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article imageHuman migration — a study of our first road trip out of Africa

By Karen Graham     Sep 22, 2016 in Science
Three studies published in the journal Nature on Wednesday tackle the question of when did humans begin the great migration that led them out of Africa to populate the world.
Homo sapiens evolved in Africa about 200,000 years ago and went on to become great walkers. With our bigger brains came curiosity about the world. People living outside of Africa today can trace their descent to a group of those early humans who took a road trip that led to them populating the globe.
While most scientific knowledge today suggests that the first mass migration out of Africa began as a single wave about 60,000 years ago, there has been some question about a possible earlier migration, based on both archaeological and genomic studies.
Migration out of Africa
Migration out of Africa
Spreading homo Sapiens.jpg which is in the public domain
On Wednesday, a trio of genetic analysis studies was published in the online journal Nature suggests that with one tiny exception, all people living today are descendants of that same wave of humans that left the African continent some 60,000 years ago.
That does not mean there weren't other smaller migrations before or after the one mass migration event. “I think all three studies are basically saying the same thing,” said Joshua M. Akey of the University of Washington, in a commentary accompanying the new work. “We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one.”
The one tiny exception
But take note of the phrase, "one tiny exception." This is where it gets interesting and somewhat complex, especially for genomic studies, according to Discover. So the clues that indicate earlier migrations are staring us in the face.
The skulls found in caves on Israel s Mt. Carmel have been tentatively dated at about 80 000-120 000...
The skulls found in caves on Israel's Mt. Carmel have been tentatively dated at about 80,000-120,000 years old using electron paramagnetic resonance and thermoluminescence dating techniques.
Wapondaponda/Wikimedia Commons
Human remains found in caves on Israel’s Mount Carmel were found to be about 115,000 years old. And in China, scientists have found human teeth, said to be at least 80,000 years old and perhaps as old as 120,000 years.
These and other finds lend credence to the idea that there were earlier tries at migration out of Africa, but the big question there is "What became of the people?" It has now been surmised that humans from these earlier migrations died out, either on their own or with the help of later migrations.
Natives of Papua New Guinea
The one tiny exception is the natives of Papua New Guinea. Over 500 genomes from 270 indigenous groups from around the world were studied, including a number of groups that had never been studied to any great extent.
Natives of Papua New Guinea possess 2.0 percent of a genome that shows an independent expansion out ...
Natives of Papua New Guinea possess 2.0 percent of a genome that shows an independent expansion out of Africa about 120,000 years ago.
eGuide Travel
But in natives from Papua New Guinea, the researchers found that 2.0 percent of their genomes show DNA evidence of an earlier migration of home sapiens out of Africa. This particular evidence was not found in any of the other population groups studied, says the BBC.
Dr. Luca Pagani and Dr. Mait Metspalu, director of the Estonian Biocentre in Tartu, told BBC News, "The first instance when we thought we were seeing something was when we used a technique called MSMC, which allows you to look at split times of populations."
They found that with all Eurasians, there was a very homogenous mix of genomes in their split. "This suggests most Eurasians diverged from Africans in a single event... about 75,000 years ago, while the [Papua New Guinea] split was more ancient - about 90,000 years ago. So we thought there must be something going on."
After further breaking down the gene splits, they concluded that the Papua New Guinea genome "originated as an independent expansion out of Africa about 120,000 years ago," Dr. Pagani told BBC News. "We believe this makes up at least 2.0 percent of the genome of modern [Papua New Guineans]."
Sunrise in Africa. Regardless of where we live in the world today  we owe it to those early humans t...
Sunrise in Africa. Regardless of where we live in the world today, we owe it to those early humans that took the raod trip of a lifetime.
Jon Sullivan
Commenting on the conclusions reached in all three studies, Dr. Pagani said, "All three papers all reach the same conclusions. That in Eurasians and also [Papua New Guineans] - the majority of their genomes come from the same major migration."
All three of the studies described in this article can be found in the September 22, 2016, online issue of Nature, the international weekly journal of science.
More about human migration, Homo sapiens, Human genome, Dna evidence, three separate studies
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