When you think of a Neanderthal, you probably imagine a stoop-shouldered, slobbery caveman dragging a club in his primitive wake. However, recent findings exploded that popular myth -- and, in fact, DNA analysis revealed that Neanderthals were indeed similar enough to humans to interbreed with them, and now all non-Africans can credit Neanderthals with 1 to 4% of their own genes.
Big deal, so you're a tiny bit Neanderthal; everyone's got an uncle or cousin who might qualify, right? Well, that 1 to 4% turns out to be a pretty influential minority, with links to depression, ADHD, a fondness for tobacco, and poor physical fitness. So while Neanderthals aren't around anymore, there are ways they continue to affect your health -- and understanding the implications of humans' Neanderthal side could help decode the mysteries of mental illness.
Calling someone a Neanderthal became a well-known stand-in for an unrefined idiot.
Neanderthals: not as stupid as they look!
Early depictions of a Neanderthal man portrayed a hunching brute with a heavy brow, and German biologist Ernst Haeckel went so far as to suggest the name Homo stupidus. Scientists settled on the kinder Homo neanderthalensis. Still, the early image of Neanderthals persisted to the point that calling someone a "Neanderthal" became a well-known stand-in for an unrefined idiot.
All that changed in 2010, when researchers successfully mapped the Neanderthal genome, which was reinforced by the complete sequencing of a Neanderthal woman in 2014. The result was the discovery that all modern humans with ancestors who had migrated out of Africa had Neanderthal DNA, which means that Neanderthals and early humans were definitely partying together a little more than 40,000 years ago. And "partying" is the scientific term for "having sex."
What your Neanderthal heritage means for your health
So far, scientists have discovered links between Neanderthal genes and more than a dozen modern human traits, the most intriguing of which are depression and nicotine use.
These sorts of connections highlight the sort of speculative scientific work that comes with genetic studies. For example, could a Neanderthal propensity to develop dry, patchy skin after years of solar exposure mean that their descendants somehow don't get enough vitamin D from the sun? We know that a lack of sun exposure is correlated with depression, so maybe the two are connected.
Even stranger is the link to tobacco use, which you know from basic history doesn't make too much sense, since tobacco was exclusively a New World crop before the colonization of the Americas by Europeans. Were mood disorders simply more common among Neanderthals, and if so, why?
Don't blame Neanderthals and call it a day
What scientists do know is that the link is there, though to say that Neanderthal genes cause depression is grossly simplistic. For starters, the idea of depression as an illness wouldn't have existed many millennia ago, though you can imagine the sadness that would ensue if a lovesick Neanderthal didn't land that highly desirable Homo sapiens sexual partner.
"Be careful who you interbreed with."
There's also a separate theory that, far from being restrictive, psychiatric ailments like anxiety and depression actually evolved as adaptive traits. In this model, anxiety over what animal is planning to attack you, or depression over the fact that you haven't found food for a few days, both help rouse you into action and maintain focus on the problem. Happy-go-lucky Neanderthals, in other words, were more likely to be dead Neanderthals -- a trait that would also be valuable in modern humans. The legacy of these hyper-aware Neanderthals may lie in the fact that people prone to severe worry and rumination often have higher verbal intelligence levels than their more carefree counterparts.
So the bottom line is that while you may have early free-loving humans to thank for an elevated depression risk, targeting that genetic legacy to develop potential treatments is still a long way off. In the meantime, the lesson, as always: be careful who you interbreed with.
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