The appearance of agriculture, some 12,000 years ago, radically changed the course of our history, but it was still unknown who the first farmers on the planet were. Now a study published in Cell It suggests that the earliest humans to adopt an agricultural lifestyle came from a mix of hunter-gatherer populations in Europe and the Middle East.
This has been clarified by an international team of researchers, led by geneticists from the University of Bern, the University of Freiburg and the Johannes Gutenberg University of Mainz, in a work that uses new genetic evidence to shed light on the origin of the first populations of farmers. Experts conclude that the idea of linking the appearance of agriculture to a single human group in a single region would no longer be viable.
To rewrite the history of the populations that began to cultivate plants, the researchers adopted an approach based on two techniques: on the one hand, obtaining high-quality ancient genomes from prehistoric finds; and, on the other, demographic modelling. The method, which the authors have called ‘demognomic modelling’, makes it possible to build demographic models from ancient DNA.
The approach involves sequencing the genome of ancient humans multiple times, a “deep sequencing” process that generates high-quality genetic data. “This provides much more detail about the demographic history of these populations, from their divergence and expansion to the times when they came into contact,” explains Laurent Excoffier, an expert in population genetics at the University of Bern and co-author of the study. Previous work, based on incomplete genomes, could not reach such a degree of detail.
Previous genomic analyzes suggested a complex origin for early farmers in the Middle East. They assumed that, about 25,000 years ago, a large initial population split into two groups. One of them would have migrated to Europe and would have suffered a drastic reduction in size and genetic impoverishment due to the cooling of global temperatures.
Meanwhile, the other group would have remained in the Middle East and from it would have emerged the population responsible for the most important transformation in our history: the transition from the “wild” way of life of hunter-gatherers to the “domesticated” world of farmers.
The recent findings offer a new interpretation of the dynamics of these populations. “We found that the first farmers in Anatolia and Europe arose from a mixed population of hunter-gatherers from Europe and the Middle East,” says Nina Marchi, a geneticist at the University of Bern and co-author of the study. Deep genome sequencing of fifteen farmers and hunter-gatherers from Europe and Southwest Asia, who lived between 7,000 and 9,000 years ago, has shown that early Neolithic populations were much larger than previously thought. And that would imply that they were more connected, according to the authors.
This old demographic scenario lays the foundations for a new theory about the appearance and expansion of agriculture. This hypothesis holds that, during the warmest phases of the last glacial period (the Würm glaciation, or Ice Age, between 100,000 and 11,000 years ago), populations that had been isolated dispersed and came into contact. Some 14,000 years ago there would have been an encounter between a Western group and an Eastern one that already had great genetic diversity. From that contact a population would have arisen in the Fertile Crescent, the strip of land located between the Tigris and Euphrates rivers and the mouth of the Nile, which would have given rise to agriculture. According to the authors, this is the genetic origin of the architects of the first agricultural revolution.
The story of the first farmers then continued west, where they moved in search of new land to cultivate. About 9,000 years ago, some groups living in the Middle East undertook long journeys (both by sea, following the Mediterranean route, and by land, going up the Danube) and thus began a period of genetic differentiation between European and Eastern populations. Medium. Much of Europe’s current population is descended from groups that arrived on the continent about 7,000 years ago.
The study thus rewrites the evolutionary history of human populations in Europe and the Middle East, clarifying the origin of the first agricultural communities in the world. The results also highlight the importance of deep genome sequencing of ancient DNA to reconstruct human evolution “with high resolution.” The authors envision applying the method to later stages of the Neolithic and Bronze Age.
Article translated and adapted by Research and Science with permission from Le Scienze.
Reference: “The genomic origins of the world’s first farmers». Nina Marchi et al. in Cell, vol. 185, pp. 1842-1859.E18, May 26, 2022.