A study published Friday in the journal Science Advances found that only 7% of our genome is uniquely shared with other humans and not shared by other ancestors.
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“That’s a very small percentage,” said Nathan Schaefer, a biologist at the University of California, Berkeley and co-author of the new study. “Because of this kind of discovery, scientists are moving away from the idea that we humans are much more different than the Neanderthals.” The study revealed DNA from the nearly extinct Neanderthals and Denisovans about 40,000 or 50,000 years ago, as well as 279 modern humans from around the world.
Scientists already know that modern humans share some DNA with Neanderthals, but different people share different parts of the genome. One goal of the new study was to identify the exclusive genes of modern humans.
This is a difficult statistical problem, and researchers “created a valuable tool that takes into account missing data in ancient genomes,” says John Wixon, a researcher at the University of Widkinson, University of Medicine.
The researchers also found that a much smaller fraction of our genome – only 1.5% – are both unique to our species and shared among all humans currently living. These sleeves of DNA may contain the most significant clues as to what makes modern humans truly different.
“We can say that areas of the genome are extremely rich in genes that have to do with nerve development and brain function,” said Richard Green, a biology scientist at the University of California, Santa Cruz, who co-authored the study.
In 2010, Green helped create the first draft sequence of a Neanderthal genome. Four years later, geneticist Joshua Aki co-authored a study to show that modern humans carry some remnants of Neanderthal DNA. Since then, scientists have been refining techniques for extracting and analyzing genetic material from fossils.
“Better tools allow us to ask increasingly more detailed questions about human history and evolution,” said Aki, who is now at Princeton and was not involved in the new research. He praised the new research methodology.
But Alan Templeton, a demographer at the University of Washington in St. Louis, questioned the authors’ idea that mutations in the human genome were distributed randomly without enclosing certain hotspots in the genome.
“The findings underscore that we are actually a very small species,” Aki said, “so long ago we shared the planet with other human races.”