Only 7% of DNA is unique to humans and not shared by their early ancestors, suggests study

An improved way of comparing humans' DNA with that of their extinct ancestors has enabled scientists to take another step towards distinguishing mankind from them. According to a study published on July 16, in the journal Science Advances, only 7% of our DNA is unique to humans and not shared by other early ancestors. Nathan Schaefer, a computational biologist at the University of California and co-author of the new paper, said, "That's a pretty small percentage." “This kind of finding is why scientists are turning away from thinking that we humans are so vastly different from Neanderthals,” he added.

The study uses DNA from 279 modern people from throughout the world and fossil remnants of now-extinct Neanderthals and Denisovans dating back to roughly 40,000 to 50,000 years ago. Scientists already know that modern humans share some DNA with Neanderthals, but various sections of the genome are shared by different people. One of the goals of the new study was to find genes that are unique to modern people.

Only 1.5 per cent of DNA is shared by all living people

The researchers "developed a valuable tool that takes account of missing data in the ancient genomes," said paleoanthropologist John Hawks, at the University of Wisconsin, Madison, who was not involved in the study. They also discovered that a much smaller portion of the DNA  i.e. just 1.5 per cent is unique to our species and shared by all living people. Those slivers of DNA could offer the most important insights as to what genuinely differentiates modern humans.

Richard Green, a computational biologist at the University of California, Santa Cruz, and a co-author of the article, stated, "We can tell those regions of the genome are highly enriched for genes that have to do with neural development and brain function." Green assisted in the creation of the first draught sequence of a Neanderthal genome in 2010. Geneticist Joshua Akey co-authored a report four years later indicating that modern people have some Neanderthal DNA traces. Scientists have continued to improve ways for extracting and analysing genetic material from fossils since then.

“Better tools allow us to ask increasingly more 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 new study's methods. In contrast, Alan Templeton of Washington University in St. Louis questioned the authors' hypothesis that human genome modifications are randomly distributed instead of clustered around specific geographic areas. According to Akey, the data predicts "that we’re actually a very young species.” “Not that long ago, we shared the planet with other human lineages,” he added.

(With AP inputs)