Imagine Europeans struggling to cope with waves of migrants while simultaneously grappling with dangerous climate change.
The picture that arises describes Europe today. But it also applies to the continent tens of thousands of years ago.
Analyzing the biggest sampling ever of genetic material from prehistoric humans, dating as far back as 45,000 years — when modern humans first arrived in Europe — an international team of archeologists, biologists, and scientists from other disciplines traced the family tree of Europeans back to their first ancestors.
The result was a bevy of discoveries that show how the first Europeans moved around during the Ice Age and mixed with newcomers who arrived throughout the millennia. Experts said the findings published recently in the journal Nature contain valuable lessons to teach the continent's current occupants.
"We're seeing how our ancestors adapted," said Hélène Rougier, an anthropologist at California State University, Northridge and one of the study authors. "This has resonance for today."
'Everybody is a giant mongrel.'
Rougier and other experts were especially quick to note that the findings were a counterpoint to the xenophobic backlash against the desperate Middle Eastern and North African asylum seekers who have been traveling thousands of miles to reach Germany, Greece, Italy, and other countries.
"Our history is made of migrations. This is part of our ancestry," Rougier said. "So what is happening now are things that happened in the past, and we made it all right."
Some of the earliest Europeans appear to have resided in what is now Belgium, according to a 35,000-year-old fossil, the researchers found. That's an apt location given that Brussels is the capital of the European Union. But the scientists also found that the first Europeans had brown eyes and dark skin. Near Eastern farmers first introduced blue eyes and pale skin to the continent.
"What this is showing is a very important social message," said Ian Tattersall, curator emeritus of the Division of Anthropology at the American Museum of Natural History, who did not work on the study. "Everybody is a giant mongrel."
Those Near Easterners came to Europe around 14,000 years ago, when the weather became warmer. People are now similarly experiencing pressures to change their way of life due to rising sea levels, droughts, and catastrophic storms, said Rougier.
"We're looking at a period during which the climate changed quote a lot," she said. "There were some times when it was a really harsh climate. Some populations decreased in size, maybe migrated to somewhere it was milder, and then they expanded again."
Syria, for example, suffered an extreme drought in the years preceding the 2011 uprising that led to the country's civil war. That drought has been described as exerting a catalytic effect on crop failures, mass migrations to cities, and the ensuing social discord that precipitated the conflict.
The study relates the stories of different groups named after the archeological sites where their bones were first dug up.
The Aurignacians, who drew famous cave paintings in France, dominated Europe and then disappeared around 30,000 years ago as another group, the Gravettians, migrated into Europe. They hunted wooly mammoths. After a period when scientists aren't sure where the Aurignacians went, their genes reappeared on the Iberian Peninsula 19,000 years ago in another group called the Magdalenians who are known for their carvings using reindeer antlers. The Magdalenians moved north as the glaciers of the Ice Age receded. The Near Easterners arrived after.
The study also found that Neanderthals' genes in the first modern human Europeans declined from 3 to 6 percent 45,000 years ago, when the Neanderthals were still active in Europe, to around 2 percent today. Most of the humans had likely mated with the more primitive Neanderthals before arriving in Europe after a trek that began in the original birthplace of mankind in Africa. Neanderthal DNA was slightly "toxic" to humans, researchers said, and likely led to Neanderthal relatives dying off more frequently, reducing the overall Neanderthal imprint in people today via natural selection.
Because modern humans and Neanderthals are related — but different — species, interbreeding between the two didn't lead to offspring as likely to thrive as the product of two modern humans. Research has shown that the immune systems of modern human mothers might have frequently rejected Neanderthal-produced fetuses because of mismatches between the two species' DNA.
The study only used the remains of 51 people. But that's ten times more than other studies that attempted to draw lessons from prehistoric DNA, said the researchers.
Robert DeSalle, curator of molecular systematics at the American Museum of Natural History who did not work on the study, said 51 might seem like a paltry number and more samples would be certainly have been welcomed. But 51 is enough to draw the definitive conclusions contained in the paper. The researchers were able to extract prehistoric genes from bones that were not yet fossilized by differentiating between bacteria and human DNA, he said.
"This is just spectacular technology, stuff that if you told me this was going to be able to be done 10 or 15 years ago, I would have said 'You're crazy,'" DeSalle said.
He believes that the same urge that drives scientists to learn about prehistoric people may have also provoked early humans to investigate the world around them.
"We're a species that likes to move around a lot and likes to explore," DeSalle said. "That's one of the major things that sets us apart from other things. We're also a species that's very much aware of our ancestry, not only where we're going, but where we come from."
Follow John Dyer on Twitter: @johnjdyerjr
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