Six centuries without changes in the DNA of the Iberians

BarcelonaThe Romans left a profound mark on the Iberian Peninsula, visible in Latin, Roman law, aqueducts, bridges, amphitheaters, and triumphal arches. Thanks to genetics, we now know that their arrival also changed the population's DNA. A study led by researchers from the Autonomous University of Barcelona (UAB) and published in the journal iScience has obtained the most complete and accurate image to date of the history and genetic evolution of the Iberian peoples who inhabited the northeast of the Iberian Peninsula from the beginning of the Iron Age to the Roman conquest, between 2,700 and 2,100 years ago.

Genetic information can tell us many things, from the origin of the Iberians to mobility dynamics or the openness of society at the time to other peoples. It is not easy to trace this culture because its language has not yet been deciphered, nor are there many human remains because they cremated their dead. All the information from the study was obtained from the analysis of the genomes of 54 infants buried in domestic structures and productive areas of three sites: els Vilars, in Arbeca (Lleida), belonging to the Ilergetes people; Sant Miquel d’Olèrdola, in Olèrdola (Penedès), of the Cossetans people, and El Camp de les Lloses, in Tona (Barcelona), of the Ausetans group.

The steppe dwellers were the ones who caused the most radical change. In a few centuries, Cristina Santos, a researcher in biological anthropology at the UAB who led the study, explains that there is great genetic continuity between the Bronze and Iron Ages. “We see great genetic continuity, that the population changed much less than we had imagined based on the archaeological evidence of Mediterranean cultures found in these peoples, such as those of the Phoenicians, Greeks, and Carthaginians. These influences occurred, but very gradually,” she says.

All analyzed individuals had the genetic profile established by the migratory waves that arrived in the Iberian Peninsula before and during the Bronze Age: the hunter-gatherers of Western Europe, the farmers from the Anatolia region (modern-day Turkey) – who led the Neolithic Revolution in Europe, where they spread rapidly – and the Steppe people or Yamnaya, who arrived about 4,500 or 5,000 years ago originating from the Pontic Steppes, north of the Black Sea and the Caspian Sea, between modern-day Ukraine and Russia.

No changes after the Steppe people

The steppe dwellers were the ones who brought about the most radical change. In a few centuries, practically 100% of the autochthonous male lineages (the Y chromosome) were replaced by the steppe lineage (R1b)very precise information about the remains of the infantsThis isolation from Iberian society was not exactly the same everywhere. Settlements close to the sea were a little more permeable, because they had more contact with Greeks, Phoenicians, and Carthaginians who stopped there on their trade routes. Els Vilars show a low degree of miscegenation, while the coastal site of Sant Miquel d'Olèrdola, connected to the sea by streams and close to the ports of Sitges and Darró, shows more external genetic contributions. For example, a newborn with the mitochondrial haplogroup M1, of North African origin, has been found there. Researchers suggest that it could have had Carthaginian or Punic ancestry.

The real shake-up came with the Romans and the Second Punic War, which led to many social changes. The clearest example is found at the Camp de les Lloses archaeological site, where the inhabitants worked on the construction of the road of the proconsul Mani Sergi (c.110 BC), which communicated the Catalan coast with the interior, crossing Osona. In this settlement, components connected with Mediterranean and North African populations are detected much more often. There is continuity in maternal lineages and, everything suggests, that the changes occurred due to the union of local women with foreign men.

Our DNA stores everything

"Neither the genetic information of the Neolithic people, nor that of the steppe people, nor that of the Iberian people is erased. It continues to be part of our DNA, to which contributions from other peoples who arrived later in the Iberian Peninsula have also been added," concludes Santos, who is cautious about the results of this study because only three settlements in the northeastern Iberian Peninsula could be studied. "If we analyzed the DNA of the sites in the south of the Peninsula, perhaps the information would be different," he assures.

A couple of years ago, the same university already obtained very precise information about the remains of children, which have been the great source of knowledge for this research. In that study, the moment of birth and death of these newborns could be accurately identified. For 22 of the 54 newborns studied, the team has been able to recover more than 20,000 genetic variants (SNPs) from the entire genome, in addition to the almost complete mitochondrial genome, while for 9 more the mitochondrial genome has been recovered.

The analyses have been carried out in the ancient DNA laboratory of the Faculty of Biosciences of the UAB. Researchers from the universities of Granada, Lleida, Coimbra (Portugal), Copenhagen (Denmark), and Brown (United States), from Adelaide (Australia), as well as from the Museum of Archaeology of Catalonia, the El Camp de les Lloses Museum, have also participated in the research.