In a multidisciplinary study published in the Proceedings of the National Academy of Sciences (PNAS), an international team of researchers employed a combination of archaeological, genetic, and stable isotope data to unveil 4000 years of biomolecular prehistory in the Iberian Peninsula.
The research team conducted a detailed analysis of human remains from 13 individuals spanning both the northern and southern regions of Spain. Among the sites examined was El Portalón, situated within the well-known Atapuerca site in Burgos, which itself encapsulates four millennia of Iberian prehistory. Additionally, the study delved into crucial locations like Cueva de los Murciélagos in Andalusia, where the genome of a 7,245-year-old Neolithic farmer was sequenced, establishing it as the oldest sequenced genome in southern Iberia, representing the Neolithic Almagra Pottery Culture — the early agriculturalists of southern Spain.
The backdrop of prehistoric migrations holds significance in shaping the genetic makeup of European populations. After the last glacial maximum approximately 20,000 years ago, Europe witnessed the habitation of hunter-gatherer groups. Two major migrations within the last 10,000 years significantly influenced the lifestyle and gene pool of European populations. Firstly, groups originating from the Middle East and Anatolia introduced farming practices during the Neolithic. Subsequently, less than 5,000 years ago, herder groups from the Pontic-Caspian steppe expanded across the European continent. Given the eastern origins of these movements, the westernmost parts of the continent were the last to be reached by these migrations.
Archaeogenetic studies have indicated that both of these migrations extensively replaced more than half of the gene pool in Central and Northern Europe. However, the influence of these events on Iberian populations, particularly in the southern areas like Andalusia, has remained relatively less explored.
The study challenges existing notions about the genetic composition of early farmers in Iberia. Unlike Central and Northern Europe, Neolithic Iberians exhibit genetic distinctions, suggesting that their ancestry aligns more closely with the initial Neolithic migrants rather than the later contributions from central European counterparts. The researchers emphasize that early farmers in Iberia likely trace the majority of their ancestry to the first Neolithic people who migrated into the peninsula.
The migratory routes of the first farmers into Iberia primarily followed a coastal path through the northern Mediterranean Sea. The study establishes that these Neolithic Iberians show genetic differences compared to migrant farmers in Central and Northern Europe. “This suggests that all early farmers in Iberia trace most of their ancestry to the first Neolithic people that migrated into the peninsula and that later contributions from their central European counterparts were only minor,” says archaeogeneticist Cristina Valdiosera from La Trobe University in Australia, one of the lead authors of the study.
These migrants following the Mediterranean route exhibit a robust genetic connection with modern-day inhabitants of the Mediterranean island of Sardinia. “We can probably consider modern Sardinians relatively direct descendants of the people who spread farming practices across the Mediterranean region around 8,000 years ago,” adds Mattias Jakobsson, population geneticist at Uppsala University, Sweden, and one of the senior authors of the study.
Despite the existence of potential alternative entry points into Iberia, such as North Africa or mainland Europe, the researchers did not find substantial regional differences within Iberia. Torsten Günther, population geneticist at Uppsala University and one of the lead authors of the study, notes, “While geographic differences seem minor, we do see some differences over time due to interaction and genetic exchange between groups.” The first Iberian farmers, as revealed by the study, showed remarkably low levels of genetic diversity, indicating that the initial wave of eastern migration to establish itself on the peninsula was relatively small. Following this period of low diversity, the newly arrived populations grew in size and mixed with the local hunter-gatherers, rapidly increasing genetic diversity during later periods.
Despite the well-established evidence indicating a significant migration of Pontic-Caspian steppe herders during the Late Neolithic/Bronze Age transition, recent findings highlight a strikingly low genetic impact on contemporary southwestern Europeans, specifically the prehistoric Iberians. In contrast to the substantial population turnover observed in central and northern Europe, the genetic influence of these later migrations in Iberia appears to be minor. This underscores the distinctive genetic history of Iberia, where the predominant influence stems from the primary prehistoric migration linked to the introduction of farming practices—the transformative Neolithic Revolution.
Homogenous diet in Iberian farmers
In their exploration, the researchers delved into the dietary patterns of Neolithic farmers spanning nearly 4000 years, revealing a consistent trend. Despite significant biological interactions among culturally diverse groups, the farming culture not only prevailed from the outset but endured over time. Colin Smith, a molecular archaeologist from La Trobe University and one of the senior authors, elucidates, “Curiously, while we observe a considerable genetic infusion of hunter-gatherer ancestry into farmers across the ages, the dietary habits of these early farmers remain unaltered. Their terrestrial diet, characteristic of farming cultures, persists both temporally and geographically throughout the millennia.”
The study serves as a testament to the potency of interdisciplinary research in unraveling the intricacies of European prehistory. Dr. Valdiosera, in conclusion, underscores the significance of these findings, stating, “In essence, these results underscore the distinctions between the populations in the westernmost regions and their counterparts in central Europe, emphasizing the necessity for detailed regional studies to unveil the complete complexity of prehistoric migrations.”
Source: Uppsala University