Denisovan - Ancient Human

a young girl walks along a river the air is cold to the skin in the cool summer months step after step she looks for small shells along the rocks shells which could be made into beautiful jewelry none are found though as she walks back to her home her tribe is preparing a meal a meal of a local deer and various plants scavenged from the area but her home is strange it's a cave a cave full of strange looking people a people with long heads and stocky bodies uniformity lacks within the group itself it seems to be made up of two distinct groups but nevertheless she fits into this odd bunch for her mother is a neanderthal and her father is denisovan a band of different human species unfortunately she would soon die never reaching adulthood though her fate was grim she would leave behind a single fossil for another species of human to find ninety thousand years later she would be named denny a girl only known by a single bone fragment about two centimeters long though not a very impressive find at first sight dna analysis has been able to discover many fascinating things about this fossil dating analysis from 2016 determined that this individual died out about 90 000 years ago the bone fragments characteristics indicate an age of at least 13 years she had survived childhood but perhaps fell sick was wounded or starved to death it was found in the now famous denisova cave located in the denisova valley siberia russia denny lived a very long time ago a time when many species of humans still roam the earth and she herself was a hybrid of two now long extinct species through dna we know her mother was a neanderthal and that her father was denisovan fines such as this show us how complicated the human story really is many different species intermixing to create fertile hybrids which then can mix even more in this new series i will cover every human species currently known in detail the field of paleoanthropology is very complicated and ever-changing many topics are hotly debated and will change and become outdated [Music] today i will cover the mysterious denisovans or homo denisova if i say anything that is factually incorrect or outdated then please correct me down below there's so much to cover so without further ado let's get into it [Music] the first evidence of these long gone hominins was discovered in denisova cave a strange cave that is brimming with history it has been used by people in the region for thousands of years in the 18th century the cave was inhabited by a religious hermit named dennis little did he know his name would eventually become the name for a whole species of human the cave was first inspected for fossils in the 1970s by russian paleontologist nikolai of ovida who was looking for remains of canids so far 22 strata have been identified with archaeological artifacts i cover from the time of dennis back to over 200 000 years ago it wasn't until 2008 that russian archaeologists investigated the cave and found the finger bone of a juvenile female originally dating to fifty to thirty thousand years ago the estimate has since changed to seventy six thousand to fifty two thousand years ago the specimen was originally named x-woman matrilineal mitochondrial dna extracted from the bone demonstrated it belonged to an undiscovered species of hominin genetically distinct from both modern humans and neanderthals a whole sect of humanity unknown until the discovery of a tiny bone more recent dating in 2019 by greek archaeologists katarina duca and colleagues gave further clarity on the age of the specimens found the oldest specimen denisova 2 lived anywhere between 123 and 195 000 years ago quite a wide margin as of now but this date is still important based on artifacts also found in the cave hominin occupation most likely by denisovans began over 280 000 years ago [Music] a common misconception is that homo sapiens were the first to leave africa and conquer the world this is something i once thought and maybe many of you did as well in reality human species called much of europe and asia home long before our kin did interestingly neanderthals were also present 193 and 97 000 years ago likely during the same time as dennis owens denny is dated around 90 to 100 000 years ago so it makes sense that neanderthals would have been there considering her mother was a neanderthal they could have been living there for much longer but those are the only two dates that we currently have caves are great forms of shelter denisova cave is a fairly large cave it is 270 meters squared or 2900 square feet located 700 meters or 2300 feet above sea level it is surrounded by a lush mountainous region a region which is likely relatively the same even today a river flow is only 28 meters below and would have provided clean water and even fish to the cave's inhabitants there is no wonder why people wanted to live here also one hundred thousand years ago the world was colder the earth had still not entered into the last glaciation often called the ice age but the weather was still colder having good shelter was crucial to survival you could imagine hundreds of generations were born lived and died in this cave people starved hyenas attacked and successful hunts were celebrated denisovans were living in this cave long before homo sapiens had even left africa it is also fascinating to think that neanderthals a distinct species lived and likely coexisted with denisovans we know from dna that these hominins were quite different but similar enough that we know they mated and produced viable offspring on numerous occasions about 17 of the denisovan genome is made up of neanderthal dna it is fascinating to think about how they would have interacted currently the fossils of five distinct denisovan individuals from denisova cave have been identified through their ancient dna denisova 2 3 4 8 and 13. denisova 11 is the fossil of denny the hybrid between a neanderthal and a denisovan the actual fossil material consists of a finger bone three molars a partial mandible an arm or leg fragment and a periatrial bone fragment because of such fragmentary evidence much of what we know about these people comes from their dna all these specimens came from denisova cave until 2019 when a research group described a partial mandible discovered in 1980 by a buddhist monk it was discovered on the tibetan plateau in baishia karst cave located in china over 1700 miles away from denisova cave we know that they had quite a large range that included much of asia but a lack of fossil material leaves us with many questions [Music] so what exactly are denisovans where did they come from and how closely are they related to homo sapiens or neanderthals mitochondrial dna extracted from denisova 3 has provided us with answers to some of these questions geneticists can use nucleotide bases of mitochondrial dna to determine how similar animals genetics are with this technique it has found the difference between modern humans and neanderthals is approximately two hundred and two bases out of sixteen thousand five hundred so that would be one point two two percent different denisova three's mt dna differs from that of modern humans by 385 bases so that would be 2. 33 and finally chimpanzees differ by about 1462 bases or 8.

