What is it about?

March 28th, 2019 0 Three UV experts participate in the biggest research on the genomics history of the Peninsula Three UV experts have taken part in the biggest research on the genomics history of the Iberian Peninsula that has just been published in the 'Science' journal. Yolanda Carrión, Oreto García Puchol and Agustín Díez-Castillo participated in this project, which reveals an invasion of steppe descendants that replaced almost all men 4,000 years ago. Project (HAR2015-68962: EVOLPAST) can be checked out here. Yolanda Carrión, Oreto García Puchol and Agustín Díez-Castillo are researchers from the Department of Prehistory, Archaeology and Ancient History at the Faculty of Geography and History of the Universitat de València. The international research, co-directed by the Institute of Evolutionary Biology and Harvard University, covers the last 8,000 years of history of the peninsula. Supported by the National Institute of Health (USA) and la Caixa, the study has revealed that the current Basque population presents the typical genetics of Iberia in the Iron Age. The research has come up with a genetic map of the peninsula. The genomes of 271 peninsular inhabitants from different eras have been analysed and contrasted with the data collected in previous research of other 1,107 old individuals and 2,862 modern individuals. The results show an unprecedented image of the transformation of Iberian population throughout history and prehistory. Replacement of male population in the Bronze Age The arrival of descendant groups of shepherds from Eastern Europe steppes 4,000 to 4,500 years ago meant the replacement of approximately 40% of total population and almost 100% of men. ‘The genetic results are pretty clears in this respect. Progressively, during a period of around 400 years, the lineages of Y chromosome that were present until the Chalcolithic were almost completely substituted by a lineage, the R1b-M269, from steppe origins’, explains researcher Carles Lalueza-Fox, from the Institute of Evolutionary Biology (centre run by the CSIC and the Universitat Pompeu Fabra). ‘Although this was clearly a dramatic process, the genetic data can’t actually tell us what caused it’, says David Reich, main researcher at Harvard Medical School and co-responsible of the study. ‘It would be wrong to claim local population was displaced, since there is no evidence of general violence in that period’, adds Íñigo Olalde, Harvard University researcher. An alternative explanation would be that Iberian women preferred the newcomers from central Europe in a context of ‘high social stratification’, says Lalueza-Fox. The research team highlights the genetic data won’t reveal the whole story. ‘Evidence of other fields, like archaeology and anthropology, must also contribute to these findings in order to better understand what propeled this genetic pattern’, claims Reich. As an example of this replacement phenomenon, the study documents a tomb that was found in a site of the Bronze Age (subsequent to the Chalcolithic) in the town of Castillejo del Bonete (Ciudad Real). Out of the two indivuals found in the burial site, the man presents steppe ancestry and the woman is genetically similar to the Iberians of the Chalcolithic. Basque genetics Another of the main conclusions of the study is that Basque genetic has barely changed since the Iron Age (3,000 years ago). Contrary to what some theories supported, saying Basque people were descendats of Mesolothic hunters or the first farmers that lived in the Iberian Peninsula, the results of this research show the genetic influence of the steppe also arrived to the Basque Country (in fact, they have one of the highest Y R1b chromosome frequencies). However, they barely present influences of later migrations like the Romans, the Greeks or the Muslims, since they were isolated from them. ‘Now there’s the belief that Indo-European languages spread throughout Europe thanks to the descendants of the steppe people. In this research, we repair the complex genetic kaleidoscope of the Iberian Peninsula, where we find primitive languages like the Indo-European Celtiberian or non-Indo-European languages like Iberian, as well as Basque, the only pre-Indo-European language of Europe that’s spoken nowadays. Our findings show Celtiberians have a major genetic component of steppe population than Iberians, although in any case there is a clear dissociation between language and ancestrality’, says Lalueza-Fox. African contacts The distribution of African genetics to the Peninsula is actually more ancient than what was documented until now. The study confirms the presence in a site in Camino de las Yeseras (Madrid) of an individual coming from the north of Africa that lived there 4,000 years ago, as well as the grandson of an African emigrant in a site in Cadiz around the same period. Both indivuals had considerable proportions of sub-Saharan ancestrality. Nevertheless, these are occasional contacts that left little DNA profiling in Iberian populations of the Chalcolithic and the Bronze Age. Besides, the results show there was a Nord-African gene flow in the south-east of the Peninsula during the Punic and the Roman periods, long before the arrival of the Muslims to the Peninsula in the 8th Century. Romans, Greeks, Phoenicians, Visogoths and Muslims The analysis of the genetic map shows deep changes in population in the Iberian Peninsula during the more recent historical periods. ‘For the first time, we have documented the genetic impact of the biggest events of the history of the peninsula. The results shows that, when the Middle Age started, at least a quarter of Iberian ancestrality had already been replaced by new flows of population coming from the eastern Mediterranean (Romans, Greeks and Phoenicians). This demonstrates migrations during this period still had a huge impact in the formation of Mediterranean population’ says Íñigo Olalde. One of the examples of this phenomenon is the Greek colony of Empúries, in the north-east of the peninsula, founded around 600 years before our age and the later Roman period. The 24 individuals that have been analysed can be divided into two groups of different genetic ancestry: one for individuals with a typical Greek ancestrality and another one for population genetically indistinguisable from the Iberians of the nearest village, Ullastret. ‘The article also analyses the arrival of the Visogoths and the Muslims to the Peninsula. Among the first ones, two individuals have been located at the site of Pla de l’Horta (Girona) with a clear eastern Europe ancestrality and a typical Asian mitochondrial DNA. From the Islamic period, individuals from Granada, Valencia, Castellón and Vinarós have been analysed. They show a North-African component close to a 50%, higher than the residual 5% observed in current Iberian population. In this case, this was an ancestrality almost eliminated during the Reconquest and the later expulsion of the Moriscos’ says Lalueza-Fox. Structure of Mesolithic Iberia population This research, together with another one published on the same day in Current Biology, identifies the presence of an spatial and temporary genetic structure in the harvester hunters of the Iberian Peninsula during the Mesolithic (around 8,000 years ago). In the north-east, Mesolithic hunters that lived a few centuries before the arrival of the first farmers show a genetic similarity with the harvester hunters from the centre of Europe. That ancestrality wasn’t present in the ealier harvester hunters of the same region or the contemporary harvester hunters of the south-east of Iberia at the end of the Mesolithic. The research has been supported by la Caixa, FEDER-MINECO (BFU2015-64699-1118P), the National Institutes of Health ((grant GM100233), the Paul G. Allen Family Foundation and the Howard Hughes Medical Institute, among others.

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Why is it important?

The research has come up with a genetic map of the peninsula. The genomes of 271 peninsular inhabitants from different eras have been analysed and contrasted with the data collected in previous research of other 1,107 old individuals and 2,862 modern individuals. The results show an unprecedented image of the transformation of Iberian population throughout history and prehistory.

Perspectives

Writing this article was a great pleasure as it has co-authors with whom I have had long standing collaborations. This article also lead to map the genome of almost 300 individuals that will be key for new research in the area.

Dr. Agustín Angel Diez Castillo
Universitat de Valencia

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This page is a summary of: The genomic history of the Iberian Peninsula over the past 8000 years, Science, March 2019, American Association for the Advancement of Science, DOI: 10.1126/science.aav4040.
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