Where did the first farmers live?
Carl Zimmer November 8, 2016 The New York Times
Beneath a rocky slope in central Jordan lie the remains of a 10,000-year-old village called Ain Ghazal, whose inhabitants lived in stone houses with timber roof beams, the walls and floors gleaming with white plaster. Hundreds of people living there worshipped in circular shrines and made haunting, wide-eyed sculptures that stood three feet high. They buried their cherished dead under the floors of their houses, decapitating the bodies in order to decorate the skulls.
But as fascinating as this culture was, something else about Ain Ghazal intrigues archaeologists more: it was one of the first farming villages to have emerged after the dawn of agriculture. Around the settlement, Ain Ghazal farmers raised barley, wheat, chickpeas and lentils. Other villagers would leave for months at a time to herd sheep and goats in the surrounding hills. Sites like Ain Ghazal provide a glimpse of one of the most important transitions in human history: the moment that people domesticated plants and animals, settled down, and began to produce the kind of society in which most of us live today. But for all that sites like Ain Ghazal have taught archaeologists, they are still grappling with enormous questions. Who exactly were the first farmers? How did agriculture, a cornerstone of civilisation itself, spread to other parts of the world?
Some answers are now emerging from a surprising source: DNA extracted from skeletons at Ain Ghazal and other early settlements in the Near East. These findings have challenged long-held ideas about how agriculture and domestication arose. What’s more, the new data are showing that early farmers would leave a tremendous mark. People from Ireland to India trace some of their ancestry to people who began growing barley and wheat in the Near East thousands of years ago. “It’s a part of the story of civilisation that we’re just beginning to understand,” said Iosif Lazaridis, a postdoctoral researcher at Harvard Medical School.
Altering false impressions
Agriculture originated in a few small hubs around the world, but probably first in the Fertile Crescent, a region of the Near East including parts of modern-day Iraq, Syria, Lebanon, Israel and Jordan. The evidence for full-blown agriculture there — crops, livestock, tools for food preparation, and villages — dates back about 11,000 years. In the 1990s, archaeologists largely concluded that farming in the Fertile Crescent began in Jordan and Israel, a region known as the southern Levant.
“The model was that everything started there, and then everything spread out from there, including maybe the people,” said Melinda A Zeder, a senior research scientist at the Smithsonian National Museum of Natural History, Washington D C, USA. But in recent years, Melinda and other archaeologists have overturned that consensus. Their research suggests that people were inventing farming at several sites in the Fertile Crescent at roughly the same time. In the Zagros Mountains of Iran, for example, Melinda and her colleagues have found evidence of the gradual domestication of wild goats over many centuries around 10,000 years ago.
People may have been cultivating plants earlier than believed, too. In the late 1980s, Ofer Bar-Yosef of Harvard and his colleagues began excavating a 23,000-year-old site on the shores of the Sea of Galilee known as Ohalo II. It consisted of half a dozen brush huts. Last year, Ofer and his colleagues reported that one of the huts contained 150,000 charred seeds and fruits.
DNA breakthroughs
Ancient genetic material can survive in skeletons for thousands of years, sometimes even hundreds of thousands of years. Scientists have been able to reconstruct entire genomes of ancient humans and extinct relatives like Neanderthals. But a number of attempts to get DNA out of skeletons in the Near East failed. It looked as if the conditions in the region were too harsh for ancient DNA to survive.
“Genetically, the Near East was terra incognita,” said David Reich, a geneticist at Harvard Medical School, Boston, USA. It isn’t any longer. In two recent studies, geneticists including David used new methods to fish out enough DNA from the bones of the first farmers to figure out their relationship to other people. A team of researchers based at Johannes Gutenberg University in Mainz, Germany, reconstructed the genomes of four early farmers from the Zagros Mountains whose bones date back as much as 10,000 years. David and his colleagues recovered genetic material from 44 sets of remains around the Near East. Their haul included DNA from early farmers in Iran, as well as from bones from another site in the Southern Levant like Ain Ghazal.
David’s group discovered even older genetic material from hunter-gatherers in the region, from as far back as 14,000 years ago. The new results all point to the same overall conclusion: the first farmers in each region were the descendants of the earlier hunter-gatherers. What’s more, each population had its own distinct ancestry, going back tens of thousands of years. They were as different from one another genetically as the Europeans and Chinese.
