Hank Green: There are a bunch of cross-species hybrids out there -- mules, ligers, zebroids, beefullo, we recently discussed the majestic grolar bear.... But we tend to think of humans on a different level from that. We're human! There's no species even close to us! How could we possibly interbreed with something? Also, ewww! But guess what? It's been done, and some say it could be done again. [intro music] It's been done because we all have a little bit of neanderthal in us, as we've discussed previously on SciShow. The average European is 1-4% neanderthal, so in effect we are all interspecies hybrids, though that DNA has become so ingrained in our species that basically it's part of what makes us human. But the more frightening and fascinating question to ask is, "Could it happen again?" Many have asked, and some have even had the urge to try to discover whether it is possible to interbreed humans and our nearest genetic relatives, chimpanzees. Now, before we proceed any further let's be clear that the official position of SciShow and hopefully of humanity is that this is a terrible idea. It is deeply immoral. The creation of a potentially sentient organism, likely with many genetic disorders, who is the only member of his or her species so that we can study it for science is bad and wrong and pretty much the definition of evil. But it is nonetheless a fascinating thing to discuss, as long as we're not actually thinking about doing it. So, first, is it possible? Well, humans and chimps do share a lot of DNA. They do have one more pair of chromosomes than humans, but different numbers of chromosomes isn't an absolute barrier to interbreeding. In fact, there are some species where individuals within that species have different numbers of chromosomes and they manage just fine, a condition known as chromosomal polymorphism. In fact, in 2010 a perfectly normal, fertile Chinese man was discovered to have only 22 chromosome pairs. In the end, the genetic difference between a human and a chimpanzee is roughly the same as the genetic difference between a horse and a zebra, and zebra-horse hybrids happen all the time. A quick note on terminology here -- when geneticists create these name mash-ups, which they actually do for hybrid animals, they put the father first in the portmanteau and the mother second, so if it's a male chimpanzee and a female human, that's a chuman, and it it's a male human and a female chimpanzee, that's a humanzee or a manpanzee. Yeah, man-pansy. In 2006, genetic research suggested that after the last common ancestor of humans and chimpanzees, which lived between 5 and 7 million years ago, there was interbreeding between the human and chimpanzee lineages for 1.2 million years. That's not that surprising, since those lineages would likely have been very similar and living in the same geographies, but it was a bit of a shock to paleoanthropologists when the news broke. There's no evidence, however, of recent human-chimpanzee hybrids, though not for lack of trying. In the 1920s, a Soviet biologist Ilya Ivanov implanted his own sperm into a number of apes including chimpanzees and orangutans. Even more creepily, he attempted to inseminate human volunteers with ape semen. But the good news is, he was never able to do that; the bad news is, it was because all of his primate test subjects had died, likely due to being severely mistreated. Ivanov's research never resulted in a pregnancy of any kind, and eventually his research came under scrutiny, somewhat unsurprisingly. The government freaked out and exiled him to Kazakhstan, and he died there a couple years later. That terrible research is the extent of what we know for sure about whether human-chimp hybrids are possible, and with luck it's the most we will ever know for sure. Whether or not it can be done, I hope we can all agree that it shouldn't. Thanks for watching this episode of SciShow. If you have any questions or comments or suggestions for us, you can find us on Facebook and Twitter or down in the comments below, and if you wanna keep getting smarter with us here at SciShow, you can go to youtube.com/scishow and subscribe. [outro music]