Analysis of DNA from some of the world's first farmers shows that they had surprisingly diverse origins. The results shed some light on a debate on whether farming spread out from a single source in the region, or whether multiple farmer groups spread their technology across Eurasia.
The current findings of an international team appear in Science journal.
The switch from mobile hunting and gathering to the sedentary lifestyle of farming first occurred about 10,000 years ago in south-western Asia. After the last Ice Age, this new way of life spread rapidly across Eurasia, in one of the most important behavioral transitions in human history.
In the new study, researchers show that the DNA of early farmers who lived in Zagros mountain in Iran was very different from that of the people who spread farming west through Turkey into Europe.
Despite the fact that both of these groups inhabited the Fertile Crescent, they appear to have separated genetically between 46,000 and 77,000 years ago.
The DNA of the Zagros mountains famers most closely resembles that of living people from Afghanistan, Pakistan and Iran - and Iranian Zoroastrians in particular. Zoroastrians are the people who practice an ancient pre-Islamic religion of present-day Iran.
The present-day population whose genomes most closely resemble the western farmers is found not in the Middle East, but on the Italian island of Sardinia.
This reveals the scale of genetic change in the Fertile Crescent since the Neolithic. After the invention of agriculture, divergent groups of Middle Eastern farmers mixed thoroughly, and the region received genetic inputs from populations residing in surrounding areas.
As a consequence, human diversity was lost due to the differential expansion of a few populations.
What the early farmer populations do share is ancestry from an enigmatic group of humans known as Basal Eurasians. After humans left Africa, this population split away other non-Africans and somehow avoided interbreeding with Neanderthals. But it is still unclear where exactly these ancient people resided until they mixed with the ancestors of the farmers.
Basal Eurasians are often referred to as "ghost populations," as they are only inferred from genetic data through their ancestral contribution to other human groups like the first Middle Eastern farmers - and by extension modern human groups from India to western Europe.
Source: BBC
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