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Three years ago the genetic analysis of a little finger bone from Denisova cave in the Altai Mountains in Siberia led to a complete genome sequence of a new line of the human family tree - the Denisovans. Now scientists believe that the Denisovans, who lived about 41,000 years ago, somehow managed to cross one of the world’s most prominent marine barriers in Indonesia and later bred with modern humans on their way to Australia and New Guinea.
Wallace’s Line is a significant sea barrier formed by a powerful marine current along the east coast of Borneo and marks the division between European and Asian mammals to the west from marsupial-dominated Australasia to the east. The fauna on either side of the barrier are so different from one another because the marine straight is very hard to cross.
“On one side you have all your tigers and rhinos and monkeys and on the other you have all your marsupials, giant lizards and Australia," said Professor Alan Cooper of the University of Adelaide in Australia. "This is the probably one of the world's most famous biogeographic lines."
Until now it was thought that ancient humans were unable to cross Wallace’s Line, however research conducted by Professor Cooper and Professor Chris Stringer of the Natural History Museum in the UK suggests that genetic patterns can only be explained if the Denisovans succeeded in crossing the barrier.
The researchers found that Denisovan DNA is virtually absent in current populations on mainland Asia, even though this is where the original fossil was found, but was present in indigenous populations in Australia, New Guinea and surrounding areas.
"In mainland Asia, neither ancient human specimens, nor geographically isolated modern Indigenous populations have Denisovan DNA of any note, indicating that there has never been a genetic signal of Denisovan interbreeding in the area," said Professor Cooper. "The only place where such a genetic signal exists appears to be in areas east of Wallace's Line and that is where we think interbreeding took place -- even though it means that the Denisovans must have somehow made that marine crossing."
The findings have implications for our understanding of the technological ability of Denisovans.
"Knowing that the Denisovans spread beyond this significant sea barrier opens up all sorts of questions about the behaviours and capabilities of this group, and how far they could have spread."
Now that researchers have found what the Denisovans achieved, the next logical question should be how?
Ancient River Discovery Confirms Mediterranean Nearly Dried Up in the Miocene
Sedimentary deposits reveal a Nile-sized river system flowing from what are today Turkey and Syria.
A previously unidentified river deposit (Nahr Menashe, green) covers approximately the same surface area as accumulations filling paleo-Nile fluvial valleys (Abu Madi Formation, yellow), and its interpreted age is roughly consistent with the Abu Madi Formation and other nearby deposits (including the Handere Formation, in blue). Credit: Madof et al., 2019, https://doi.org/10.1130/G45873.1, CC BY-2.0
A giant abandoned river system the size of the Nile was recently discovered under the eastern Mediterranean. The ancient river flowed for only about 100,000 years, but the evidence it left behind is helping scientists understand what happened in the region in the late Miocene during the Messinian Salinity Crisis (MSC), when a diminished Mediterranean Sea was isolated from the Atlantic Ocean.
About 6 million years ago, the Strait of Gibraltar, the narrow, rocky channel between present-day Spain and Morocco that connects the Mediterranean and Atlantic, closed. With no water flowing in from the ocean, the Mediterranean slowly evaporated until tectonic activity reopened the channel more than 600,000 years later. The extent of the inland sea’s evaporation during this period has been contested since the MSC was discovered nearly 50 years ago. The new findings, reported in Geology, shed light on just how little water remained.
“In order for there to be a huge river system there…the Mediterranean [basin] would have had to be exposed a fair amount,” says lead author Andrew Madof, a geologist at the Chevron Energy Technology Company in Houston. “Maybe 75 to 80 percent [of the basin] was dried out, but there was probably a lake that this river system was flowing into.”
Madof and his colleagues used two- and three-dimensional seismic data collected offshore Cyprus, Israel, Lebanon, and Syria to image the subsurface of the eastern Mediterranean and map the river’s remains, which constituted a collection of sedimentary deposits they named Nahr Menashe. They determined that the river flowed out of what are today Turkey and Syria, draining into a lake in the dry Mediterranean basin. Sedimentary deposits in the seismic imagery indicated that the deposits had been left along riverbanks instead of undersea.“People have predicted that [rivers] should have been flowing into this part of the Mediterranean, but nobody had ever seen it before. This is the first major discovery [of a paleoriver] in decades.”
