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.