Gene Variations for Immune and Metabolic Conditions Have Persisted in Humans for More Than 700,000 Years
The work builds upon genetic discoveries in the past decade, including when scientists uncovered that modern humans and Neanderthals interbred as early humans moved out of Africa. It also coincides with the growth of personalized genetic testing, with many people now claiming that a small percentage of their genome comes from Neanderthals. But, as the eLife study show, humans share much more in common with Neanderthals than those small percentages indicate. This additional sharing can be traced back to a common ancestor of Neanderthals and humans that lived about 700,000 years ago. This common ancestor bequeathed to the Neanderthals and modern humans a shared legacy in the form of genetic variation.
The research team explored this ancient genetic legacy, focusing on a particular type of genetic variation: deletions. Gokcumen says that the “deletions are strange because they affect large segments. Some of us are missing large chunks of our genome. These deletions should have negative effects and, as a result, be eliminated from the population by natural selection. However, we observed that some deletions are older than modern humans, dating back millions of years ago.” The researchers used computational models to show an excess of these ancient deletions, some of which have persisted since our ancestors first learned to make tools, some 2.6 million years ago. Furthermore, the models found that balancing selection can explain this surplus of ancient deletions.