A series of small lobes at the former mouth of the river also shows evidence of backstepping, a process that leaves deposits of former shorelines as a sea’s water level rises. The backstepped lobes found in the new study chronicled the lake’s rising water level at the end of the MSC and matched evidence from other river systems around the Mediterranean, such as the Nile and the former Eosahabi, offshore Libya. Evidence from these systems suggests that at the end of the MSC, contributions from these rivers maintained a lake that covered about a fourth of the Mediterranean’s current extent.
“People have predicted that [rivers] should have been flowing into this part of the Mediterranean, but nobody had ever seen it before,” Madof says. “This is the first major discovery [of a paleoriver] in decades.”
Changes in Climate and Tectonic Shifts
Today, no major river system feeds into the eastern Mediterranean. Shifts of the African, Arabian, and Anatolian plates have resulted in much of the region’s water flowing into the Persian Gulf.
But back in the Miocene and possibly before, the prevailing tectonics in the area dictated that water flowed into the Mediterranean. Madof says it’s possible the newly discovered river system was an ancestral Euphrates River, which today flows from Turkey south through Syria and Iraq to the Persian Gulf.
Climate during the MSC likely also contributed to the formation of the river by causing increased rainfall over Turkey and Syria.
Lisa Murphy Goes is a paleoclimatologist at the University of Miami in Florida who has previously modeled the region’s paleoclimate. Her findings indicate that a reduced Mediterranean would have induced atmospheric circulation changes that could have brought increased precipitation to higher-elevation regions in southern Europe, including Turkey, and an entirely evaporated Mediterranean may have led to a drought from southern Europe to northern Africa. The results of such simulations are dependent on just how much the sea dried up, however, she says.
“The question of whether or not the basin, particularly in the east, dried up has been controversial for quite some time,” Murphy Goes says. “In terms of the atmospheric response to such a cataclysmic event, only when we truly know the specifics of the sea level change, can we be confident that there must have been significant hemispheric-wide impacts.”
Madof’s findings—that up to 80% of the basin dried up and a major river fed into the Mediterranean’s small remainder—support Murphy Goes’s findings of increased precipitation in the region.
Although the new results help refine the sea level extent during the MSC, further research is required to determine the full extent of climatic effects the shrunken sea might have had.
—Mara Johnson-Groh ( [email protected] ), Freelance Science Writer
This article is the first in a series made possible through the generous collaboration of the writers and editors of Earth magazine, formerly published by the American Geosciences Institute.
New book reveals Ice Age mariners from Europe were America’s first inhabitants
Some of the earliest humans to inhabit America came from Europe according to a new book Across Atlantic Ice: The Origin of America’s Clovis Culture. The book puts forward a compelling case for people from northern Spain traveling to America by boat, following the edge of a sea ice shelf that connected Europe and America during the last Ice Age, 14,000 to 25,000 years ago. Across Atlantic Ice is the result of more than a decade’s research by leading archaeologists Bruce Bradley of the University of Exeter in the United Kingdom, and Dennis Stanford of the Smithsonian’s National Museum of Natural History in Washington, D.C. Through archaeological evidence, they turn the long-held theory of the origins of New World populations on its head. For more than 400 years, it has been claimed that people first entered America from Asia, via a land bridge that spanned the Bering Sea. We now know that some people did arrive via this route nearly 15,000 years ago, probably by both land and sea. Eighty years ago, stone tools long believed to have been left by the first New World inhabitants were discovered in New Mexico and named Clovis. These distinctive Clovis stone tools are now dated around 12,000 years ago leading to the recognition that people preceded Clovis into the Americas. No Clovis tools have been found in Alaska or Northeast Asia, but are concentrated in the south eastern United States. Groundbreaking discoveries from the east coast of North America are demonstrating that people who are believed to be Clovis ancestors arrived in this area no later than 18,450 years ago and possibly as early as 23,000 years ago, probably in boats from Europe. These early inhabitants made stone tools that differ in significant ways from the earliest stone tools known in Alaska. It now appears that people entering the New World arrived from more than one direction.
