Only 7% of our DNA is unique to modern humans, research shows

Only 7% of our DNA is unique to modern humans, research shows

A study published Friday in the journal Science Advances shows that only a small piece of our genome is uniquely shared with other humans, not shared by other extinct groups such as Neanderthals and Denisovans.

WASHINGTON — What makes people unique? Scientists have taken another step toward solving an enduring mystery with a new tool that allows a more accurate comparison between the DNA of modern humans and that of our extinct ancestors.

Only 7% of our genome is uniquely shared with other humans, not shared by other early ancestors, according to a study published Friday in the journal Science Advances.

“That’s a pretty small percentage,” said Nathan Schaefer, a University of California computational biologist and co-author of the new paper. “Findings like these are why scientists are turning away from the idea that we humans are so vastly different from Neanderthals.”

The research is based on DNA extracted from fossil remains of now-extinct Neanderthals and Denisovans dating back to about 40,000 or 50,000 years ago, as well as from 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 research was to identify the genes that are exclusive to modern humans.

It’s a difficult statistical problem, and the researchers “developed a valuable tool that takes into account missing data in the ancient genomes,” said John Hawks, a paleoanthropologist at the University of Wisconsin, Madison, who was not involved in the study.

The researchers also found that an even smaller portion of our genome — just 1.5% — is both unique to our species and shared by all humans alive today. Those bits of DNA may hold the most important clues about what really sets modern humans apart.

“We can see that those regions of the genome are highly enriched for genes related to neural development and brain function,” said computer biologist Richard Green of the University of California, Santa Cruz, co-author of the paper.

In 2010, Green helped produce the first draft sequence of a Neanderthal genome. Four years later, geneticist Joshua Akey co-authored a paper showing that modern humans carry some remnants of Neanderthal DNA. Since then, scientists have continued to refine techniques to extract and analyze genetic material from fossils.

“Better tools allow us to ask increasingly detailed questions about human history and evolution,” said Akey, who now works at Princeton and was not involved in the new research. He praised the methodology of the new study.

However, Alan Templeton, a population geneticist at Washington University in St. Louis, questioned the authors’ assumption that changes in the human genome are distributed randomly, rather than clustered around particular hotspots within the genome.

The findings underscore “that we’re actually a very young species,” Akey said. “Not long ago we shared the planet with other human lineages.”

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Follow Christina Larson on Twitter: @larsonchristina

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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

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