Digging Deep: Genetics Gives A Closer Look At The Origins Of The World’s First Farmers

Neolithic (around 10,000 BC), human history saw a watershed: the transition from a nomadic lifestyle involving hunting and gathering to sedentary farming. The area in which this occurred – which stretches all the way from Egypt in the east to Iraq in the west – is known as the Fertile Crescent. This transformation paved the way for humans to colonize every habitable continent on Earth. Slowly, these farming societies were making their way through geographical passages into Europe and Asia, and within another two to three thousand years, nearly all parts of the ancient world would have entered agriculture.

But who were these early farmers? A study published in Cell this week, led by a team of geneticists from Switzerland and Germany, is trying to answer that question by eavesdropping on ancient genomes taken from archaeological remains found in Neolithic Europe and southwest Asia. In particular, the archaeological remains consist of 15 Neolithic individuals (13 farmers, two fishermen) from as far away as Luxembourg in the west and Iran in the east. This was supplemented by ten previously published genomes (six farmers and four hunters).

Previous ancient DNA studies have largely confirmed that early European farmers and European hunter-gatherers were genetically distinct, at least in the early stages of cultivation, and did not intermix until much later. According to these studies, the farmers who inhabited the continent of Europe ~9Kia (a thousand years ago) came from the Aegean basin (mainly Greece and northern Turkey). The DNA of these early farmers in the Aegean bears great resemblance to those of central Anatolia (present-day Turkey) and the southern Levant (present-day Jordan, Israel, and Lebanon).

Previous studies also indicated a genetic similarity between the Epipalaeolithic (a transitional period between the Paleolithic and the Mesolithic, ~20-10 kya) and Neolithic people in Turkey, indicating little gene flow in terms of migrations , and so on.

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Daniel Wegmann, one of the study’s authors spoke about the link between Aegean farmers and farmers from Central Anatolia. Indianexpress.com“The theory of common ancestry appears to be the most likely. But of course other theories may also be plausible. We currently lack high-quality genomes from the southern Levant and cannot test these hypotheses to the degree we would like.”

The work of Marchi et al. (2022) Four main findings. For ease of interpretation, it identifies three population groups: Western, Central, and Eastern. Western metabolism gave rise to a group of European hunter-gatherers who are genetically distinct from modern Europeans. Central metabolism gave rise to the group of Western farmers (from today’s Europe and Turkey) at an early date. Eastern metabolism gave rise to the mass formed by the first farmers of Iran and fishermen in the Caucasus.

The study found that European hunter-gatherers had much lower genetic diversity due to the population bottleneck imposed at the time of the last Ice Age (LGM). The LGM period was between 26-20 kya when the ice sheets were at their maximum extent. After the genetic bottleneck imposed by the Last Glacial Maxima, European hunters split into two ~23 kya subgroups. This is a departure from previous studies that maintained low genetic diversity among European hunter-gatherers as a result of the small population size.

Alternatively, Marchi et al. (2022) found that effective population size (that is, roughly speaking, the number of individuals in a community contributing to the genetic makeup of the next generation through breeding) was actually higher among European hunter-gatherers than in modern early farmers.

The group’s other major discovery was that the western and eastern populations diverged from each other at about 25.6 km, long before the Neolithic period. Metabolic processes diverged in the middle and east about 13.6 kya. However, this date is still much later than what was arrived at earlier. Previous studies He had asserted that the ancestors of European hunters and the ancestors of the first Iranian farmers in 46-77 kya. This, Marchi et al. (2022), due to potentially overlooked population bottlenecks.

Subsequently, populations from northern Turkey and northern Greece diverged ~9.1-9.3 kya, around the same time that the Aegean peninsula was colonized by early Neolithic farmers. Both the Turkish population and the Aegean population show different levels of modern gene flow from western populations, indicating that their interactions with modern fishermen were not completely uniform.

While in the LGM, the eastern and western metabolic processes diverged because they were stuck in pockets not covered by ice sheets, they were able to spread out of these shelters after these ice sheets receded. The period of ~14-12 kya is known as “interstadial”, when temperatures were relatively warmer compared to earlier and later periods. At about 14.2 kya, central hunter-gatherer populations were in contact with the ancestral populations of both hunter-gatherers in the Caucasus and early farmers in Western Europe. Based on the information we have on the glacial extent, the study argues that these “additives” most likely occurred in southeastern Turkey and the northern Levant.

However, it is difficult to determine when and where exactly the early populations differentiated into central Turkey and the Aegean because the ancestors of the first Western farmers not only expanded in the west, but there were also multiple “mixed events” during the interval between regions. They may have been part of the same “expansion wave” of the early farmers in the Aegean Peninsula and central Turkey They share similar genetic signatures. It may also be that the Turkish and Aegean populations had already mixed before moving on to agriculture, or that the hunter-gatherer populations of the Fertile Crescent moved into the area.

The study generally challenges the current idea that all early farmers in Europe owe their cultural and biological origins to the early farmers of the Fertile Crescent. The picture, in fact, is much more complicated, with the early Western farmers experiencing multiple “mixing” events with European hunter-gatherers and the agricultural population of Southwest Asia. in A press release was issued From the University of Bern, Laurent Exover, one of the corresponding authors, explained that “spatial and temporal gaps remain, and this does not mean the end of studies on human evolution in this field.”

The author is a Research Fellow at the Indian Institute of Science (IISc), Bengaluru, and an independent science panellist. tweeted at Tweet embed