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Michael Smeltzer and Deborah Brewington, Vanderbilt University

Having Neanderthal DNA May Increase Your Risk of Certain Diseases

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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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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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YouTube

At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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Animals
The Science Behind the Urge to Cuddle Cute Babies
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iStock

You don’t have to be a cat person to feel your heart warm up at the sight of a big-eyed, tiny-nosed kitten stumbling across the floor. When confronted with a baby kitty, you may feel the urge to scoop it up and cuddle with it for the rest of the day. This reaction isn’t limited to felines—puppies and even some adult animals trigger these same snuggle instincts. If this feeling sounds familiar, that means your brain is just doing what it evolved to do to preserve the human species.

This episode of the National Geographic video series We’re Wired That Way lays out what's going on in your head when you see something cute. The facial features of most young mammals fall into the same configuration: large round eyes, and small noses, mouths, and chins. This is called kinderschema, and humans are engineered to find it adorable because it can be found in our own babies. When we see a typical baby face, it activates our instincts to nurture and protect while also releasing the feel-good chemical dopamine to reward us for doing so. That way we feel driven to keep babies safe even if they’re not our own, thus boosting their chances of survival and the survival of our species.

Because kinderschema isn’t limited to the human race, we feel this response when looking at non-human baby animals as well. Some mammals, like cats and guinea pigs, retain their kinderschema into adulthood. So next time you let out an involuntary squee at the sight of your pet, remember that you have biology to blame.

[h/t National Geographic]

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