Dennis Stanford with Clovis stone points from the collection of the Smithsonian’s National Museum of Natural History. (Photo by Chip Clark)
In “Across Atlantic Ice,” the authors trace the origins of Clovis culture from the Solutrean people, who occupied northern Spain and France more than 20,000 years ago. They believe that these people went on to populate America’s east coast, eventually spreading at least as far as Venezuela in South America. The link between Clovis and contemporary Native Americans is not yet clear. Bradley and Stanford do not suggest that the people from Europe were the only ancestors of modern Native Americans. They argue that it is evident that early inhabitants also arrived from Asia, into Alaska, populating America’s western coast. Their ongoing research suggests that the early history of the continent is far more intriguing than we formerly believed. Some of the archaeological evidence analyzed in the book was recovered from deep in the ocean. When the first people arrived in America, sea levels were nearly 130 meters lower than today. The shore lines of 20,000 years ago, which hold much of the evidence left by these early people, are now under the ocean. This is also the case in Europe.
Clovis-made stone tools in the hands of Bruce Bradley, co-author of Across Atlantic Ice: The Origin of America’s Clovis Culture. (Photo by Jim Wileman)
“We now have really solid evidence that people came from Europe to the New World around 20,000 years ago,” Bradley says. “Our findings represent a paradigm shift in the way we think about America’s early history. We are challenging a very deep-seated belief in how the New World was populated. The story is more intriguing and more complicated than we ever have imagined.” “There are more alternatives than we think in archaeology and we need to have imagination and an open mind when we examine evidence to avoid being stuck in orthodoxy,” Stanford adds. “This book is the result of more than a decade’s work, but it is just the beginning of our journey.” Across Atlantic Ice is published by University California Press, Berkeley.–Source University of Exeter
Common walnut (Juglans regia L.) is a wind-pollinated, monoecious, long-lived, perennial tree cultivated throughout temperate regions worldwide for its timber and edible nuts . In its Asian native range (from Xinjiang province of Western China to the Caucasus through Central Asia) J. regia survives and grows spontaneously in almost completely isolated stands surrounded by arid continental lowland, mountain slopes and highland steppes . Evidence from the fossil pollen record indicates that J. regia occupied these niches since the Pleistocene glaciations . Subsequently, barriers to gene flow, such as the Hindu Kush, Pamir, Tien Shan and Himalaya Mountains, and the progressive desertification of Central Asia during the Holocene promoted the fragmentation and isolation of natural J. regia populations in Asia .
Despite this natural geographic isolation, J. regia and other long-lived perennial tree fruit species evolved under the influence of human management and exploitation . Consequences of human manipulation vary across species because, in general, plant cultivation and domestication is a spatially and temporary dynamic multi-stage process that results in populations ranging from exploited wild plants to cultivated forms that cannot survive without human intervention [5–7]. Typically, the domestication of perennial species has resulted in fundamental changes in the mode of reproduction (clonal propagation) and inflorescence / fruit characteristics [4, 8]. Juglans regia, however, does not meet this broadly endorsed criteria for domestication [9, 10], as its cultivated forms are not essentially different from wild, autochthonous trees. Cultivated walnuts are likely derived from selection of seedlings from geographically distinct natural populations over the course of many thousands of years [10, 11].
Indeed, J. regia has been closely associated with human activities since the Early Bronze Age in Asia. Fossilized remnants of desiccated walnut seeds have been found in three macro-regions recognized as primary centers of early fruit tree cultivation : the Near-East (Southern Armenia, Areni-1 Cave, 6230–5790 yr. BP) , Central Asia (Kashmir Valley, Pakistan, Kanispur, 5149 yr. BP)  and northeastern China along the Yellow River basin (Hebei Province, Chishan, 7300 yr. BP) . Vahdati  described J. regia as an ancient tree food whose use has been tightly related to the religious beliefs, history and local identity of rural communities. It was constantly traded via networks such as the Persian Royal Road  and the Silk Roads  that connected China and India to Mediterranean regions. These roads linked culturally dissimilar pastoralist and agrarian civilizations from different parts of Eurasia and allowed the exchange of technologies, goods, religions, languages, ideas and agricultural products, resulting in a rich economic and technological synergy that promoted the rise of modernity over several millennia .