86 percent when looking at these differences it is easy to make the mistake that different means worse or more primitive this is simply not the case in reality denisovans had a lot of unique advantageous adaptations but i will talk about this further in the video denisovans neanderthals and homo sapiens are all related in a very complicated way genesobans and neanderthals mainly evolved in eurasia while homo sapiens evolved in africa their genetic story is so complicated because of many inter-breeding events and a very large geographic range human evolution is in no way linear and instead populations of what we would consider more modern humans would occasionally mate with some more primitive groups when i say modern i mean humans with smaller jaws smaller teeth and bigger brains [Music] pockets of more archaic humans lived all throughout the world along with denisovans neanderthals and homo sapiens and a handful of other species [Music] dna evidence has told us a complicated often contradicting story about when these three groups diverge from each other it is generally accepted that the human lineage diverged from the ancestors of denisovans and neanderthals about 600 000 years ago later around 400 000 years ago denisovans and neanderthals split evidence suggests that denisovans may have been the descendants of an early migration of homo erectus that settled in asia or more likely descendants of homo heidelbergensis that eventually went to asia [Music] it actually might have been a complicated mix of both since denisovans and neanderthals only split around four hundred thousand years ago they were quite similar but since denisovans interbred with more archaea coming in like homo erectus and possibly a yet unknown species they may have had more archaic genes science on how these species are related is very confusing and there is no simple answer to give further research will clarify their relation it got even more confusing when scientists discovered that there may have been even more than one species of denisovan researchers from indonesia's aichikman university as well as from new zealand and singapore collected dna from the 161 modern individuals across the swath of the nation of islands they then compared it to the genomes from other modern-day humans neanderthals and denisovans okay well i just realized i've been saying denisovan this whole time when correctly it's pronounced denisovan so i'm going to be saying that for the rest of the video they use the modern day fragments of denisovan dna to reconstruct what those ancient populations may have looked like the result is a trove of data on the ancient hominins one that substantially deepens our understanding of their lives perhaps the most significant way that the new genetic evidence alters our conception of the denisovans is that it reveals them to be much more diverse in some modern indonesians scientists found not one but two distinct denisovan genomic signatures these two groups also look different from the denisovans previously found in siberia which researchers say was another group altogether this actually explains a lot about why their genetics are so confusing and sometimes contradictory beans spread across so wide an area for so long and interbreeding with modern and archaic accommodates as a reason for their diversification into multiple lineages the three groups were bound by two large geographical barriers the himalayas in the east and the oceanic gaps between the islands that make up indonesia today i say three groups but in reality there might have been more scientists just say at least three groups as researchers see it one group of denisovans would have lived in and around present-day siberia kazakhstan and in china just north of the himalayas and the remains from members of this group are likely what researchers found in 2010 in denisova cave but a different group of denisovans lived in southeast asia around what is now thailand and vietnam the third group called the islands of indonesia home two southern groups diverged from the siberian denisovans over 250 000 years ago that's before anatomically modern humans even appeared and at least one of these groups survived well into the pleistocene dying out just tens of thousands of years ago at least three very distinct tennis open populations were in existence and have contributed to modern human genomes one of the groups that showed up in the papuan's genome actually looked so genetically distinct that murray cox of new zealand's massey universities says they would have likely been considered an entirely new species he said if we are going to call neanderthals and denisovans by a unique name which we do then we should probably call this other group by another name while the researchers cannot name a species without actual fossil evidence cox says that genetically the group living in southeast asia looked as different from denisovans and siberia as it did from neanderthals it just shows how much there is to discover about these hominins i can't wait for some remains of these distinct tenosovens to be found and maybe they will constitute an entire new species i have a feeling that some remains will be found in southeast asia but for now all i can do is hope [Music] another important discovery worth mentioning is an interbreeding event between the ancestors of denisovans and neanderthals and a population of so-called super archaic hominins the newly discovered episode involves interbreeding over 700 000 years ago it happened before denis event and neanderthals split off the super archaic and neanderthal denisovan ancestor populations were more distantly related than any other pair of human populations previously known to interbreed for example modern humans and neanderthals at most had been separated for about 750 000 years when they interbred the super archaics and neanderthal denisovan ancestors were separated for well over a million years four percent of the denisovan genome comes from this unknown archaic human species which diverged from modern humans over a million years ago this sheds new light on just how distantly human populations can be separated and successfully mate modern humans would end up inheriting some of these genes when we interbred with neanderthals and denisovans so what did