An international team of researchers has discovered the oldest human genome from southern Spain. This is the genome of a 23,000-year-old individual who lived in what was probably the warmest region of Europe at the peak of the last Ice Age. The discovery adds an important piece of the puzzle to the genetic history of Europe.
The genome was discovered in Cueva del Malalmuerzo in southern Spain, while the researchers were analysing ancient human DNA from several archaeological sites in Andalucía in southern Spain. The researchers also discovered 7,000 to 5,000-year-old genomes of early farmers from other well-known sites of southern Spain, such as Cueva de Ardales.
The study, led by Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany, was recently published in the journal Nature Ecology & Evolution.
Importance of Iberian Peninsula during the last Ice Age
According to the study, the Iberian Peninsula in Europe plays an important role in the reconstruction of human population history because it is a geographic cul-de-sac (has a dead-end) in the southwest of Europe, is considered a refuge during the last Ice Age with its drastic temperature fluctuations, and may have been one of the starting points for the recolonisation of Europe after the glacial maximum. The Last Glacial Maximum is the period when the continental ice sheets reached their maximum total mass during the last Ice Age. This happened around 24,000 to 18,000 years ago.
Researchers reported on the genomic profiles of 13,000 to 8,000-year-old hunter-gatherers from the Iberian Peninsula in previous studies.
The studies provided evidence for the survival and continuation of a much older Palaeolithic lineage. The Palaeolithic Period spanned roughly 2.5 million years ago to 10,000 BC.
The lineage has been replaced in other parts of Europe and is no longer detectable.
The DNA of an organism that has died is only preserved for a certain period of time, and under favourable climatic conditions. Therefore, it is a huge challenge for researchers to extract DNA from ancient remains, especially from hot and dry climates.
The findings of the new study will help researchers directly investigate the role of the southern Iberian Peninsula as a refuge for Ice Age populations and potential population contacts across the Strait of Gibraltar (a narrow strait separating the Iberian Peninsula from Morocco in Africa) during the last Ice Age, when sea levels were much lower than today.
Significance of the discovery of the oldest human genome from southern Spain
The individuals from central and southern Europe who lived before the Last Glacial Maximum have a genetic ancestry different from that of the individuals who recolonised Europe after the Last Glacial Maximum.
Researchers did not have much information about the situation in western Europe before and after the Last Glacial Maximum due to a lack of genomic data from critical time periods.
Thanks to the genomic data of the 23,000-year-old individual from Cueva del Malalmuerzo, researchers finally have more data from the time when massive ice sheets covered large parts of Europe.
In the new study, the researchers have described a direct genetic link between a 35,000-year-old individual from Belgium and the new genome from Malalmuerzo.
In a statement released by Max Planck Institute for Evolutionary Anthropology, Vanessa Villalba-Mouco, the first author on the paper, said that thanks to the high quality of the researchers' data, they were able to detect traces of one of the first genetic lineages that settled Eurasia 45,000 years ago.
Villalba-Mouco also said that the team found similarities with a 35,000-year-old individual from Belgium whose ancestry can now be traced further to the 23,000-year-old individual from southern Iberia.
According to the study, the individual from Cueva del Malalmuerzo gives clues about earlier periods of settlement, and also links to the hunter-gatherers of southern and western Europe who lived long after the last Ice Age.
The Iberian Peninsula served as an important refuge for human populations during the last Ice Age, genetic data from the individual has confirmed.
Other mysteries unravelled by the research
Humans migrated from the Iberian Peninsula towards the north and east after the ice sheets had retreated.
Wolfgang Heak, a senior author on the paper, said it is remarkable to find such a long-lasting genetic legacy on the Iberian Peninsula, especially since this pre-Ice Age ancestry had long since disappeared in other parts of Europe.
Despite a distance of only 13 kilometres across the Mediterranean Sea between the southern Iberian Peninsula and North Africa, the researchers did not find any genetic link between the two regions.
Gerd-Christian Weniger from the University of Cologne, and one of the authors on the paper, said the researchers found no evidence of a genetic contribution from North African lineages in Malalmuerzo.
Weniger also said that conversely, there is no evidence of a genetic contribution from southern Spain in the genomes of the 14,000-year-old individuals from the Taforalt cave in Morocco.
The researchers also studied a number of younger individuals from the Neolithic Period, which spanned from around 7,000 BC to 1,000 BC. This is when the first farmers arrived in Europe from the Near East.
According to the study, one can detect the characteristic genetic ancestry of Anatolian Neolithic groups in individuals from Andalucía. This suggests that the early farmers spread over large distances.
Jose Ramos-Muñoz, one of the co-authors on the paper, said Neolithic people from southern Iberia show a higher proportion of hunter-gatherer lineages, which means that the interaction between the last hunters and the first farmers may have been much closer than in other regions.
The Iberian Peninsula played a special role during the Ice Age, and this still resonates thousands of years later.