The emerging field of plant bio-cultural diversity integrates cultural features that identify distinct human ethnic groups, such as language, life habits, and food, with plant diffusion and traditional seed-management practices / exchanges . For example, there is a close relationship between ethnolinguistic diversity—used as a proxy for human cultural interactions—and the spatial genetic structure of some maize (Zea mays)  and sorghum populations (Sorghum bicolor L.) . A preliminary genetic analysis of J. regia from Yunnan province (China) revealed that village networks and familial relationships contributed to the genetic structure of autochthonous populations of walnut . In light of these findings, we expected that longstanding human contact with walnut, an economically and culturally significant food source that was widespread, highly nutritious, easily harvested, transported and consumed (requiring no special knowledge to grow or cook),–will have affected the spatial genetic structure of J. regia in Asia.
In the present study we evaluate the hypothesis that the current distribution of autochthonous populations of common walnut in Asia is the product of ancient anthropogenic dispersal and human cultural interactions. In particular, we draw on linguistic and anthropological evidence to determine if (i) major ancient trade routes such as Silk Roads acted as “gene corridors”, facilitating human-mediated gene flow among autochthonous common walnut populations in Asia, and (ii) the presence of ethno-linguistic barriers, reflecting cultural differences among human communities, influenced the genetic structure of autochthonous J. regia populations in Asia.
How sea levels changed after the ice ages around Australia is now well known. So if these stories are accepted as authentic and based on observations of coastal flooding, it is clear that they must be of extraordinary antiquity.
The historical record shows when parts of the Australian coast flooded. Nick Reid & Patrick Nunn , Author provided
How do we know that these stories are authentic? We suggest that because they all say essentially the same thing, it is more likely that they are based on observation. All tell of the ocean rising over areas that had previously been dry. None tell stories running the other way – of seas falling to expose land.
The huge distances separating the places from which the stories were collected – as well as their unique, local contexts – makes it unlikely that they derived from a common source that was invented.
For such reasons, we regard the common element in these stories about sea level inundating coastal lowlands, sometimes creating islands, as based on observations of such an event and preserved through oral traditions.
This conclusion in turn raises many interesting questions.
Ancient migration was choice, not chance, study finds
A candidate bamboo craft for the Ryukyu migration built for a re-enactment of that crossing. Credit: © 2020 Yosuke Kaifu
The degree of intentionality behind ancient ocean migrations, such as that to the Ryukyu Islands between Taiwan and mainland Japan, has been widely debated. Researchers used satellite-tracked buoys to simulate ancient wayward drifters and found that the vast majority failed to make the contested crossing. They concluded that Paleolithic people 35,000-30,000 years ago must therefore have made the journey not by chance but by choice.
Human migration over the last 50,000 years is an essential part of human history. One aspect of this story that fascinates many is the ways in which ancient people must have crossed between separate land masses. Professor Yosuke Kaifu from the University Museum at the University of Tokyo and his team explore this subject, in particular a crossing known to have taken place 35,000-30,000 years ago from Taiwan to the Ryukyu Islands, including Okinawa, in southwestern Japan.
"There have been many studies on Paleolithic migrations to Australia and its neighboring landmasses, often discussing whether these journeys were accidental or intentional," said Kaifu. "Our study looks specifically at the migration to the Ryukyu Islands, because it is not just historically significant, but is also very difficult to get there. The destination can be seen from the top of a coastal mountain in Taiwan, but not from the coast. In addition, it is on the opposite side of the Kuroshio, one of the strongest currents in the world. If they crossed this sea deliberately, it must have been a bold act of exploration."
This issue of the intentionality of this journey is less straightforward to solve than you might imagine. To investigate the likelihood of the journey occurring by chance, the effect of the Kuroshio on drifting craft needed measuring. To do this, Kaifu and his team used 138 satellite-tracked buoys to trace the path of a would-be drifter caught on this journey.
