Who Were The Super Archaic Ghost Humans

Inside many ethnic groups in the world today, tiny genetic traces of extinct human species can be found. In non-African populations, between 1 and 4% of our DNA belongs to the long-lost Neanderthals, and in Australasian populations, between 4 and 6% of our DNA can be traced back to the Denisovans. This is visible genetic evidence that our ancestors, thousands of years ago, interbred with archaic humans who were not members of the species Homo sapiens. Certain genetic variations, inherited from our non-Homo sapien forefathers, can influence the way we look and feel today. Our hair texture, our height, sense of smell, the strength of our immune systems, and how we react to high altitudes may all be affected by the amount of Neanderthal or Denisovan DNA that we carry as modern humans. However, as genetic science and research has improved over the years, it has become apparent that some inherited DNA within the modern human genome cannot be assigned to any known population of archaic humans. We know that they existed, as traces of their genetic information can be found in our bodies today, but we have no concrete fossil evidence of who they might have been. These missing pieces of the puzzle are aptly named ghost populations. In some ethnic groups of modern humans, DNA from ghost populations can make up as much as 19% of their genetic makeup. This raises a number of questions, but most prominently, who were these archaic ghost humans that left their genes behind? In today's video, we will be exploring the idea of genetic ghosts in the anthropological record, piecing together the information which we are lucky enough to have at hand. Join us as we take a close look inside ourselves to discover the super-archaic ghost humans who lie so close yet so far. Modern scientists were able to discern in 2012 that the first Americans, the ancient Homo sapiens that crossed over the now sunken Bering Land Bridge between eastern Serbia and western Alaska, were frequently interbreeding with members of another mysterious human population. They discovered this by taking an intricate look at the DNA that sat within the remains of these humans. But without any hard fossil evidence, there was no telling exactly who this mysterious extinct population was, what they looked like, or even where they were from. All they knew was that this chunk of DNA did not match that found in any surviving human population. This is where the term ghost population arose. That was, however, until ancient remains described from Siberia in 2013, whose DNA matched the missing genetic block were found. This proved that archaic, extinct populations of Homo sapiens did exist, and no longer needed to be considered a ghost population. Steadily, however, it would become apparent that other archaic humans had additional missing pieces in their genetic makeup. Ghost populations, it would seem, were present all across the ancient world, and one particularly large population from Eurasia, towards the end of the Pleistocene, continues to keep anthropologists scratching their heads. What's even more interesting, though, is that some of these ghost populations may not have even belonged to the species Homo sapien. Rather, there may have been one or more unknown species, akin to the Neanderthals and Denisovans, that researchers have not yet unearthed. Collectively, these missing humans have been dubbed the super-archaic humans, and may even be older than the Neanderthals and Denisovans themselves, representing relict populations that modern humans encountered potentially just outside of Africa. Ghost DNA has been found not only within Homo sapiens, but also in the remains of Neanderthals and Denisovan specimens, too. In 2014, genetic scientists were able to pinpoint unidentified segments of DNA within the remains of both archaic species that could not be traced to any known population of humans. It is thought that this mystery species may have existed at any point between 900,000 to 4 million years ago, meaning that they may have appeared significantly early on in the overall human timeline. Further genomes from additional Neanderthals and Denisovans were also analyzed in 2020, which provided supporting evidence that this interbreeding with a mystery species did indeed take place. This study also showed that the common ancestors of Neanderthals and Denisovans, casually dubbed the Neandersovans by some scientists, also interbred with the unknown species, which meant that this mystery DNA was carried forward to the Neandersovans' descendants when they split into two. The missing species in question, then, may not have closely resembled Neanderthals, Denisovans, or Homo sapiens, but was basal of all three, having split off from the human lineage much earlier. Still, they were closely related enough to have successfully passed on their genes down to the known human species of the late Pleistocene, and some ethnic groups of modern Homo sapiens still carry this mystery DNA today. At the time this interbreeding took place, humans had already left Africa, as Homo neanderthalensis and Homo Denisova, two species that evolved in Eurasia, were involved in the process. This leads to an intriguing possibility. The super-archaic humans in question may have been a new species that descended from the first population of Homo erectus to leave Africa, 1.9 million years ago. When Homo erectus left the continent for the first time, it would split off into distinct populations, that gradually made their way into Eurasia and Southeast Asia. There were some groups who broke off from this main population, and became resistant to cooler, high-altitude conditions. They would lead to the Neanderthals and Denisovans. Others would travel to the islands of Indonesia, where they would become diminutive, well-equipped to live in dense forests. They would lead to the tiny Homo floresiensis. It is not out of the question that another, even more basal lineage, may have split off from the main Homo erectus crowd as they left Africa, giving way to another undiscovered species that we would one day know only as the super-archaics. When the Neanderthals encountered this group of super-archaic humans, interbreeding would follow, and their DNA found its way into the genetic makeup of the Neanderthals. However, Homo erectus and its offshoots may not be the sole source of this mystery DNA. Genetic analysis seems to support the theory that the interbreeding with the ghost population took place in two waves. The second wave took place after the Neanderthals and Denisovans split apart from one another, possibly after Homo erectus had gone extinct. Could there potentially have been an altogether different group of mystery humans that we're not aware of that could have been responsible for these gaps in our knowledge? Another question to ask when considering the identity of these super-archaics is what happened to them. We know that there were enough individuals alive in the world at the time to have left a