Ancient Farmers Had Two Distinct Roots

The world’s first farmers sprung from two distinct population cradles, according to new research in which DNA was extracted and analysed from ancient populations in Iran. The findings have just been published in the journal Science by an international team led by the University of Mainz, which involved scientists from Trinity College Dublin.

Sedentism, farming and agriculture was invented some 10,000 years ago in a region between south-eastern Anatolia, Iran, Iraq, and Syria, traditionally known as the “Fertile Crescent”. Most of the technology and culture associated with farming, including that of domestic sheep, goats, cattle, and pigs originated there. The transition from a hunter-gatherer to farming lifestyle was considered such a radical change in human ecology that it coined the term “Neolithic revolution”.

Some 2,000 years later, the new Neolithic lifestyle appeared in south-eastern Europe, and shortly afterwards spread into central and Mediterranean Europe. It also spread eastwards to Pakistan, northern India and beyond.

To trace back the ancestry of these early farmers, the research team retrieved and analysed DNA from 10,000-year-old skeletons of the earliest farmers from the Zagros Mountains in Iran (the eastern part of the Fertile Crescent). The results show that these people were a genetically distinct group, and only very distantly related to the first farmers of western Anatolia and Europe.

Only recently the team showed that the early farmers of Europe traced their ancestry back to Greece and north-western Anatolia, from where Neolithic settlers spread into Europe, bringing their new way of life.

Daniel Wegmann of the University of Fribourg said: “We just assumed this trail of ancestry would lead back to the centre of the Fertile Crescent. But now it appears that the chain of migration into Europe breaks somewhere in eastern Anatolia.”

The group of prehistoric inhabitants of the Zagros region whose DNA was analysed separated from the ancestors of the Neolithic farmers of Europe more than 50,000 years ago. It is therefore interesting that people, who almost certainly looked different and spoke different languages, adopted the agricultural lifestyle roughly simultaneously in different parts of Anatolia and the Near East.

Rui Martiniano, researcher in the School of Genetics & Microbiology at Trinity, said: “The Iranian and Anatolian Neolithic divide is further supported by the paternal lineages we identified. One ancient farmer from the Zagros Mountains belonged to a rare Y-chromosome haplotype discovered for the first time in prehistoric samples, which is different than the one typically associated with the expansion of the first farmers into Europe.”

Archaeo-zoologist Marjan Mashkour works at the CNRS in Paris and initiated the study with the National Museum of Iran and with senior author, Joachim Burger, of the University of Mainz. Marjan Mashkour said: “The Neolithic way of life originates in the Fertile Crescent; maybe also some Neolithic pioneers started moving from there, but the majority of ancient Iranians did not move West as some would have thought.”

But the first farmers of the eastern Fertile Crescent did move east, as the research team found that the Iranian ancient genomes are related to modern-day south Asians.

While sharing many segments of their genome with Afghani and Pakistani populations, the almost 10,000-year-old genomes from the Iranian Zagros Mountains were most similar to modern-day Zoroastrians from Iran. “This religious group probably mixed less with later waves of people than others in the region and therefore preserved more of that ancient ancestry,” said Farnaz Broushaki, first author of the study.

The research also underlines how ancient genome studies can reveal much about past population sizes.

Lara Cassidy, IRC researcher from Trinity’s School of Genetics & Microbiology, said: “What’s fascinating is that both Anatolian and Iranian early farmers appear to come from historically large populations, possibly due to favourable environmental conditions. In sharp contrast, the contemporaneous hunter-gatherers of Europe and the Caucasus belonged to isolated populations, whose small sizes can be visualised through inbreeding patterns in the genome.”

In summary, it appears that at least two divergent groups became the world´s first farmers: the Zagros people of the Neolithic eastern Fertile Crescent that are ancestral to most modern South-Asians, and the Aegeans that colonized Europe some 8,000 years ago.

“The origin of farming was genetically more complex than we thought and instead of speaking of a single Neolithic centre, we should start adopting the idea of a Federal Neolithic Core Zone,” said Joachim Burger.

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