"The results were clearer than I would have expected," said Kaifu. "Only four of the buoys came within 20 kilometers of any of the Ryukyu Islands, and all of these were due to adverse weather conditions. If you were an ancient mariner, it's very unlikely you would have set out on any kind of journey with such a storm on the horizon. What this tells us is that the Kuroshio directs drifters away from, rather than towards, the Ryukyu Islands in other words, that region must have been actively navigated."One of the satellite-tracking buoys. Credit: © 2020 Lagrangian Drifter Laboratory/University of California, San Diego
You might wonder how we can be so sure the current itself is the same now as it was over 30,000 years ago. But existing evidence, including geological records, tell researchers that currents in the region have been stable for at least the last 100,000 years. As for the researchers' confidence that Paleolithic voyagers would not dare face stormy conditions that might otherwise explain chance migrations, prior research suggests that these voyagers were groups including families, whose modern-day analogs do not take such risks.
"At the beginning, I had no idea how to demonstrate the intentionality of the sea crossings, but I was lucky enough to meet my co-authors in Taiwan, leading authorities of the Kuroshio, and came across the idea of using the tracking buoys," said Kaifu. "Now, our results suggest the drift hypothesis for Paleolithic migration in this region is almost impossible. I believe we succeeded in making a strong argument that the ancient populations in question were not passengers of chance, but explorers."
How Ancient Humans Reached Remote South Pacific Islands
Some 3,400 years ago, before the Iron Age or the rise of Ancient Greece, people on the Solomon Islands left their white sandy shores for the cerulean seas of the South Pacific. Their adventures brought humanity to the most remote reaches of Oceania, like the tropical islands of Hawaii, Tonga and Fiji.
“The first ones were traveling into the unknown,” said Alvaro Montenegro, a geographer and climatologist from Ohio State University. “They would leave the coast, and it would disappear behind them.”
Archaeological evidence suggests that after setting sail from the Solomon Islands, people crossed more than 2,000 miles of open ocean to colonize islands like Tonga and Samoa. But after 300 years of island hopping, they halted their expansion for 2,000 years more before continuing — a period known as the Long Pause that represents an intriguing puzzle for researchers of the cultures of the South Pacific.
“Why is it that the people stopped for 2,000 years?” said Dr. Montenegro. “Clearly they were interested and capable. Why did they stop after having great success for a great time?”
To answer these questions, Dr. Montenegro and his colleagues ran numerous voyage simulations and concluded that the Long Pause that delayed humans from reaching Hawaii, Tahiti and New Zealand occurred because the early explorers were unable to sail through the strong winds that surround Tonga and Samoa. They reported their results last week in the journal of the Proceedings of the National Academy of Sciences.
“Our paper supports the idea that what people needed was boating technology or navigation technology that would allow them to move efficiently against the wind,” Dr. Montenegro said.
The researchers studied climate data from the area to better understand the environmental conditions the explorers would have faced on their journeys. They also examined data on El Niño and La Niña conditions as well as wind and current directions and intensities.
Their computer simulations showed that the wind was an essential part of the early human expansion to these islands. While they sailed east from the Solomon Islands to Tonga and Samoa, the wind was at their backs, providing a smooth trip forward that let them populate islands like Fiji and Vanuatu. But after reaching this part of the Pacific, Samoa in particular, the environmental conditions changed significantly. At that point, instead of traveling with the wind they needed to travel against it to progress across the long distances.
Once they found a way to conquer the wind, the ancient people ended their 2,000-year hiatus, and over a period of a few hundred years colonized the rest of Oceania, such as the islands of Hawaii, Tahiti and New Zealand.
Evidence of first ever humans to colonise North America found by scientists
Scientists investigating the DNA of a prehistoric human child have found it belongs to the earliest colonisers of the Americas ever discovered.
The findings suggest Alaska was likely populated 25,000 years ago, 10,000 years earlier than the time of arrival suggested by many archaeologists.
“It represents the oldest lineage of Native Americans so far discovered,” said Professor Eske Willerslev, an evolutionary geneticist at the University of Cambridge who co-authored the study documenting the findings.
“It’s the fact that this population is older than all other known Native American groups that makes it very important in addressing how the Americas were first populated,” he said.
The findings were published in the journal Nature.
Scientists uncover ancient human remains
1 /3 Scientists uncover ancient human remains
Scientists uncover ancient human remains
AFP PHOTO/HO/Brett Eloff/COURTESY OF LEE BERGER /UNIVERSITY OF THE WITWATERSRAND
Scientists uncover ancient human remains
Scientists uncover ancient human remains
The scientists have called this new population the Ancient Beringians, and so far they are only known from the single individual they studied.
