Neanderthals and modern humans once interbreed, which may have led to risks for heart attacks, depression, obesity, and nicotine addiction in people today, according to a new study.
John Capra, senior author of the study and an evolutionary geneticist at Vanderbilt University in Nashville, said that Neanderthal DNA influences a lot of traits that are related to disease risks in modern humans; it also has a significant impact on modern human biology. Nowadays, people of European ancestry have about 1.5 to 2.1 percent DNA of Neanderthal origin, he added.
For the new study – published on Thursday (Feb. 11) in the online journal Science – the researchers first found approximately 135,000 Neanderthal genetic variations that exist in modern humans (species: Homo sapiens; subspecies: Homo sapiens sapiens). Then, they looked at data from the Electronic Medical Records and Genomics (eMERGE) Network on more than 28,000 adults in the United States of European ancestry.
The data from eMERGE, which is a consortium of nine hospitals in the U.S., helped the researchers find whether the people in the study had ever received treatment for medical conditions like depression, heart disease, and arthritis. They were also able to determine the Neanderthal genetic variants of each person.
The results showed that Neanderthal genetic variants were linked with a higher risk of twelve traits, like artery thickening and heart attack. According to Capra, he and his colleagues also found that the increased risk of modern humans for nicotine addiction was also linked with a Neanderthal genetic variant; but that does not mean that Neanderthals smoked tobacco, Capra explained.
Some of the Neanderthal genetic variants also appeared to influence the risk of depression in modern humans, Capra and his colleagues said.
Corinne Simonti, lead author of the study and a graduate student of human genetics at Vanderbilt University, stated that the brain is extremely complex and introducing changes from a different evolutionary path might negatively impact it.
According to the researchers, some Neanderthal genetic variants may have helped modern humans when they first moved out of Africa, but those variants might have become harmful later on. For instance, the variant that increases blood clotting can help heal wounds, but it can also increase the risk of miscarriage, stroke, as well as other problems, the researchers said.
The difference in skin colours in modern humans might not be linked with Neanderthal DNA, the researchers suggested. Capra said that those differences likely developed a lot more recently.
Image Source: national geographic