The adoption of farming, possibly the biggest technological development of all time, involved several independent populations within the area known as the Fertile Crescent, new evidence reveals. We still don't know if some groups copied others, but it appears a single tribe did not discover the benefits of agriculture and use this to take over the entire region.
Well-preserved DNA has been retrieved from a skeleton found in Wezmeh Cave, western Iran, and dated as more than 9,000 years old. DNA from a another three skeletons approximately 1,200 years older from nearby Tepe Abdul Hosein were in poorer condition, but still sufficiently intact to provide some information about the inhabitants of the era. The hot climate of the region has destroyed most DNA from the time, but the researchers took advantage of the fact that the ear bones are so rich in DNA that even hostile conditions will not always destroy it all.
Now, a large team of scientists have come together to analyze these samples, publishing their findings in Science.
The carbon and nitrogen isotopes found in all four skeletons are consistent with people who consumed a diet of cereals, rather than animal protein, suggesting that these were farmers rather than hunter-gatherers. If so, they would be among the earliest evidence we have of the transition to settled lifestyles.
“All four Neolithic Iranian individuals are genetically more similar to each other than to any other [known] prehistoric genome except a Chalocolithic genome from north-west Anatolia [modern-day Turkey],” the authors report. This is despite the huge time gap between them.
The paper states: “These people are estimated to have separated from Early Neolithic farmers in Anatolia some 46-77,000 years ago.” The closest modern relatives the authors could find are Iranian Zoroastrians, whose religious identity has kept them largely distinct from the populations in which they live. There are also what the authors call “affinities” with populations as far afield as Pakistan and Afghanistan.
Early European farmers were descended from a distinct group of early farmers within the Fertile Crescent, an area that curves from modern-day Kuwait, through Iraq and surrounding nations, and around to Israel and Jordan. This work shows that those ancestors were not the only people discovering farming at the time.
In an article in the same edition of Science, co-author Dr Garrett Hellenthal of the University College London is quoted as saying: “These early farmers who lived pretty close to each other were completely different.”
The paper leaves unanswered some very intriguing questions. For one, did the Tepe Abdul Hosein peoples invent the idea of cultivating crops independently from other early farmers, or did one group copy from the other while avoiding interbreeding? The authors describe the absence of a genetic legacy for these people among the modern population of Europe and Asia Minor as “surprising”. However, exploring why they left such a small genetic heritage could prove a challenge.