Washington. What makes human beings unique? Scientists took a new step toward solving that old mystery with a tool that could allow accurate comparisons between the DNA of modern humans and that of our extinct ancestors.
Only 7% of our genome is shared exclusively with other humans and not shared with our ancestors, according to a study published Friday by the journal Science Advances.
“It is a very small percentage”, He said Nathan Schaefer, a computational biologist at the University of California and a co-author of the study. “This kind of discovery is why scientists are leaving behind the idea that we are very different from Neanderthals.”
The study uses DNA extracted from Denisovan hominid and Neanderthal fossil remains that date between 40,000 and 50,000 years ago, as well as DNA from 279 modern humans from around the world.
Scientists already know that modern man shares DNA with Neanderthals, but different people share different parts of the genome. One goal of the new studies was to identify genes that are unique to modern humans.
It’s a difficult statistical problem, and the scientists “developed a valuable tool that takes into account missing data in ancient genomes,” he said. John Hawks, a paleontologist at the University of Wisconsin who was not involved in the study.
The scientists also discovered that an even smaller fraction of our genome – 1.5% – is unique to our species and shared by all humans today. Those sections of DNA may contain the most significant clues about what really sets modern humans apart.
“We can identify that these regions of the genome are highly enriched with genes that have to do with neural development and brain function,” he said. Richard Greene, a computational biologist at the University of California, Santa Cruz campus, who is one of the study’s authors.
In 2010, Green helped produce the first preliminary sequence of the Neanderthal genome. Four years later, the geneticist Joshua Akey he co-wrote a study that showed modern humans have traces of Neanderthal DNA. Since then, scientists have continued to refine techniques for extracting and analyzing genetic material from fossils.
“Better tools allow us to ask more and more detailed questions about human history and evolution”said Akey, who now works at Princeton University and was not involved in the study. Akey praised the study’s methodology.
However, Alan Templeton, a population geneticist at the University of Washington, San Luis campus, questioned the authors’ assumptions that changes in the human genome are randomly distributed, rather than clustered around certain axes within the genome.
The findings emphasize “that we are a very young species”said Akey. “Not long ago, we shared the planet with other human lineages.”