An international team of researchers analyzed ancient DNA from nearly 300 individuals in the Iberian Peninsula, covering more than 12,000 years, in two studies published today on . Current Biology and Science . The first study examined hunter-gatherers and the first farmers living on Iberia between 13,000 and 6,000 years ago. The second concerned individuals in the region during all periods of time over the last 8000 years. Together, the two documents greatly increase our knowledge of the history of the population of this unique region.
The Iberian Peninsula has long been thought of as a forerunner in the history of the European population, due to its unique climate and its position at the western end of the continent. During the last ice age, Iberia remained relatively warm, allowing plants and animals ̵
A man and a woman buried side by side on the site of the Bronze Age of Castillejo de Bonete in Spain had several genetic ancestors. ( Luis Benítez de Lugo Enrich and José Luis Fuentes Sánchez / Oppida )
The Iberian hunter-gatherers show two ancient Paleolithic lineages
For the map in Current Biology, led by researchers from the Max Planck Institute for the Science of Human History, the researchers analyzed 11 hunter-gatherers and Neolithic individuals from the Iberian Peninsula. The oldest individuals recently analyzed are around 12,000 years old and were recovered by Balma Guilanyà in Spain.
Excavation work underway at the Balma Guilanyà site. ( CEPAP-UAB )
Previous evidence had shown that, after the end of the last ice age, western and central Europe was dominated by hunter-gatherers with ancestors associated with about 14,000- one-year-old individual in Villabruna, Italy. It is thought that Italy was a potential refuge for humans during the last ice age, such as Iberia. The ancestry linked to Villabruna largely replaced the previous origins in western and central Europe relating to individuals of 19,000-15,000 years associated with what is known as the Magdalenian cultural complex.
It is interesting to note that the results of the current study show that both lineages were present in Iberian individuals dating back to 19,000 years ago. "We can confirm the survival of a further Paleolithic lineage dating back to the late Ice Age in Iberia," says Wolfgang Haak of the Max Planck Institute for the Science of Human History, senior author of the study. "This confirms the role of the Iberian peninsula as a refuge during the last glacial peak, not only for its fauna and flora, but also for human populations."
Prehistoric hunter-gatherers. ( CC0 )
This suggests that, far from being replaced by individuals linked to Villabruna after the last ice age, hunter-gatherers in Iberia actually already had origins from Magdaleniano and Villabruna – related sources. The discovery suggests an early connection between two potential refugees, resulting in a genetic origin that survived in later Iberian hunter-gatherers.
"The hunter-gatherers of the Iberian Peninsula bring a mix of two types of older genetic ancestors: one that dates back to the Ice Age and was once maximized in individuals attributed to Magdalenian culture and another that is found everywhere in Western Europe and central and had replaced the Magdalenian lineage during the first Holocene anywhere but the Iberian peninsula ", explains Vanessa Villalba-Mouco of the Max Planck Institute for the Science of Human History, the first author of the study.
Researchers hope that ongoing efforts to decipher the genetic structure of late hunter-gatherer groups across Europe will help better understand Europe's past and, in particular, assimilation of a Neolithic lifestyle determined by the expansion of farmers from the Near East during the Holocene.
The ancient DNA of individuals in the last 8000 years helps to clarify the history and prehistory of the Iberian Peninsula
The document published in Science focuses on slightly later time periods, and traces the history of the Iberia population in the last 8000 years by analyzing ancient DNA from a huge number of individuals. The study, conducted by Harvard Medical School and the Broad Institute and including Haak and Villalba-Mouco, analyzed 271 ancient Iberians of the Mesolithic, Neolithic, Copper Age, Bronze Age, and Iron Age and historical periods. The large number of individuals allowed the team to make more detailed inferences about each time period than before.
These two skeletons in La Braña, in the north-west of Spain, belonged to brothers with dark hair and blue eyes who lived 8,000 years ago and who were closely related to the hunter-gatherers of the Central Europe. ( Julio Manuel Vida Encinas )
The researchers found that during the transition to a sedentary peasant lifestyle, hunter-gatherers in Iberia subtly contributed to the genetic composition of farmers just arrived from the Near East. "We can see that there must have been a local mixture because even the Iberian peasants carry this dual signature of unique hunter-gatherer lineage for Iberia," explains Villalba-Mouco.
Between 2500-2000 BC, researchers observed the replacement of 40% of the lineage of Iberia and almost 100% of its Y chromosomes by people with ancestors of the Pontic steppe, a region in what is now the Ukraine and Russia. It is interesting to note that the results show that in the Iron Age "the steppe ancestry" had spread not only in the Indo-European language regions of Iberia, but also in those of the non-Spanish language Indo-European, like the region inhabited by the Basque Country. The researchers' analysis suggests that the current Basques are more like a typical Iberian population of the Iron Age, including the influx of "steppe bloodlines", but that they were not influenced by subsequent contributions genetics that have affected the rest of Iberia. This suggests that Basque speakers were equally genetically influenced as other groups from the arrival of the steppe populations, but still maintained their language. Only after that time did they become relatively genetically isolated from the rest of the Iberian peninsula.
Olentzero in Beasain. Gipuzkoa, Basque Country. (Izurutuza / CC BY SA 3.0 )
Furthermore, the researchers examined the historical periods, including the times when Greek and later Roman settlements existed in Iberia. The researchers found that starting at least from the Roman period, the ancestry of the peninsula was transformed by gene flow from North Africa and the eastern Mediterranean. They discovered that the Greek and Roman settlements tended to be multi-ethnic, with individuals coming from the central and eastern Mediterranean and North Africa, as well as local ones, and that these interactions had lasting demographic and cultural effects.
"Beyond the specific insights on Iberia, this study serves as a model for how an ancient high resolution transept DNA that continues into historical periods can be used to provide a detailed description of the formation of current populations," explains Haak. "We hope that the future use of similar strategies will provide equally valuable insights in other regions of the world."
Top Image: The farmers of the Pontic steppe drastically transformed the Iberian DNA 4500 years ago. Source: Out of the Woods
The article, originally titled & # 39; The only diversity in the genetic history of the Iberian peninsula revealed by dual studies & # 39; w as published for the first time in Science Daily.
Source: Max Planck Institute for the Science of Human History. "The unique diversity of the genetic history of the Iberian peninsula revealed by dual studies." ScienceDaily. ScienceDaily, March 14, 2019. www.sciencedaily.com/releases/2019/03/190314151551.htm
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