In marked contrast to the childish creationist notion of a single founder couple being magically created without ancestors 6-10,000 years ago, evidence is growing that one ancestral species that contributes some of its DNA to modern non-African humans, the Denisovans, were once widespread especially in Southeast Asia and may have reached South America, or at least people carrying some Denisovan DNA may have done, but not via the traditional route - Siberia, Beringia and Alaska - followed by later Homo sapiens.
My understanding is that they and Neanderthals were most likely direct descendants of H. erectus that migrated out of Africa some 2 million years ago and gave rise to the Denisovans in Eastern Eurasia and Neanderthals in Western Eurasia. These two then interbreed with the H. sapiens migrants as they came up out of Africa and spread throughout Eurasia and down to Melanesia, Austronesia and Oceania.
So, rather than a single ancestral couple magically created out of dirt, without ancestors, as creationists believe, modern non-African humans don't have an ancestral couple, they don't even have a single ancestral species but are the result of hybridization between at least three ancestral species.
There is also evidence, according to two researchers from Trinity College, Dublin, Ireland, that there may have been several regional populations of Denisovans, each of which contributed to the Homo sapiens genome at different times. As with other hominin species, they were diversifying as they spread in what may have been the beginnings of classical allopatric speciation.
The Denisovan DNA that was retained by H. sapiens as they migrated into the different environments in Asia was that which gave them an advantage, such as the ability to survive in the low oxygen partial pressure of the Tibetan Plateau - something that the Tibetans have inherited - immunity to certain endemic pathogens and an improved ability to keep their body temperature up during cold weather by burning stored body fats - something that Innuits have inherited.
Tell me all about the Denisovans and why they haven't been given a scientific name yet. The Denisovans are an extinct group of archaic humans who lived during the Pleistocene epoch, primarily known through DNA evidence and limited fossil finds. They were first identified from a small fragment of a pinky bone discovered in 2008 in the Denisova Cave in Siberia, which gave them their informal name. What’s fascinating about Denisovans is their genetic connection to both Neanderthals and modern humans, with traces of Denisovan DNA found in present-day people, especially in populations in Southeast Asia, Oceania, and parts of East Asia.Sadly, what little we know of these archaic hominins is from the DNA extracted from a finger bone found in the Denisova cave in the Altai mountains of Siberia and from a few other fossil fragments including a jawbone recovered from the Tibetan plateau. Other information comes from finding traces of their DNA in the genomes of modern populations
The reason Denisovans haven’t yet received a formal scientific name stems from the limited physical evidence available. To assign a distinct species name under the Linnaean system, scientists traditionally rely on substantial fossil material that can illustrate unique anatomical characteristics. So far, only a few small bones and teeth from Denisova Cave and, more recently, a jawbone from Tibet have been attributed to Denisovans. These fossils, while critical, don’t provide a comprehensive enough picture of Denisovan anatomy to confidently distinguish them as a separate species within the genus Homo.
Genetic analysis has confirmed that Denisovans were a distinct lineage from both Neanderthals and modern humans, suggesting they could merit a unique species name. However, because Denisovan DNA has shown close genetic ties to Neanderthals—along with evidence of interbreeding with early modern humans—paleontologists remain cautious about assigning a new species name until more complete skeletal remains are found.
Have we any clues as to their distribution and lifestyle?
Yes, we’re gathering clues about Denisovan distribution and possible lifestyle from their genetic legacy, fossils, and the few archaeological sites linked to them. Although physical Denisovan remains have only been found in Siberia and Tibet, their genetic traces are surprisingly widespread, indicating a much broader range across Asia and possibly even into Southeast Asia and Oceania. The highest levels of Denisovan DNA in modern populations are found among Melanesians, Australian Aboriginals, and some Southeast Asian groups, suggesting that Denisovans once occupied a vast area.
Clues to Distribution:Clues to Lifestyle:
- Denisova Cave, Siberia: This site provides the most direct evidence of their existence and suggests Denisovans adapted to cold, mountainous environments.
- Tibetan Plateau Jawbone: A Denisovan jawbone found in Baishiya Karst Cave on the Tibetan Plateau suggests they lived at high altitudes and had genetic adaptations to low-oxygen environments. This discovery extends their known range over 1,500 miles from Denisova Cave.
- Genetic Legacy in Southeast Asia and Oceania: High levels of Denisovan ancestry in modern populations like Melanesians suggest they once occupied a wide swath of Asia, possibly reaching as far as islands in the Pacific.
Denisovans likely had a mix of traits allowing them to survive in diverse environments, from high-altitude plateaus to tropical islands. However, without more fossil evidence, much of Denisovan life remains speculative. The DNA evidence we do have hints that they were versatile, likely adapting to varied landscapes and climates.
- Tool Use and Cultural Artifacts: Stone tools and artifacts from Denisova Cave indicate that Denisovans used sophisticated tool-making techniques similar to Neanderthals. They likely hunted large animals and had the knowledge and resources to survive in cold, challenging environments.
- Genetic Adaptations: The Tibetan Plateau jawbone contains the EPAS1 gene variant, associated with high-altitude survival, which suggests that Denisovans might have adapted to specific, challenging habitats, including those with low oxygen levels.
- Interbreeding and Interaction with Other Humans: The presence of Denisovan DNA in various modern human populations suggests they likely interacted and interbred with both Neanderthals and Homo sapiens. This interaction might imply a relatively mobile or wide-ranging lifestyle, allowing contact with other hominin groups.
A recent claim is that they may have reached South America. Do you have any information about that?