denisovans actually look like not much is known about the precise anatomical features of these people but we can still tell a lot with the fossils we have the finger bone is similar to the same bone in modern humans in fact it is nearly indistinguishable from homo sapiens in contrast the molars are much different than ours they are large and robust similar to that of middle pleistocene archaic humans the third molar is just outside the range of any homo species except hablis and homo rudolph fences it is more like that of australopithecines the second molar is larger than those of modern humans and neanderthals and is more similar to that seen in homo erectus and habelis this suggests that perhaps their diet consisted of more tough vegetation and unprocessed food they likely had a diverse diet of roots and tubers nuts fruits green resources and meat their jaws were large and powerful to process all this tough food the periatrial bone discovery is reminiscent of that of homo erectus a facial reconstruction of denny has been generated by comparing methylation at individual genetic loci associated with facial structure this analysis suggested that denisovans much like neanderthals had long broad and projecting faces a large nose sloping forehead protruding jaw elongated and flattened skull and a wide chest and hips their bodies were stout like neanderthals and they were likely shorter than modern humans and were well suited for their cold environment their brain size is unknown but it is likely very similar to that of a neanderthal neanderthals had larger brains than homo sapiens but bigger does not mean better denisovans may have had larger brains than us but like neanderthals the volume was used for heightened senses rather than a larger prefrontal cortex they are still not dumb by any means studying intelligence of hominins in the fossil record is extremely hard genes for intelligence and brain volume can be studied but we don't have a skull of a denisovan regardless they were humans with the human capacity to reason and logic they may have even wondered about the same universal questions that we do why are we here where do we come from and what's the point they were not sub-humans or on the border of becoming human they were human remember there are only 385 base pairs away from us out of just 16 500. and you see i use the word different not less just different from genes alone we cannot know how an animal thinks or behaves but if you brought a denisoven to present day it could likely learn the same things that makes us human their genes tell us that they had darker skin how much so we're not exactly sure you could also imagine different groups had different shades of color they also are thought to have brown hair and brown eyes again denisovans were not uniform just look at the diversity in modern humans much different color and other physical attributes denisovans were much more diverse of a species than us like mentioned earlier they may have been multiple species it would be correct to say that these three groups looked much different from each other maybe some had lighter skin to cope with a lack of sunlight in cold environments or maybe some had a pronounced epicanthal fold like seen in modern humans living in asia facial and skeletal reconstructions have been made using genetics and comparing them to neanderthals and homo sapiens overall they were similar to neanderthals but may have looked very different it is unfortunate that we currently have such little fossil evidence of these people however we do have some interesting artifacts that were likely produced by denisovans early middle paleolithic stone cores from denisova cave show us a variety of techniques that were used to process the stone actual tools created during this time include scrapers tenticulate tools and notch tools since it was the early middle paleolithic these tools were very old the oldest deposits were probably older than 287 thousand years ago in the main chamber and 269 thousand years ago in the southern chamber middle paleolithic assemblages predominantly contain side scrapers notched denticulate tools end scrapers burns chisel-like tools and trunnicated flakes these date to 156 thousand years ago in the main chamber and 58 000 years ago in the east chamber in upper paleolithic layers there were very interesting bone tools and elaborate ornaments a marble ring a ivory ring an ivory pendant a red deer tooth pendant an elk tooth pendant a chloride light bracelet and a bone needle however denisovans are only confirmed to have inhabited the cave until 55 000 years ago and the dating of these artifacts overlaps with modern human migration into the relative area it remains unclear what species made these artifacts but it very well could have been denisovans denisovans mated with homo sapiens long ago since they mainly lived in the east their genes are concentrated there southeast asians have the highest degree of denisovan dna a 2011 study found that denisovan dna is prevalent in australian aborigines near oceanians polynesians fijians eastern indonesians and maman wands interestingly it was not found in the same degree in east asians western indonesians jahi people from malaysia or anji from adam adaman islands this tells us that introgression with denisovans occurred mainly within the pacific region rather than on the asian mainland like once thought intragression is the transfer of genetic information from one species to another as a result of hybridization between them and repeated back crossing the melanesian genome about four to six percent or one point nine to three point four percent derives from denisovan introgression new guineans and australian aborigines have the most introgressed dna in pop winds less denisovan ancestry is seen in the x chromosome than autosomes and some autosomes also have less density ancestry which could indicate hybrid incompatibility the former observation could be explained by less female denisovan integration into modern humans or more female modern human immigrants who diluted of an x chromosome ancestry which could mean that homo sapien women were seen as more attractive to not only homo sapiens but perhaps to denisovans as well denisovan ancestry and mainland asians and native americans was only about 0.