clear mark on the DNA of several ethnic groups of modern humans, as well as the extinct Neanderthals and Denisovans. One theory is that as the super-archaics continued to interbreed with Homo sapiens, Neanderthals, and their split descendants, their genome was effectively absorbed as a result. The interbreeding may have been so prolific in places that the line between Neanderthal, Homo sapiens, and super-archaic may have been blurred into one, as genes and traits joined one big melting pot. Neanderthals and Denisovans may have been more prominent and common, and as a result, the populations of super-archaics just couldn't keep up. The very same thing, in fact, is thought to have contributed to the downfall of the Neanderthals around 40,000 years ago, when interbreeding with Homo sapiens effectively absorbed Homo neanderthalensis to extinction. It may turn out that history was simply repeating itself when the Neanderthals were wiped off the face of the Earth. If this hasn't been enough of an anthropological mystery for you, then consider that several ethnic groups of sub-Saharan African humans who are alive today contain the unidentified DNA of an even older species. Some of these modern humans' genetic makeup contains between 2 and a whopping 19% of some mystery archaic DNA, which may have belonged to a human species that was present in Africa before Homo sapiens had left the continent. Again, this DNA belonged to a basal human species, not particularly closely related to Homo sapiens at all. So what exactly was it? The current hypothesis, as of 2020, is that this was a species that split from the common ancestor of Homo sapiens and Neanderthals. This would mean that another separate lineage of humans, distinct from ourselves and our closest evolutionary relatives, was also living in Africa while we were still evolving. But bizarrely, no concrete fossil evidence has been left behind to tell us exactly what this near-human species might have been. These genetic variations have been lost in non-African populations, but are particularly substantial in the African populations they were discovered in. This may indeed mean that a mystery species was present in Africa until relatively very recently, at least recently enough that it was able to interbreed with modern humans living in Africa before they had a chance to migrate out of the continent. It may have been yet another offshoot of Homo erectus that had begun evolving separately to Homo sapiens, or it could be something else entirely, but without the fossil evidence, it's hard to say for certain. That is what makes this genetic phenomenon so intriguing. For hundreds of thousands, perhaps even millions of years, our ancestors were frequently interacting with a species who we now know absolutely nothing about. Every day, their lives may have been shaped by these encounters. They may have even felt love and compassion for members of this mysterious species that has been utterly and completely lost to the depths of time. It's almost mind-boggling to imagine ourselves sharing the planet with another species of humans today, when only Homo sapiens currently exist in the world, but this was very much the reality for our ancestors. Around every turn, areas of the world they had never visited were presenting them with strange new threats, opportunities, technologies, and, it would seem, companions. Human beings actually aren't the only species to have the remnants of ghost populations in their DNA. Mysterious genes have also been discovered in a few species of modern animals too. Most notably, in 2015, a study showed that modern domestic pigs have chunks of DNA belonging to an unknown ghost population that bred with them as they migrated across Eurasia during the Pleistocene. This would indicate that it perhaps wasn't just the wild boar that gave way to the rise of the domestic pig during the early days of human settlement and agriculture. An undiscovered species may have played a pivotal part too. The same can also be said for the grey wolf. In 2018, researchers working on the genome of modern canids discovered that the last common ancestor between the grey wolf and the coyote interbred with a mysterious, unidentified species of prehistoric dog that was likely related to the modern dhole, a species of wild canid from Southeast Asia. Then there are also the countless gaps in the fossil record that serve as missing links between lineages of species. As fossilization is a rare occurrence, not all species have been preserved in sediment, and so huge gaps are often left behind as scientists try to piece together the links between known species. Transitional fossils between species are even rarer, and there are many missing pieces between lineages of ancient mammal, bird, dinosaur, ichthyosaur, invertebrates and more that have simply not been unearthed. There are very few fossils which show, for example, how early lizard-like archosaurs evolved to become the acrobatic winged pterosaurs, the first true aerial masters of the vertebrate world. Likewise, we know very little about how the ichthyosaurs transitioned from land-based quadrupeds to huge marine apex predators, almost entirely resembling fish but over a relatively short space of time. In these cases, it's speculation that often takes over, as researchers attempt to fill in the gaps. Rarely, some modern animals, often considered to be living fossils, face the same problem. Protanguila palau, a species of deep-water cave-dwelling eel, was discovered in 2012, where it was immediately placed not only in its own genus but within its family entirely. Often referred to as the Palauan primitive cave eel, this species has retained features found only in ancient eel species, and is morphologically very different to all of its closest relatives, if you can even consider them that. Scientists think that this fish may have split from all other eel lineages over 200 million years ago, and it has been evolving separately to others ever since. Remarkably, nothing in the fossil record has ever been found to be ancestral to this single eel species in that entire 200 million year period, meaning that its entire natural history to date is something of a ghost. One can only wonder how something so rare has miraculously managed to persist, going under the radar of both paleontologists and biologists, for such a long time. The concept of super-archaic ghost humans is one of the greatest mysteries of the evolution of our species. To think that entire lineages of species may have been lost to the depths of time is a frustrating thought to say the least. It blocks us from truly knowing our own natural history in full. What we can hope for, however, is that modern paleontological technologies and practices will help us to unearth additional specimens of archaic humans over the coming years. Given that there were enough of these humans around to make a lasting imprint on our modern genome, it may not be beyond the realms of possibility to hope for a game-changing fossil discovery.