Recent findings suggest Denisovan ancestry in some ancient South American populations, adding complexity to the understanding of early human migrations. Researchers have identified Denisovan and Neanderthal DNA in remains from Brazil, Panama, and Uruguay, hinting at possible Denisovan-related migrations into South America that might have occurred independently of the well-known migrations from Asia through Beringia. This genetic signature dates back as far as 40,000 years and has been observed in remains up to 1,500 years old, especially along South America's Atlantic coast.
Additionally, some samples also contained Australasian genetic markers, found in Brazil and Panama but not in ancient North American populations, which might indicate a migration path that bypassed North America. This suggests that early migrations to South America could have followed a unique trajectory, potentially involving coastal routes or unexpected intermingling with Denisovan-related groups.
The discovery of Denisovan DNA in these populations, especially in greater proportion than Neanderthal DNA in some cases, underscores the genetic diversity of early human populations in South America and may challenge existing theories on early human dispersals into the Americas. Ongoing genetic studies are crucial to refining these migration models and understanding the legacy of Denisovan genes among South American indigenous populations today.
Source:
Dr Ongaro and Prof. Emilia Huerta-Sanchez of the Smurfit Institute of Genetics, Trinity College Dublin, Ireland have recently published a review of what we know of the Denisovans so far in Nature Genetics. Sadly, the article is behind a paywall, so we only have the abstract and the press release from Trinity College:
New insights into the Denisovans – the new hominin group that interbred with modern day humans
Scientists believe individuals of the most recently discovered “hominin” group (the Denisovans) that interbred with modern day humans passed on some of their genes via multiple, distinct interbreeding events that helped shape early human history.
In 2010, the first draft of the Neanderthal genome was published, and comparisons with modern human genomes revealed that Neanderthal and modern humans had interbred in the past.
A few months later, analysis of a genome sequenced from a finger bone excavated in the Denisova cave in the Altai mountains in Siberia revealed that this bone fragment was from a newly discovered hominin group that we now call Denisovans, who also interbred with modern humans.
Each of these presents different levels of relatedness to the sequenced Altai Denisovan, indicating a complex relationship between these sister lineages.This was one of the most exciting discoveries in human evolution in the last decade. It’s a common misconception that humans evolved suddenly and neatly from one common ancestor, but the more we learn the more we realise interbreeding with different hominins occurred and helped to shape the people we are today.
Unlike Neanderthal remains, the Denisovan fossil record consists of only that finger bone, a jawbone, teeth, and skull fragments. But by leveraging the surviving Denisovan segments in Modern Human genomes scientists have uncovered evidence of at least three past events whereby genes from distinct Denisovan populations made their way into the genetic signatures of modern humans.
Dr Linda Ongaro, first author Smurfit Institute of Genetics
Trinity College Dublin, Ireland
In the review article, Dr Ongaro and Prof. Emilia Huerta-Sanchez outline evidence suggesting that several Denisovan populations, who likely had an extensive geographical range from Siberia to Southeast Asia and from Oceania to South America, were adapted to distinct environments.
They further outline a number of genes of Denisovan origin that gave modern day humans advantages in their different environments.
Among these is a genetic locus that confers a tolerance to hypoxia, or low oxygen conditions, which makes a lot of sense as it is seen in Tibetan populations; multiple genes that confer heightened immunity; and one that impacts lipid metabolism, providing heat when stimulated by cold, which confers an advantage to Inuit populations in the Arctic.
There are numerous future directions for research that will help us tell a more complete story of how the Denisovans impacted modern day humans, including more detailed genetic analyses in understudied populations, which could reveal currently hidden traces of Denisovan ancestry. Additionally, integrating more genetic data with archaeological information – if we can find more Denisovan fossils – would certainly fill in a few more gaps.
Dr Linda Ongaro.
The research was supported by the European Research Council.
Publication:Ongaro, L., Huerta-Sanchez, E. A history of multiple Denisovan introgression events in modern humans. Nat Genet (2024). https://doi.org/10.1038/s41588-024-01960-y
AbstractGiven the vast distanced over which Denisovans and their H. erectus ancestors had spread it is hardly surprising that a number of geographical varieties had begun to evolve and nor, given what we know of how archaic humans acted like ring species for some tens of thousands of years, that they, like Neanderthals, contributed some DNA to the emerging Eurasian H. sapiens.
The identification of a new hominin group in the Altai mountains called Denisovans was one of the most exciting discoveries in human evolution in the last decade. Unlike Neanderthal remains, the Denisovan fossil record consists of only a finger bone, jawbone, teeth and skull fragments. Leveraging the surviving Denisovan segments in modern human genomes has uncovered evidence of at least three introgression events from distinct Denisovan populations into modern humans in the past. Each of them presents different levels of relatedness to the sequenced Altai Denisovan, indicating a complex relationship between these sister lineages. Here we review the evidence suggesting that several Denisovan populations, who likely had an extensive geographical range, were adapted to distinct environments and introgressed into modern humans multiple times. We further discuss how archaic variants have been affected by demographic history, negative and positive selection and close by proposing possible new lines of future research.
Ongaro, L., Huerta-Sanchez, E.
A history of multiple Denisovan introgression events in modern humans.
Nat Genet (2024). https://doi.org/10.1038/s41588-024-01960-y
© 2024 Springer Nature Ltd.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.
How different the truth us turning out to be compared to the childish fairy tales, creationist's favourite myth-makers made up about 3,500 years ago, when they had only recently emerged from the Stone Age and knew nothing of the rest of the world outside their small area of the Middle East!
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