Study Casts New Light on Diseases We Inherited from Neanderthals
Feeling depressed? Can’t kick the tobacco habit? Sun causing skin lesions? Allergies bothering you? Some people of today may blame their Neanderthal ancestry in part for some of these health problems, new studies say.
Scientists announced in 2010 that modern humans share 1 to 4 percent of their DNA with Neanderthals. While we inherited some traits that are no longer helpful, other Neanderthal traits have boosted our immune system and also positively affected our neurology and psychology.
Researchers from Vanderbilt University in Tennessee analyzed medical records of 28,000 patients and found that troglodyte genes may make some people more susceptible to depression, skin lesions, tobacco use, and other ills.
“Our main finding is that Neanderthal DNA does influence clinical traits in modern humans: We discovered associations between Neanderthal DNA and a wide range of traits, including immunological, dermatological, neurological, psychiatric and reproductive diseases,” John Capra, senior author of the paper published in the Feb. 12 issue of the journal Science, told the Vanderbilt news service . Dr. Capra is an evolutionary geneticist and assistant professor of biological sciences at Vanderbilt University.
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It’s not entirely news that some Neanderthal genes have had an adverse effect on the health of Homo sapiens. A previous study found that while the ancient genes may have boosted the immune system, they also may have made some people more susceptible to allergies.
In this video, Professor Tony Capra discusses the study he and his colleagues did.
Dr. Capra and his colleagues found that:
“Neanderthal DNA affects cells called keratinocytes that help protect the skin from environmental damage such as ultraviolet radiation and pathogens. The new analysis found Neanderthal DNA variants influence skin biology in modern humans, in particular the risk of developing sun-induced skin lesions called keratosis, which are caused by abnormal keratinocyte.”
And a small piece of Neanderthal DNA, they found, significantly raises the risk for nicotine addiction.
One part of their study was ambivalent. They found that a number of Neanderthal genes that we inherited affect the risk for psychiatric issues such as depression, some negatively and some positively. “In fact,” the press release states, “a number of snippets of Neanderthal DNA were associated with psychiatric and neurological effects.”
Neanderthal genes have been connected to many health issues in modern humans. ( Deborah Brewington/Vanderbilt University )
The researchers speculated that modern humans coming out of Africa about 40,000 years ago encountered different germs and sunlight levels, and may have picked up adaptive features from the Neanderthals, who probably left Africa much earlier, around 400,000 years ago. But these traits may longer be beneficial in today’s world.
An example is a Neanderthal variant that makes blood coagulate more. Then, it could have sealed wounds more quickly and kept out pathogens or germs. But now the gene causes hypercoagulation and increases risk for strokes, pregnancy complications and pulmonary embolism.
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Ancient Origins reported in 2015 that our close cousins the Neanderthal and Denosivan people interbred with Homo sapiens and gave us genes that help us fight off infections, according to two studies. Unfortunately, those same genes that boosted our first-line immune response may have also made modern people more susceptible to allergies.
Modern humans inherited genes from Neanderthals and Denosivans, two archaic species new extinct. ( Cicero Moraes/CC BY SA 3.0 )
A paper published in The American Journal of Human Genetics says that other studies have found that modern human immunity was boosted by interbreeding with what the authors call “archaic humans.” The genes the authors studied, human toll-like receptors, were possibly passed down to modern humans when they and Neanderthals interbred around 50,000 years ago.
Furthermore, Dr. Michael Dannemann et. al., wrote that the three human toll-like receptor genes in modern people that help us fight disease are among the top 1 percent of genes with the highest Neanderthal introgression. Introgression is the movement of genes from one species to another.
Researchers have estimated that 1 to 6 percent of modern Eurasian genes came from now extinct hominins, including the Denosivans and Neanderthals. The study says other scholars have found that Neanderthal genes boosted the adaptive immune system, but these TLR receptor genes have given us an enhanced ability to fight infections through the innate immune response. The innate immune system is a first line of defense against pathogens and also detects germs and helps activate the adaptive immune response system.
Thus, the effects of homo sapien and “archaic human” interbreeding has both helped and hindered our health in the modern world.
Featured image: The new study says that Neanderthal DNA influences many physical traits in people of European and Asian heritage. Source: Michael Smeltzer, Vanderbilt University
By Mark Miller