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Hank Green: Scientists might seem like the only group of people in the world who aren't really into a good gossipy sex scandal, but that, in fact, my friends, is not true at all. They love to talk about sex, 'specially when it's the sex lives of our prehistoric ancestors. [intro music] So, scientists are currently gossiping up a storm about the fact that, uh, our early ancestors, the first homo sapiens, may have interbred with some other species, which is weird. It's long been accepted by the scientific community that homo sapiens like me (and probably you) originated in Africa around 200,000 years ago. As far as we can tell, they stayed there for about 140,000 years until they started to get frisky and struck out into the unknown, and one of the things that those adventurous humans discovered out there in the wide world was an older, more primitive, bigger boned species of great ape that we call neanderthal. You may call them "neanderthals" [with a soft "th"], but we in the scientific community call them "neanderthals" [with a hard "t"], because that's what they called themselves. Actually, it's because that's what the cave where their first fossils were found was called. It was in Neanderthal, not Neanderthal. It's just how they spell it. Neanderthals are of course related to humans, but their evolutionary lines had split about 350,000 years before. But just because neanderthals and humans were not the same species, did that prevent them from getting it on? No. And it appears that we were similar enough species that we were actually able to create offspring. Studies have shown that, despite the fact that neanderthals went extinct about 40,000 years ago, they live on in us. According to this research, between 1 and 4 per cent of human DNA is actually neanderthal DNA, so you might as well unstitch your family crest from your smoking jacket. But neanderthals might actually not be the only ancient hominids that humankind had intimate relations with. The recently-discovered denisovans, which probably shared more in common with neanderthals than with humans, are showing up in the genome of people all over southeast Asia, so it turns out that we had a lot more choices of people (or, you know, sort of people) to mate with back in the olden days. But we're not done messing with your conception of what humanity is yet, because it turns out that some of your ancestors may in fact have had sexy times with gorillas. The reason they think this is not to do with our genome; it's to do with the genome of lice, and stick with me, because yeah, I bet you're probably clicking away from the video right now. So, most species of mammals have, uh, one species of lice that's specific to them -- it lives on them and only them, but all over them. Now, humans are a little different. Because we have isolated pockets of hair, we actually have two species of lice -- we have head lice and we have pubic lice. And that's different from every other mammal's lice. But out public lice is very very surprisingly and upsettingly similar to the species that lives on gorillas. Nooo, God, no! Why did we even look into this‽ But, uh, even if our ancestors were having sex with the ancestors of gorillas, which hopefully they weren't (I'm still keeping that as a possibility in my mind), it probably was happening something like 3.3 million years ago, so you probably don't have to run straight to the shower and scrub your skin off with a pumice stone at the moment. But still, dang, Australopithecus, you dirty dog. If you ever wanna watch an episode of SciShow again, and I understand if you don't, but if you do, please subscribe, and you will be able to learn more horribly disturbing facts like the ones that we learned today. Also, if you have questions or comments or ideas for other episodes of SciShow, you can get in touch with us on Twitter and on Facebook and of course in the YouTube comments below, where we will always be happily answering questions. We'll see you next time. [outro music]