obtain an idea of the land’s genetic landscape from a few thousand years in the past.

“I think the most exciting signal is the admixture among early farmers and European hunter-gatherers,” he said. “Parts of all farmers’ genomes originate from hunter-gatherer communities they met on their way across Europe. Part of this mixing probably happened in the Balkan region since we see signals shared among farmers all across Europe.”

“We see, however, some local signals in later farmers, which means that Scandinavian farmers mixed with Scandinavian hunter-gatherers while Iberian farmers mixed with Iberian hunter-gatherers,” the Uppsala researcher noted. “The genomic data shows that this process continued over several millennia – in some parts of Europe longer than archaeological records of hunter-gatherer communities exist.”

“This work is part of our general research program utilizing ancient DNA to look into the human past,” Dr. Günther added. “Studying the genome from a single ancient individual, from whom we know when and where he or she lived, can sometimes give us so much more information than sequencing a number of modern individuals. Excavations in the El Portalon cave are continuing and we are expecting to analyze additional and older samples in the near future.”

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Image credit: Thinkstock

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