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Michael Smeltzer and Deborah Brewington, Vanderbilt University
Michael Smeltzer and Deborah Brewington, Vanderbilt University

Having Neanderthal DNA May Increase Your Risk of Certain Diseases

Michael Smeltzer and Deborah Brewington, Vanderbilt University
Michael Smeltzer and Deborah Brewington, Vanderbilt University

How far back do you know your family’s medical history? All the way back to your grandparents? Your great-grandparents? Scientists are looking much farther back, at prehistoric peoples. And one research team has a pretty mind-blowing theory about an influential factor on some modern people’s genes: Neanderthal DNA. The researchers presented their findings today in Washington, D.C. at the annual meeting of the American Association for the Advancement of Science, and have also published a report in the journal Science.

Recent advances in biotechnology have given scientists access to the genetic material of Neanderthals and other pre-modern Homo species. Comparison of their DNA with that of modern humans revealed that around 50,000 years ago, early Eurasian humans and the Neanderthals were … fraternizing. As a result, modern humans with Eurasian ancestry possess about 2 percent Neanderthal DNA. Just what that percentage is and how it relates to the rest of your genes varies from person to person.

Researchers wondered how being part Neanderthal might affect modern humans. They suspected that interbreeding with Homo neanderthalensis must have given early humans some sort of genetic advantage.

“Neanderthals had been living in central Asia and Europe for hundreds of thousands of years before our ancestors ever arrived in these regions,” co-author Tony Capra said at the meeting this morning. “Thus, they had likely adapted to the distinct environmental aspects compared to Africa, such as the climate, plants and animals, and pathogens.”

Those helpful adaptations, Capra continued, would have been passed along to any human newcomers born of Neanderthal-human unions. This human/Neanderthal admixture, as scientists call it, may have made those humans more likely to survive.

“Perhaps spending a night or two with a Neanderthal was a relatively small price to pay for getting thousands of years of adaptations,” Capra said.

To test this hypothesis, the researchers analyzed genetic data from both Neanderthals and modern humans. They compared more than 28,000 anonymous patient health records with known Neanderthal genetic variations.

What they discovered was surprising. The scientists did find evidence that Neanderthal genes may have benefited early humans. But those genes may have outlasted their welcome. The results showed that Neanderthal genes can actually be detrimental to modern humans of Eurasian descent, potentially raising their risk for 12 different medical conditions, including depression, nicotine addiction, and heart attacks

But that revelation comes with a lot of caveats. For starters, the risks, like the genes that present them, vary from person to person. Clearly not all humans with Eurasian ancestry are at high risk for all 12 diseases. Second, the influence of the Neanderthal DNA on risk is both variable and minimal. Having Neanderthal forebears “by no means dooms us to have these diseases,” Capra noted at the meeting.

These results also do not mean that Neanderthals or early humans had these diseases, Capra continued. “Just because the DNA causes problems in our modern environment doesn’t mean it was detrimental in a very different environment 50,000 years ago.” Look at nicotine addiction, for example. Prehistoric people didn’t even use tobacco.

“What our results are saying,” Capra elaborated, “is not that the Neanderthals were depressed, or that they’re making us depressed. It’s that we find that the bits of DNA we inherited from Neanderthals are having an influence on these [body] systems. What that effect is remains to be seen.”

It’s also important to note that these results were derived from patient data—that is, people who were already having medical issues of one kind or another. Speaking at the meeting, co-author Corinne Simonti noted that it’s also possible that Neanderthal DNA is still helpful in some way. “Just because [it] negatively affects risk for disease doesn’t mean it’s not protective for other things,” she said.

“Ultimately,” said Capra, “we hope that our work leads to a better understanding of how humans evolved, and how our recent evolutionary history influences how we get sick.”

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All of Your Teeth Evolved From a Single Ancestral Tooth in the Age of the Dinosaurs
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iStock

Anyone who's received a root canal or a lecture from their dentist about flossing probably doesn't appreciate their teeth like they should. But our pearly whites are unlike any other structures in the body, and for that, they deserve some recognition.

In their new video, TED-Ed explains what exactly makes teeth unique. Unlike regular bones, teeth are made of two layers: a hard enamel coating and a strong dentin core. The combination of these two components makes teeth both hard and strong enough to endure a lifetime of wear and tear.

The tooth's tough composition isn't exclusive to humans. All mammals, whether they're meat-tearing cats or grass-munching cows, grow their teeth the same way, and they owe their teeth's existence to a common ancestor.

In the 19th century, paleontologist Edward Drinker Cope hypothesized that the tribosphenic molar, a tooth type that evolved during the dinosaur age, is the root of all modern mammalian teeth. With just a few genetic tweaks made over millennia, the tribosphenic molar has given way to the teeth used by carnivores, herbivores, and omnivores to process their food.

To learn more about the evolution and biology of teeth, check out the video from TED-Ed below.

[h/t TED-Ed]

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Stones, Bones, and Wrecks
The Most Complete Fossil of an Early Human Relative Goes on Display
AFP, Stringer, Getty Images
AFP, Stringer, Getty Images

Twenty years after it was discovered in an African cave, one of the most important fossils in the quest to demystify human evolution is finally on display. As Smithsonian reports, Little Foot, an Australopithecus specimen dating back more than 3 million years, was revealed to the public this month at the Hominin Vault at the University of the Witwatersrand’s Evolutionary Studies Institute in Johannesburg, South Africa.

Paleontologist Ron Clarke discovered the first bone fragments from the fossil in 1994. The pieces came from the remains of a young female’s feet, hence the nickname. Clarke and his team spent years excavating Little Foot bit by bit from the Sterkfontein cave system in South Africa until the bones were fully removed in 2012. The shattered remains had been embedded in a concrete-like material called breccia, making them incredibly tricky to recover. But the sum of the parts is monumental: Little Foot is the most complete Austrolopithecus fossil known to science.

The hominid genus Austrolopithecus played an essential early role in the chain of human evolution. Lucy, another famous hominid fossil, is a member of the same genus, but while Lucy is only 40 percent complete, Little Foot retains 90 percent of her skeleton, including her head. It’s also possible that Little Foot surpasses Lucy in age. Most paleontologists agree that Lucy lived about 3.2 million years ago, while one analysis places Little Foot’s age at 3.67 million years.

Austrolopithecus is believed to have spawned Homo, the genus that would eventually contain our species. The discovery of Lucy and other fossils have led scientists to designate East Africa as the cradle of human evolution, but if Little Foot is really as old as tests suggest, then South Africa may deserve a more prominent point in the timeline.

Following Little Foot’s public debut, the team that’s been studying her plans to release a number of papers exploring the many questions her discovery raises.

[h/t Smithsonian]

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