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Through the analysis of ancient DNA from more than 270 Iberians from different periods, an international team of researchers has reconstructed the 8,000-year genetic history of the Iberian Peninsula.
Scientists extracted ancient DNA from human fossils - mainly teeth - in order to compare these Iberian remains with 1,107 ancient and 2,862 modern individuals.
One of the most relevant conclusions is that there was a replacement of almost all the males of the Peninsula during the Bronze Age.
“We have not sampled the entire male population from that time, so we cannot say that 100% were replaced. However, as all the men sampled have the paternal lineage brought by new populations, and none have the local lineages previously present, we know that the replacement was practically total ”, Íñigo Olalde, a scientist at Harvard University (USA), explained to Sinc. ) and study co-leader.
Those populations, which They arrived between 2,500 BC. and 2,000 BC., they have steppe origin. When crossing the European continent they mixed with the local populations and when they arrived in the Iberian Peninsula they already had European ancestry. Nor did they have the same culture as the steppe populations of origin.
Various hypotheses about the invasion of the Bronze Age
The DNA reveals that the local male lineages disappeared and were replaced by this foreign lineage called R1b. Today R1b is still the majority lineage in the Iberian Peninsula. However, it is not known how it happened or what processes generated this genetic pattern.
“The genetic results are compatible with various explanations and more research in archeology and anthropology will be needed to understand the social processes that may have resulted in the loss of local paternal lineages. The most simplistic hypothesis is that these foreign men violently eliminated the locals and reproduced with the women. The problem with this hypothesis is that it does not fit with the archaeological record, since there is no evidence of generalized violence during that period ”, argues the scientist.
Another hypothesis is that these populations brought diseases for which local populations were not prepared, but there is also no evidence of infectious diseases affecting men and not women.
But nevertheless, local maternal lineages did remain.
The possibility they pose is the existence of a very strong social stratification by which foreign men had a much higher social status that local men (hereditary from father to son) and some much higher reproduction rates. That made the genetic footprint of the local man disappear after five centuries.
"These populations that enter the Peninsula were nomads and had a hierarchical and social structure that did not exist previously," explains Carles Lalueza-Fox, who is co-leading the study and is a researcher at the Institute of Evolutionary Biology (Centro Mixto del CSIC and Universidad Pompeu Fabra).
"We still do not know how it happened and our results encourage other disciplines to continue investigating in this fascinating period," emphasizes Olalde.
As an example of this replacement phenomenon, the study documents a tomb found in a Bronze Age site in the town of Castillejo del Bonete (Real city).
Of the two individuals found in the burial, the man presents ancestry from the steppe, while the woman is genetically similar to the Iberians before the late Neolithic. "It is representative of this substitution, a first-generation example of this type of contact," says Lalueza-Fox.
The peculiarities of the Basques
For years, thanks to genetic studies of current populations, it was known that the ancestry of the Basques was somewhat different from that of the rest of the populations that inhabit the Iberian Peninsula. This study provides an explanation of why the Basques have these differences.
“What we have found is that It is very similar to that of the populations of the Iberian Peninsula during the Iron Age (from 900 BC until the Roman conquest), while to explain the ancestry of the rest of the current populations, additional layers are needed that they incorporated during the last 2,000 years through the interaction with different peoples that came to the Peninsula, as Phoenicians, Carthaginians, Romans and Muslims.
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These towns affected the Basque area less in demographic terms, and so they have remained more similar to the populations of the Iron Age. "It also gives us a possible explanation of why of all the languages that were spoken in the Peninsula before the arrival of the Romans, only Basque has been maintained to this day”.
The rest of languages, both the non-Indo-European (for example the Iberian in the Mediterranean region) and the Indo-European Celtic languages in the central and western part of the Peninsula, they disappeared.
“In this study we show the complexities of the Iberian Peninsula, where there are Indo-European paleolanguages, such as Celtiberian, and non-Indo-European, such as Iberian, as well as Basque, which is the only pre-Indo-European language in Europe still spoken. Our results indicate a greater component of the steppes in Celtiberians than in Iberians; but in any case there is a certain dissociation between language and ancestry ”, adds Lalueza-Fox.
African migrations to the peninsula
The territory that today encompasses Spain and Portugal is at a crossroads between North Africa, Europe and the Mediterranean. According to scientists, it therefore offers an ideal opportunity to study the genetic impact of migration on the European continent, from the eastern Mediterranean and North Africa.
In the case of Africa, they have detected at least three periods in which there was a clear connection. “The first is during the Copper Age (between 3000 and 2000 BC), in which we have found a man buried in the Camino de las Yeseras site (San Fernando de Henares, Madrid) with 100% North African ancestry. that tells us that himself or all of his recent ancestors had that origin”Declares the scientist from Harvard University.
This guy who comes from Africa and ended up buried in Madrid, is the only one of all those who analyzed from the same site (some buried next to it) and from other sites from the same period (more than 100 individuals) that have this type of ancestors.
According to the researchers, this means that there was movement of people between North Africa and the Peninsula at this time, but which were probably sporadic events that did not significantly affect local populations in demographic terms.
The second contact occurred in Roman timesSince there are individuals from various sites in the province of Granada with a high percentage of North African descent. Finally, the already known impact during Muslim times.
“The interesting thing is that the current populations have much less North African descent than those of the Muslim era in the south of the Peninsula, and this is due to the expulsion of a large part of the Muslim population (officially Christian at the time of expulsion) and repopulation with populations from the center and north of the Peninsula ”, argues the expert.
The most recent history
Researchers have also studied the profound population changes in more recent times.
According to their findings, at the beginning of the Middle Ages at least a quarter of the Iberian ancestry had been replaced by new population flows from the eastern Mediterranean, Romans, Greeks and Phoenicians, which reveals that migrations during this period continued to have a great force in the formation of the Mediterranean population.
One of the examples of this phenomenon mentioned in the work is the Greek colony of Ampurias, in the northeast of the peninsula, between the years 600 before our era and the late Roman period. The 24 individuals analyzed are divided into two groups with different genetic inheritance: one made up of individuals with a typical Greek ancestry and the other made up of a population genetically indistinguishable from the Iberians from the nearby town of Ullastret.
Lalueza-Fox concludes: “When I was a child, I used to read old Iberian history books that were at home. I always wondered who these people really were, what mark they would have left on modern people and what all these movements meant in numerical terms. Now, for the first time, we can genetically study the remains of these people and integrate genetics not only with archeology and anthropology, but also with historical accounts.
Iñigo Olalde et al. ‘The genomic history of the Iberian Peninsula over the past 8000 years‘. Science. DOI: 0.1126 / science.aav1444.
Via: Eva Rodríguez in Sync