The invention of farming some 10,000 years ago set the stage for the rise of civilisations in Asia. Yet archaeologists disagree about how it happened.
Some say it arose in a single spot near the Mediterranean, and spread from there. Others argue it had multiple independent origins, a view that is getting new credence, thanks to findings from an early farming site in Iran.
Whether farming arose once or a hundred times, it happened first in the Fertile Crescent, a broad region stretching from the Mediterranean Sea to Iran.
Most research over the past decades has focused on the western stretches of the Fertile Crescent - including modern-day Israel, Palestine, Syria, Jordan and Turkey - in large part because those were the easiest areas to work in, both logistically and politically.
Recent excavations in those areas have suggested that hunter-gatherers first began to gather and plant seeds from wild cereals and legumes, such as wheat, barley, and lentils, as early as 13,000 years ago.
Over a few thousand years of such cultivation, the wild forms of these plants mutated into new, domesticated species that were easier to manage and harvest, making farming more productive and efficient.
Until recently, the oldest known farming villages had been found at sites in Palestine, Syria, and eastern Turkey, where archaeologists radiocarbon dated the earliest domesticated plant species to about 10,500 years ago.
Only a few sites were known as far east as Iran, and most of them had been excavated in the 1960s and 1970s, before that country's 1979 Islamic Revolution made it nearly impossible for Western archaeologists to work there - and also before the advent of modern archaeobotanical techniques that make it much easier for researchers to recover tell-tale plant remains.
About five years ago, archaeologist Nicholas Conard and archaeobotanist Simone Riehl of the University of Tübingen in Germany hooked up with researchers at the Iranian Center for Archaeological Research (ICAR) in Tehran, and particularly Mohsen Zeidi, an experienced ICAR excavator, to begin work at the early farming village of Chogha Golan, in the foothills of the Zagros Mountains in western Iran.
Iranian archaeologists had discovered the village about 15 years earlier, but never fully excavated it.
While digging in 2009 and 2010, the team uncovered extensive evidence for the processing of plants in the village, including mortars, pestles, and grinding stones.
The dig also yielded a huge quantity - more than 21,000 individual pieces - of charred plant remains, which Riehl analyzed for a report online in Science.
Radiocarbon dating of the archaeological deposits, some 8m in depth, showed that Chogha Golan had been occupied continuously between about 12,000 and 9700 years ago or even later . That allowed Riehl and her colleagues to trace the use of plants over that entire period of time.
They found that the people of Chogha Golan apparently began cultivating wild barley, wheat, and lentils more than 11,500 years ago, and that domesticated forms of wheat appeared about 9800 years ago, nearly as early as at sites to the west.
The team concluded that the advent of farming at Chogha Golan, and in the eastern Fertile Crescent, was an independent event that paralleled developments much farther west.
This suggests, researchers say, that farming was more or less inevitable once the Ice Age had ended and climatic and environmental conditions were right for it, rather than being a fluke that arose in just one location.
"These results do support the idea of multiple origins of agriculture," says Roger Matthews, an archaeologist at the University of Reading in the United Kingdom.
He adds that the findings are consistent with recent DNA studies that also suggest multiple origins for both domesticated plants and animals.
They also echo work that he, along with other British and Iranian archaeologists, has carried out at another Iranian site called Sheikh-e Abad, where it appears that wild goats were herded and penned, "a transitional stage between wild and domesticated that matches well with the transitional stages in plant use" found at Chogha Golan.
George Willcox, an archaeobotanist affiliated with the University of Lyon in France, agrees that the geographical distance of the Zagros Mountains from the western Fertile Crescent could suggest an independent origin for crop cultivation.
But he cautions that "it is too early to argue one way or the other" whether the actual domestication of cereals, as opposed to cultivation of wild forms, was an independent event.
It is still possible, Willcox says, that the domesticated wheat found at Chogha Golan, which at 9800 years was several hundred years younger than the earliest known domesticated species, was introduced from further west.
- SCIENCE NOW
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