Video: Neanderthals and Denisovans – Not just savage brutes after all
The year was 1856, miners uncovered some bones in the Neander Valley in Germany. A local schoolteacher recognized these bones as distinct from modern human bones. He gave them to anthropologist Herman Schaaffhausen, who suggested that they belonged to an ancient human. Schaafhausen concluded that these humans were savage cave-dwellers. They were named Homo neanderthalensis or Neanderthals in 1864. Neanderthal remains had been found earlier in Belgium in 1830 and Gibraltar in 1848 but they were not recognised as such at that time.
Fast forward to the 20th century and numerous other Neanderthal discoveries were made. They became a legitimate species of ancient humans, although they were still considered an evolutionary dead-end, very distinct from humans.
Since then, we have been curious to find out who exactly they were and how they were related to us. Early 20th century scientists even theorised that they had interbred with early modern humans. In 2010, when geneticists mapped Neanderthal genome, they found that they HAD interbred with humans, probably when the latter ventured into Neanderthal territory.
Who were the Neanderthals?
They are our closest extinct relatives with whom we share a common ancestor, separating around 500,000 to 650,000 years ago. We know more about them than any other extinct human species. They lived from around 400,000 till about 40,000 years ago (although they could have been around from as early as 800,000), across Southwest and Central Asia and Europe. While we were evolving in Africa, Neanderthals were doing so in Europe and Asia. We also know that they lived alongside early modern humans for a part of their existence. Our encounters with these cousins of ours were not always violent. Clearly there was romance in the air too because early modern humans and Neanderthals also interbred. As a result, most of us outside Africa have inherited 1.5 to 2% of their DNA. This DNA may have helped those early humans to adapt to their new environments when they left Africa around 60,000 years ago. We may have got thicker hair and skin from them, helping us to cope with cold European and central Asian winters. Our immune system may also have benefited due to this interbreeding.
The strong, muscular Neanderthals had a prominent brow ridge, a very big, wide nose, large front teeth and a very very small chin. They ate large mammals but also plants, fungi mussels, seals. While they had had a reputation of being savage brutes, our understanding of their intelligence has changed with more discoveries. We now know that they were skilled toolmakers, who made spears and axes. Plus, 300,000 years ago they developed an innovative stone technology known as the Levallois technique, which required making pre-shaped stone cores that could finished into a tool at a later time. They were intelligent hunters, who were able to communicate with each other. There is also evidence that they looked after their sick and buried their dead, indicating a social structure based on fellow-feeling.
Some jewellery made from eagle talons has been discovered, from as far back as 130,000 years ago; as well as pierced animal teeth and ivory objects. It is also suggested that they used pigment to decorate their bodies. In 2018, artwork was found in three different caves in Spain, older than 64,000 years ago and this is thought to be made by Neanderthals because there is no evidence of human presence in this area at that time. Not savage brutes after all!
Then 40,000 years ago they disappeared, coinciding with human arrival into Europe. Their numbers had already started declining before humans arrived, as is evident from the genome of one female from the Altai Mountains in Siberia that shows long term inbreeding. Perhaps a harsh and fluctuating climate and competition from modern humans led to their demise.
Who were the Denisovans?
Further excitement occured with the discovery of a finger bone of another extinct species in Denisova Cave in the Altai Mountains in Siberia, in 2010. These Denisova hominins are now popularly known as Denisovans. A lineage that developed into Neanderthals and Denisovans is estimated to have separated from the lineage of modern humans around 500,000 to 750,000 years ago.
In the last decade or so, there have been unprecedented advances in DNA extraction and analysis techniques. And we have found that Homo sapiens not only interbred with Neanderthals but also with Denisovans, and modern non-African populations carry small amounts of DNA from both. Furthermore, Neanderthals and Denisovans also interbred with each other, as was evident from the DNA of Denny, a 13-year-old girl with both Neanderthal and Denisovan parents.
Denisovan genome suggests that they shared a common ancestor with Neanderthals but while the latter remained primarily in the cold Eurasian habitat, Denisovans were more mobile, ranging from Siberia to Southeast Asia.
While the genome of all non-African modern humans contains portions of Neanderthal DNA ranging from 1.5 to 2 %, Denisovans seem to have contributed a higher share, with about 3% to 5% of the DNA of Melanesians and Aboriginal Australians, and around 6% in Papuans deriving from them. Other modern East Asian populations also have a smaller percentage of Denisovan DNA.
An analysis from 2019 suggests that there may have been three distinct species of Denisovans that spread all over Eurasia – from Siberia to Indonesia – and that our ancestors interbred with all three. Modern Papuans carry hundreds of gene variants from two deeply divergent Denisovan lineages that separated over 350,000 years ago. One of these may have also interbred with Homo sapiens east of the Wallace line in the Pacific, probably as early as 15,000 years ago, while a third lineage occurs in modern East Asians.
Denisovan DNA recovered from Baishiya Karst Cave in Tibet was analysed in October 2020 to be around 100,000 to 60,000 years old but possibly as recent as 45,000 year old. The cave is over 3,000 meters above sea level, which means Denisovans may have adapted to high altitudes, and they may have passed this adaptation on to modern Tibetans.
So, we not only lived side-by-side with both Neanderthals and Denisovans, we also mated with them. They contributed to our existing gene-pool and to our evolution. They left their DNA in us.
One more thing that I did not mention in the video: Neanderthal DNA can also be found in people of African descent, whose ancestors got the DNA due to back migrations into Africa, from Europe and Asia.
Clearly, we have never been pure humans, much less pure races. Can you imagine what else we will find as more remains are discovered, and more DNA is analysed? I for one cannot wait!
Title music: Hovering Thoughts by Spence (YouTube Music Archive)
All images: Public Domain/ Wikimedia
Main Image: Reconstruction of Neanderthal woman (2004) Cro-Magnons Conquered Europe, but Left Neanderthals Alone. PLoS Biol 2(12) e449. httpsdoi.org10.1371journal.pbio.0020449
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