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NY Times, Oct. 18 2016
How the First Farmers Changed History
By CARL ZIMMER
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
Hundreds of people living there worshiped 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 civilization 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 already 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 civilization that we’re just beginning to
understand,” said Iosif Lazaridis, a postdoctoral researcher at Harvard
Altering False Impressions
The agricultural revolution changed our species and our planet. As bands
of hunter-gatherers began domesticating plants and animals, they quit
the nomadic life, building villages and towns that endured for thousands
A stable food supply enabled their populations to explode, and small
egalitarian groups turned into kingdoms sprawling across hundreds of miles.
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.
But in recent years, Dr. Zeder 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, Dr. Zeder 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 1980s, Dani Nadel, then at Hebrew University, and his colleagues
excavated 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,
Dr. Nadel co-authored a study showing that one of the huts contained
150,000 charred seeds and fruits, including many types, such as almonds,
grapes and olives, that would later become crops. . A stone blade found
at Ohalo II seemed to have been used as a sickle to harvest cereals. A
stone slab was used to grind the seeds. It seems clear the inhabitants
were cultivating wild plants long before farming was thought to have begun.
“We got fixated on the very few things we just happened to see preserved
in the archaeological record, and we got this false impression that this
was an abrupt change,” Dr. Zeder said. “Now we really understand there
was this long period where they’re playing around with resources.”
Many scientists have suggested that humans turned to agriculture under
duress. Perhaps the climate of the Near East grew harsh, or perhaps the
hunter-gatherer population outstripped the supply of wild foods.
But “playing around with resources” is not the sort of thing people do
in times of desperation. Instead, Dr. Zeder argues, agriculture came
about as climatic changes shifted the ranges of some wild species of
plants and animals into the Near East.
Many different groups began experimenting with ways of producing extra
food, which eventually enabled them to start a new way of life: settling
down in more stable social groups.
Enter the geneticists, who have long wondered if they could help solve
the riddle of agriculture’s origins with DNA from human remains
discovered in places like Ain Ghazal.
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.
It isn’t any longer. In two recent studies, geneticists including Dr.
Reich 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.
Dr. Reich and his colleagues — including Ron Pinhasi, an archaeologist
at University College Dublin, and Dr. Lazaridis of Harvard — 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. Dr. Reich’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,” Dr. Lazaridis said. “It was more extreme than anything you
could have imagined was going on.”
Dr. Reich 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.
One Birthplace, or Many?
Archaeologists have welcomed the new results from the geneticists. But
for now, they are interpreting the data in different ways.
Dr. Zeder said that ancient DNA supports a scenario where farmers across
the Fertile Crescent independently invented agriculture, perhaps
repeatedly. But Ofer Bar-Yosef, an archaeologist at Harvard, argues that
full-blown agriculture evolved only once, and then quickly spread from
one group to another.
He points to the increasingly precise dating of archaeological sites in
the Fertile Crescent. Instead of the southern Levant, the oldest sites
with evidence of full-blown agriculture are in northern Syria and
southern Turkey. That’s where Dr. Bar-Yosef thinks agriculture began.
In other parts of the Fertile Crescent, he argues, people were just
toying with farming. Only when they came in contact with the combination
of crops and livestock, and the technology to manage them — what
scientists call the Neolithic package — did they permanently adopt the
“You just map the dates” of the sites at which the evidence for farming
is found, he said, “and you see it’s always later as you get away from
the core area.” The new genetic results simply show that this farming
technology spread through the Fertile Crescent, but that the populations
sharing it did not interbreed.
The new research also shows that even after agriculture was established
across the Fertile Crescent, people remained genetically isolated for
thousands of years.
“If they were talking to each other, they weren’t intermarrying,” said
Garrett Hellenthal, a geneticist at University College London who
collaborated with the Gutenberg University researchers.
But the DNA research also shows that this long period of isolation came
to a sudden and spectacular end.
About 8,000 years ago, the barriers between peoples in the Fertile
Crescent fell away, and genes began to flow across the entire region.
The Near East became one homogeneous mix of people.
Why? Dr. Reich speculated that growing populations of farmers began
linking to one another via trade networks. People moved along those
routes and began to intermarry and have children together. Genes did not
just flow across the Fertile Crescent — they also rippled outward. The
scientists have detected DNA from the first farmers in living people on
“There seem to be expansions out in all directions,” Dr. Lazaridis said.
Early farmers in Turkey moved across the western part of the country,
crossed the Bosporus and traveled into Europe about 8,000 years ago.
They encountered no farmers there. Europe had been home to groups of
hunter-gatherers for more than 30,000 years. The farmers seized much of
their territory and converted it to farmland, without interbreeding with
The hunter-gatherers clung to existence for centuries, and were
eventually absorbed by bigger farming communities. Europeans today can
trace much of their ancestry to both groups.
The early farmers in what is now Iran expanded eastward. Eventually,
their descendants ended up in present-day India, and their DNA makes up
a substantial portion of the genomes of Indians.
And the people of Ain Ghazal? Their population expanded into East
Africa, bringing crops and animals with them. East Africans retain
ancestry from the first farmers of the southern Levant — in Somalia, a
third of people’s DNA comes from there.
Dr. Reich hopes to learn more about the early farmers by obtaining
samples more systematically from across the Fertile Crescent. “It’s not
easy to come by these unique and special specimens,” he said.
But he is pessimistic about filling in some of the most glaring gaps in
the genetic map of the Fertile Crescent. No one has yet recovered DNA
from the people who lived in the oldest known farming settlements. And
it’s unlikely they’ll be trying again anytime soon. To do so, they would
have to venture into the heart of Syria’s civil war.
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