Known as "Xach'itee'aanenh T'eede Gaay", or sunrise girl-child, by the local indigenous people, the remains of the Ancient Beringian girl provided Professor Willerslev and his colleagues extensive insight into American prehistory.
The child herself lived 11,500 years ago at a site known as Upward Sun River in Alaska.
However, comparison of the number of genetic similarities and differences with those of other ancient and contemporary humans allowed the scientists to roughly time the movement of ancient people from Asia to North America to a much earlier date.
Their analysis suggested Ancient Beringians and the ancestors of other Native Americans all descend from a single founding population that split decisively from East Asians around 25,000 years ago.
"It would be difficult to overstate the importance of this newly revealed people to our understanding of how ancient populations came to inhabit the Americas," said Dr Ben Potter, an anthropologist at the University of Alaska Fairbanks and one of the lead authors of the study.
"This new information will allow us a more accurate picture of Native American prehistory. It is markedly more complex than we thought."
Contrary to the research team’s expectations, the ancient girl’s DNA did not match the genetic profile of other ancient Native American people from the north.
This suggested the Ancient Beringian population split from other Native Americans 20,000 years ago when the latter moved south along the Pacific coast.
Once further down the coast, Native Americans split into two distinct genetic groups, one in the north and one in the south.
The northern group then moved back further north, pushing out the Ancient Beringians.
As for the modern indigenous inhabitants of Alaska, it is unclear exactly what connection they have with these ancient people.
"These findings create opportunities for Alaska native people to gain new knowledge about their own connections to both the northern Native American and Ancient Beringian people," said Dr Potter.
Professor Willerslev said to the best of their knowledge Alaskan Native Americans do not directly descend from the Ancient Beringians, instead deriving their genes from the northern population of Native Americans who returned to the region.
“However, that said few Natives from Alaska have been sequenced so far, and who knows if some of them survived? Time will tell,” he said.
Homo erectus: Early humans were able to speak and crossed sea on boats, expert claims
Early humans may have learned to speak far earlier than previously thought.
Far from being “stupid ape-like creatures”, a language expert has claimed the ability of Homo erectus to cross bodies of water indicates members of this species were able to talk to one another.
Professor Daniel Everett announced his controversial idea at the annual meeting of the American Association for the Advancement of Science.
The origin of language is shrouded in mystery, with many experts arguing it is a unique characteristic of our species – Homo sapiens. This would mean language dates back no further than our own origins around 200,000 years ago.
The earliest evidence of Homo erectus, on the other hand, dates to around 1.9 million years ago, meaning the timing of the first language could be pushed back considerably.
Professor Everett argued a primitive form of conversation would have been necessary for Homo erectus to achieve what they did.
His hypothesis hinges on the species’ apparent ability to sail across bodies of water.
“Oceans were never a barrier to the travels of Erectus,” Professor Everett, a linguist at Bentley University, told the science conference in Austin, Texas.
“They sailed to the island of Crete and various other islands. It was intentional – they needed craft and they needed to take groups of 20 or so at least to get to those places.”
After originating in east Africa, Homo erectus spread across the world. Their remains have been found throughout Europe and Asia.
Some experts have argued a mysterious species likened to "hobbits", Homo floresiensis, which was discovered on the island of Flores in Indonesia, was descended from Homo erectus .
“Erectus needed language when they were sailing to the island of Flores. They couldn’t have simply caught a ride on a floating log because then they would have been washed out to sea when they hit the current,” Professor Everett told the audience.
“They needed to be able to paddle. And if they paddled they needed to be able to say ‘paddle there’ or ‘don’t paddle.’ You need communication with symbols, not just grunts.”
While the idea was welcomed by some, Professor Everett also met criticism from experts in human origins.
“I don’t accept that, for example, Erectus must have had boats to get to Flores,” said Professor Chris Stringer of the Natural History Museum, arguing that tsunamis could have transported these early humans between islands on rafts of vegetation.
Professor Everett did note that while these early humans could have developed language, it would not have been sophisticated as that used by modern humans.
He described these early attempts as “the Model T Ford of language” compared to the “Tesla form” employed by Homo sapiens.
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 practices.
“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 three continents.
“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 them.
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.