[MUSIC] Welcome Back. Famously it's become clear from analyzing the Neandarthal genome that they contributed DNA to everyone outside Africa. Aproximmately 2.5% of DNA of those of us outside Africa, derives from Neanderthals. That contribution exists in people in China and India, and places where Neanderthals have never been. Which suggests that these contributions were only made early on when modern humans were coming out of Africa, and that Neanderthals in the Middle East, 65,000, 95,000 years ago. After that, there was no more interbreeding, and that's a bit of a puzzle. A key question is, did this Neanderthal DNA provide us with any useful attributes, and apparently it did. Some of our immune genes are Neanderthal. We weren't adapted to European viruses. Neanderthals were. As we can thank our Neanderthal heritage that when we get a common cold it's not worse than it is. On the other hand Neanderthals lacked certain forms of genes that may help modern humans fight off epidemic diseases such as measles. Possibly the low density populations in Neanderthals may of meant that epidemics were unlikely. So they were probably not benefited from them. Oh okay, let's have a look now at those enigmatic Denisovan's, and this is Denisova cave. This is the entrance to a cave in Siberia for Denisover. Where he found a beautiful bracelet, which took 14 different technologists to make. Nobody had any idea that people in the Paleolithic could make such jewelry. But everyone assumed it must be homo sapiens, us, because we're a speciesist. We take our superiority for granted. Well they found a small finger bone and teeth, and they got sequence data, and everyone was shocked, cuz the DNA was not homo sapiens. It was not Neanderthal. It was someone new. Slightly more related to neanderthals than us. Well we don't have a skull, so we only have the genome to guess what Denisovan's looked like, and that's worth noting that it's the first example of a new human species identified from a genome. The genome is from a girl, and it shows she had dark skin and brown hair with brown eyes. There's about 100,000 recent changes in our genome, which distinguishes us from this Denisova girl, and some of these influenced genes link with brain function, nervous system development, suggesting we may think differently from her, just as we do with the Neanderthals. But Denisovan's also bred with some modern humans. Approximately 5% of the DNA of people in Papua New Guinea derive from Denisovan's. Three more genomes from the Denisova cave were analyzed in 2013, one of them turned out to be a Neanderthal. They analysis of all these genomes paint a complex picture of intermingling amongst ancient human groups. The Neanderthals were inbred with cousins breeding together, but the Denisovans were very diverse, with 70% Neanderthal DNA, there was found mixing between Denisovans and an even earlier mystery species. Well let's think about Africa which is the home of our species, Homo Sapiens. If Neanderthals and Denisovans interbred with people out of Africa. What about those of us who stayed in Africa, or just left Africa recently. Are modern day Africans the only pure bred Homo Sapiens? That's where Albert Perry comes in. Now Albert Perry was an African American who lived in South Carolina. Michael Hemistein recently analyzed his Y chromosome and found it to be so distinct, that it probably separated from all others about 338,000 years ago. We're digging deeper, Hammer's team examined an African database of nearly 6000 Y chromosomes, and they found similarities between Perry's Y chromosomes and those in samples taken from 11 men, all living in one village in the Cameroon. While the first anatomically modern human fossils date back only 195,000 years ago. So their Y-chromosome lineage split from the rest of humanity long before our species appeared. The most likely explanation is that Perry's Y-chromosome, that Cameroon Y-chromosome, was inherited from an archaic human population that has since gone extinct. Well, if that's the case, then sometime within the last 195,000 years, anatomically modern humans interbred with an ancient African human. With all this interbreeding it's hard to talk in terms of defined species, are we really a different species from the archaic common weeds if we produce for tile offspring with them? So rather than a family tree, we have networks of interactions in a world long ago, but if you look for specific genetic changes that underline evolution. You find 31, 000 SNP's not found in the chimp, Neanderthal, and Denisovan genomes, these SNP's led to 96 protein changes and more than 3,000 changes in regulatory regions. So it was 125 small insertions and deletions that are unique to us. But as we discussed before, the trick will be to find out which of these unique genetic changes do things for us. It's possible, even probable that a lot of them do nothing. There have been some recent finds, suggesting that some archaic humans lived very recently. We have the famous hobbits, the Homo floresiensis, living in remote places in Indonesia, and then there's these, the red deer cave people in China, shown here. But the hobbits and these red deer cave people, they're very enigmatic, and the experts differ greatly on how to classify them. The Red Deer Cave people they're the youngest known prehistoric population who don't look like modern humans, fossils date them between 14,500 and 11,500 years old. Having a mixture of archaic and modern features, they're tentatively thought to be a separate species of human, however you define species now, that has become extinct. Attempts to extract DNA so far have been unsuccessful, but they're continuing, and obviously only if this is done is it going to be possible to determine the relationship between this group of other archaic and modern humans. Possibly perhaps, these are the Denisovan's, they haven't been able to get hobbit DNA either, and that emphasizes that any discovery is only as good as the material you have to work with. Little if any of the ancient DNA is likely to have survived the heat and moisture of the tropics, and any that has, may be highly fragmented. The key to getting DNA out that has not totally degraded, are particular kinds of preservation conditions such as haze when it's cold and dark. Often specimens would have been frozen since they got buried. The [INAUDIBLE] goes to a genome sequence from a horse bone frozen for 700,000 years in the permafrost of the Yukon in Canada. However studies with leg bones of an extinct flightless bird called the Moa, suggest that under subzero conditions the last remnants of DNA would disappear around the 6 to 8 million year mark. Potentially therefore, perhaps there's a slight chance we could get some DNA right back to our split from the chimp lineage. Anyway, whatever their relationships with us, all but the bones and tools of the archaic commonites are gone. It took just 10,000 years for modern humans to completely replace Neanderthals when they got into Europe, and judging by this outcome, we were competitively superior to Neanderthals from the others. We don't know what the advantage was, several explanations have been suggested. Some, all of them may be correct. We have projectile weapons, in contrast to the thrusting spears of Neanderthals. What if lightly built modern humans could hunt as well as Neanderthals, while requiring fewer calories, perhaps the strongly built Neanderthals became obsolete. However, recent analysis of dental plaque on Neanderthal teeth has shown they cooked and ate a lot more plant material than was previously realized. So, I think we can say that at least Neanderthals had a balanced diet. Another theory involves the fact that Neanderthals had larger eyes as an adaptation to long, dark European nights. It's been suggested therefore, that a larger section of their brains may have been devoted to maintaining good vision, leaving less room for higher level thinking processes and other functions like social thinking, eventually leading to extinction. However, some modern humans have big eyes and some have small eyes. Have you noticed any link with intelligence? I haven't. Well, clearly Neanderthals rapidly adapted and copied modern human tools, so cognitively they can't have been that far behind us. Another theory which makes more sense to me, is that modern humans may have already had dogs that gave them a competitive advantage. The most popular hypothesis is that modern humans had developed more of advanced language skills, and so could pass knowledge down through generations. Without it, there's very distinct limits to cultural sophistication. While language may have allowed competivations of human tribes to develop. The structure of Neanderthal vocal chords and tongues suggests they couldn't make vowel sounds, but otherwise we have no idea how well they communicated. [SOUND]
