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DNA from ancient skeletons suggests farming was invented multiple times in the Fertile Crescent

Scientists have discovered an ancient population of farmers from the eastern part of the Fertile Crescent, and their existence is a strong sign that agriculture was invented more than once, a new study says.

Bones and teeth from four human skeletons clearly show that these people were eating domesticated crops at least 9,000 years ago. But their DNA reveals that none of them is an ancestor to the Aegeans, who are considered Europe’s first farmers.

In fact, the four individuals found in present-day Iran are from a distinct genetic group that scientists hadn’t even known existed, according to a report published Thursday by the journal Science.

Among people alive today, the four farmers are most closely related to the Zoroastrians of Iran, the study authors wrote. The ancient farmers probably had “brown eyes, relatively dark skin, and black hair,” the researchers added.

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Of the four skeletons, the most well-preserved bones belonged to a man who was found in Wezmeh Cave in western Iran’s Zagros region. Carbon-dating techniques suggest he lived about 9,100 to 9,500 years ago, and an analysis of the collagen in his bones showed he ate quite a lot of cultivated grains and relatively little meat.

The other three skeletons were found at a site in western Iran known as Tepe Abdul Hosein. One of the individuals, a woman, had cavities and missing teeth — signs that her diet included carbohydrates, which were likely raised as crops.

These three skeletons were about 10,000 years old, and their DNA was more degraded than the DNA from the man in Wezmeh Cave. Still, the researchers were able to tell that all four had “very similar genomic signatures.” Together, they referred to this newly discovered group as “Zagros Neolithics.”

After arising between the Tigris and Euphrates rivers some 10,000 to 12,000 years ago, farming spread northwest from Mesopotamia into Anatolia (present-day Turkey)  and then into Europe, southern Asia, the Arabian peninsula and north Africa.

Although the Zagros people clearly knew a thing or two about farming, it appears they didn’t carry that knowledge out of the Fertile Crescent.

The people who lived in Anatolia during the Neolithic period were descendants of an entirely different genetic group, the researchers found, much to their surprise. They estimated that the ancestors of the Anatolians and the Zagros people split from each other between 46,000 and 77,000 years ago, according to the study.

(As an aside, the researchers also noted that the man from Wezmeh Cave had less Neanderthal ancestry than most non-Africans alive today.)

The fact that humanity’s agricultural know-how was able to get to Anatolia without any help from the Zagros Neolithics suggests that farming arose at least twice in ancient Mesopotamia — and possibly many more times than that, the researchers wrote.

"It had been widely assumed that these first farmers were from a single, genetically homogeneous population,” study author Garrett Hellenthal of the Genetics Institute at University College London said in a statement.

Now it appears that “different populations in different parts of the Fertile Crescent were coming up with similar solutions to finding a successful way of life," added co-author Stephen Shennan of UCL’s Institute of Archaeology.

karen.kaplan@latimes.com

Follow me on Twitter @LATkarenkaplan and "like" Los Angeles Times Science & Health on Facebook.

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