The discovery of the Denisovans was particularly spectacular, even by the standards of archaeology: Genetic analysis of a single finger bone fragment found in a single Siberian cave led to the revelation in 2010 that it was an unknown human species.
That revelation sparked an explosion of scientific investigation into the unexpected species. In time, more teeth surfaced in that same Denisova Cave in Siberia, after which the species is named. But bone-wise, that was that. No more Denisovan remains were found, to the general frustration of scientists everywhere – until a jawbone surfacing in Tibet was identified with the mysterious hominin in 2018 (not all agree on the identification), and that was that again.
Until this week, when a single child’s tooth found in Laos was announced to be Denisovan, generating enormous excitement in archaeological and anthropological circles.
The news, by Prof. Fabrice Demeter of the University of Copenhagen and an international team of researchers from Laos, Europe, the United States and Australia, appeared Tuesday in Nature Communications. The team is confident of their identification, on several grounds.
For one thing it is morphologically like the jawbone from Tibet, which indicates that they belong to the same taxon, the team says. Therefore, the Tam Ngu Hao 2 specimen most likely represents a Denisovan. Also, paleoproteomic analysis shows it to be Denisovan, and in addition, Denisovan DNA has been found in the cave sediment, Demeter tells Haaretz.
The Laotian tooth therefore supports a bevy of genetic evidence suggesting that the Denisovans had been extremely successful as human species go. It shows they had ranged from Siberia in the west, if not further, to the farthest corners of Southeast Asia, possibly even surviving until 15,000 years ago. This tiny, underdeveloped tooth enormously expands the more-or-less proven range of Denisovans, in keeping with recent genetic insights.
By the way, the Tam Ngu Hao cave is quite high in the mountains but the Laotian climate is categorically different from that of Siberia and was back then too.
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“This fossil represents the first discovery of Denisovans in Southeast Asia and shows that Denisovans were in the south at least as far as Laos. This is in agreement with the genetic evidence found in modern-day Southeast Asian populations,” Demeter said.
Living on and on
How many species of human there were, we do not know. Nor is there any particular reason to think any but us survive, despite the recent speculation that isolated Homo floresiensises (aka "hobbits") are still lurking in the nooks and crannies of Indonesia. Maybe they are, probably they’re not.
Who were the Denisovans? What did they look like? Genetic evidence shows them to be a sister species of Neanderthals, with the latter occupying Europe and the Denisovans living in Asia, to oversimplify the case massively. Their territories definitely overlapped. A teenage girl who lived (or died, rather) in that same Denisova Cave 90,000 years ago turned out to have a Neanderthal mother and Denisovan dad. She was a first-generation hybrid.
Later archaeologists analysing the sediment in the cave worked out when Denisovans lived in it, when Neanderthals lived in it and when Homo sapiens lived in it – yes, over 250,000 years, all three species spent time in Denisova Cave. Nice place, it was.
So what do we have in terms of solid Denisovan evidence? One finger bone and some teeth from Denisova Cave, the jawbone found high on the Tibetan plateau found by a monk, appropriately seeking enlightenment, and now this tooth, which was also discovered accidentally, and that’s it.
Why such paucity? Actually, for all the press about other human species, organic physical evidence (bones) remains incredibly elusive, and the environmental conditions in the Denisovan range are largely not conducive to preservation. And let us be clear that there are remains about which doubt remains – such the recently announced “new species” Homo longi or Dragon Man, reported in China, which some think is an early Neanderthal despite being so far east. Some suggest it was a Denisovan.
Even when one finally finds a fossil of a human, genetic analysis is not always possible. In fact, there are a few Middle to Late Pleistocene fossils in Asia that don’t seem to be Homo erectus, who did prowl those parts in the day; they’re not sapiens; and some suggest they are in fact Denisovan. The jury is still out and arguing.
As for the tooth, it was chanced upon during an archaeological survey in a cave named Tam Ngu Hao 2, aka Cobra, in a remote area of Laos in 2018, the team explains. It dates to about 164,000 to 131,000 years ago and was found with a host of other animal teeth. And, the team surmise, it belonged to a girl. A little one.
Little girls’ teeth look like little boys’ teeth, but the team didn’t detect male-specific proteins, which isn’t conclusive but it is indicative, they explain. The team hopes to pursue genetic analysis of the tooth at GeoGenetics in Copenhagen, Demeter says.
While the fate of the hobbits is now being revisited by the popular press, that of the Denisovans is clearer – they’re gone. But our ancestors mixed not only with Neanderthals and some weird “ghost hominins” (ancient, unidentified ones) but with the Denisovans too.
While Neanderthal genes are just about everywhere, even in sub-Saharan Africans to a low degree, Denisovan genes have been found mainly in today’s Modern Papuans, indigenous Australians, Oceanic and Melanesian peoples, and also, though to a much lesser extent, mainland Southeast Asian peoples. Genes from Denisovans are believed to enable Tibetans to thrive at high altitudes, but the highest concentration by a long way has been found in an indigenous group in the Philippines: the Ayta Negritos.
After all this – could it be that the tooth belonged not to a Denisovan but to a Neanderthal? Theoretically, but if so it would be the most southeastern Neanderthal ever found by a vast distance. Also, the tentative identification of it as Denisovan explains the genetic data about their mark on southeastern populations.
It would also support the theory that this enigmatic species was hardy: living in Siberia (albeit a nice part of it), on the low-oxygen environment of the Tibetan plateau and now in steamy Southeast Asia, which, based on other teeth found in the same cave as the girl, featured elephants, deers, pigs and rhinos, and presumably tasty giant herbivores. It would show these people had a high degree of plasticity to adapt to very diverse environments, the team says.
Associate Prof. Mike Morley from the Microarchaeology Laboratory at Flinders University, Adelaide, does not hedge his bet: “We have essentially found the ’smoking gun’ – this Denisovan tooth shows they were once present this far south in the karst landscapes of Laos,” he states.
So why did they die out? Um, did we do it? We do not know and can’t even reasonably speculate since we can hardly find any of their remains.