Genetic origins of the world’s first farmers clarified
New study published in the journal Cell
13 May 2022
The genetic origins of the first agriculturalists in the Neolithic period long seemed to lie in the Near East. A new study published in Cell shows that the first farmers actually represented a mixture of Ice Age hunter-gatherer groups, spread from the Near East all the way to south-eastern Europe. Researchers from Johannes Gutenberg University Mainz as well as from the University of Bern and the University of Fribourg were involved in the study. The method they developed could help reveal other human evolution patterns with unmatched resolution.
The first signs of agriculture and a sedentary lifestyle are found in the so-called Fertile Crescent, a region in the Near East where people began to settle down and domesticate animals and plants about 11,000 years ago. The question of the origin of agriculture and sedentism has occupied researchers for over 100 years: did farming spread from the Near East through cultural diffusion or through migration? Genetic analyses of prehistoric skeletons so far supported the idea that Europe’s first farmers were descended from hunter-gatherer populations in Anatolia. While that may well be the case, this new study shows that the Neolithic genetic origins cannot clearly be attributed to a single region. Unexpected and complex population dynamics occurred at the end of the Ice Age and led to the ancestral genetic makeup of the populations who invented agriculture and a sedentary life-style, i.e., the first Neolithic farmers.
First farmers emerged from a mixing process starting 14,000 years ago
Previous analyses had suggested that the first Neolithic people were genetically different from other human groups from that time. Little was known about their origins. Dr. Nina Marchi, one of the study's first authors from the Institute of Ecology and Evolution at the University of Bern said: "We now find that the first farmers of Anatolia and Europe emerged from a population mixture between hunter-gatherers from Europe and the Near East." According to the authors, the mixing process started around 14,000 years ago, which was followed by a period of extreme genetic differentiation lasting several thousand years.
Novel approach to model population history from prehistoric skeletons
This research was made possible by combining two techniques: the production of high-quality ancient genomes from prehistoric skeletons, coupled with demographic modeling on the resulting data. The research team coined the term "demogenomic modeling" for this purpose. "It is necessary to have genome data of the best possible quality so that the latest statistical genomic methods can reconstruct the subtle demographic processes of the last 30,000 years at high resolution", said Laurent Excoffier, one of the senior authors of the study. He initiated the project together with Professor Joachim Burger of Johannes Gutenberg University Mainz and Daniel Wegmann of the University of Fribourg. Laura Winkelbach, also first author and responsible for the production of the ancient genomes, added: "The field of palaeogenomics is still very young. We have spent years optimizing our lab methods to make the production of such high-resolution palaeogenomes feasible. Only about ten percent of the skeletons contained sufficient DNA for intensive examination." In fact, the JGU-based anthropologists produced about 20,000 times more DNA sequences per skeleton for this study than is usual in the field. The work for this is done in the highly specialized palaeogenetic laboratories of Mainz University, which are among the largest of their kind in the world.
Towards a general model of the evolution of human populations in Southwest Asia and Europe
Professor Joachim Burger of Johannes Gutenberg University Mainz and senior author emphasized the necessity of interdisciplinarity: "It took close to ten years to gather and analyze the skeletons suitable for such a study. This was only possible by collaborating with numerous archaeologists and anthropologists, who helped us to anchor our models historically." The historical contextualization was coordinated by Dr Maxime Brami, who works with Burger at JGU. The young prehistorian was surprised by some of the study's findings: "Europe's first farmers seem to be descended from hunter-gatherer populations that lived all the way from the Near East to the Balkans. This was not foreseeable archaeologically." Professor Joachim Burger added: "With these approaches, we have not only elucidated the origins of the world’s first Neolithic populations, but we have established a general model of the evolution of human populations in Southwest Asia and Europe."
"Of course, spatial and temporal gaps remain, and this does not imply the end of studies on the evolution of humans in this area," concluded Laurent Excoffier. Thus, the team's research plan is already set. They want to supplement their demographic model with genomes from the later phases of the Neolithic and Bronze Ages to provide an increasingly detailed picture of human evolution.