And these groups remained distinct through the agricultural revolution as they changed from hunter-gatherers to full-blown farmers. “It was quite surprising to see how different these groups were from each other,” Iosif said. David and others argue that the findings show that people around the fertile crescent became farmers independently. “It’s not like you had one Near Eastern population that developed farming that expands and overruns all the others,” he said.
But as fascinating as this culture was, something else about Ain Ghazal intrigues archaeologists more: it was one of the first farming villages to have emerged after the dawn of agriculture. Around the settlement, Ain Ghazal farmers raised barley, wheat, chickpeas and lentils. Other villagers would leave for months at a time to herd sheep and goats in the surrounding hills. Sites like Ain Ghazal provide a glimpse of one of the most important transitions in human history: the moment that people domesticated plants and animals, settled down, and began to produce the kind of society in which most of us live today. But for all that sites like Ain Ghazal have taught archaeologists, they are still grappling with enormous questions. Who exactly were the first farmers? How did agriculture, a cornerstone of civilisation itself, spread to other parts of the world?
Some answers are now emerging from a surprising source: DNA extracted from skeletons at Ain Ghazal and other early settlements in the Near East. These findings have challenged long-held ideas about how agriculture and domestication arose. What’s more, the new data are showing that early farmers would leave a tremendous mark. People from Ireland to India trace some of their ancestry to people who began growing barley and wheat in the Near East thousands of years ago. “It’s a part of the story of civilisation that we’re just beginning to understand,” said Iosif Lazaridis, a postdoctoral researcher at Harvard Medical School.
Altering false impressions
Agriculture originated in a few small hubs around the world, but probably first in the Fertile Crescent, a region of the Near East including parts of modern-day Iraq, Syria, Lebanon, Israel and Jordan. The evidence for full-blown agriculture there — crops, livestock, tools for food preparation, and villages — dates back about 11,000 years. In the 1990s, archaeologists largely concluded that farming in the Fertile Crescent began in Jordan and Israel, a region known as the southern Levant.
“The model was that everything started there, and then everything spread out from there, including maybe the people,” said Melinda A Zeder, a senior research scientist at the Smithsonian National Museum of Natural History, Washington D C, USA. But in recent years, Melinda and other archaeologists have overturned that consensus. Their research suggests that people were inventing farming at several sites in the Fertile Crescent at roughly the same time. In the Zagros Mountains of Iran, for example, Melinda and her colleagues have found evidence of the gradual domestication of wild goats over many centuries around 10,000 years ago.
People may have been cultivating plants earlier than believed, too. In the late 1980s, Ofer Bar-Yosef of Harvard and his colleagues began excavating a 23,000-year-old site on the shores of the Sea of Galilee known as Ohalo II. It consisted of half a dozen brush huts. Last year, Ofer and his colleagues reported that one of the huts contained 150,000 charred seeds and fruits.
DNA breakthroughs
Ancient genetic material can survive in skeletons for thousands of years, sometimes even hundreds of thousands of years. Scientists have been able to reconstruct entire genomes of ancient humans and extinct relatives like Neanderthals. But a number of attempts to get DNA out of skeletons in the Near East failed. It looked as if the conditions in the region were too harsh for ancient DNA to survive.
“Genetically, the Near East was terra incognita,” said David Reich, a geneticist at Harvard Medical School, Boston, USA. It isn’t any longer. In two recent studies, geneticists including David used new methods to fish out enough DNA from the bones of the first farmers to figure out their relationship to other people. A team of researchers based at Johannes Gutenberg University in Mainz, Germany, reconstructed the genomes of four early farmers from the Zagros Mountains whose bones date back as much as 10,000 years. David and his colleagues recovered genetic material from 44 sets of remains around the Near East. Their haul included DNA from early farmers in Iran, as well as from bones from another site in the Southern Levant like Ain Ghazal.
David’s group discovered even older genetic material from hunter-gatherers in the region, from as far back as 14,000 years ago. The new results all point to the same overall conclusion: the first farmers in each region were the descendants of the earlier hunter-gatherers. What’s more, each population had its own distinct ancestry, going back tens of thousands of years. They were as different from one another genetically as the Europeans and Chinese.
And these groups remained distinct through the agricultural revolution as they changed from hunter-gatherers to full-blown farmers. “It was quite surprising to see how different these groups were from each other,” Iosif said. David and others argue that the findings show that people around the fertile crescent became farmers independently. “It’s not like you had one Near Eastern population that developed farming that expands and overruns all the others,” he said.
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