The jawbone of a Neanderthal known as Thorin, thought to have belonged to an isolated group
Xavier Mus
Genetic analysis of Neanderthal fossils found in France has revealed that they are the remnants of a previously unknown lineage of ancient people that remained extremely isolated for more than 50,000 years, shedding new light on the final stages of the species’ existence.
The fossil has been named Thorin, after a character from J.R.R. Tolkien’s novels. The Hobbitwas discovered in the Mandrine Cave in the Rhône Valley in southern France in 2015, when Ludovic Slimac of the Toulouse Center for Human Biology and Genomics found a tooth in the cave soil. After nine years of painstaking excavation, researchers uncovered 31 teeth, a jawbone, partial skull, and thousands of other bone fragments.
The discovery of so many fossils of Neanderthals, who lived in Eurasia from about 400,000 to 40,000 years ago and are now extinct, is extremely rare and a surprising find in itself.
Even more surprising, even though DNA doesn’t normally preserve in warm climates, a fragment of Thorin’s tooth yielded his genome, revealing that the fossil was male but solving a mystery that will take years to unravel.
Srimak and his colleagues compared Thorin’s genome with those of other Neanderthals and estimated that he lived about 105,000 years ago, but archaeological evidence and isotope analysis of his bones clearly show that Thorin lived no more than 50,000 years ago, making him a “late Neanderthal” from the final stage of Neanderthal existence.
“We (geneticists) were convinced for a long time that Thorin was indeed an early Neanderthal because his genetic lineage is very distantly related to modern Neanderthals from the same region,” says team member Tarshika Vimala of the University of Copenhagen, “while archaeologists were convinced that Thorin was a late Neanderthal. It took years of work on both sides to arrive at that answer.”
Eventually, the researchers realized they must have discovered a previously unknown Neanderthal lineage: Thorin was part of a small group that lived between 42,000 and 50,000 years ago. This group was likely a remnant of a much older Neanderthal population that split off from the main Neanderthal population about 105,000 years ago and remained genetically isolated for more than 50,000 years afterwards.
Thorin’s bones unearthed in the Mandolin Cave in France
Ludovic Slimak
Thorin’s DNA showed no evidence of interbreeding between his lineage and the main Neanderthal population, despite their close proximity. “Thorin was completely different from other Neanderthals,” Slimak says.
This isolation may have made this population particularly vulnerable: “Prolonged isolation and inbreeding can reduce genetic diversity over time, which is detrimental to a population’s survival, which in turn can negatively affect its ability to adapt to a changing environment,” Vimala says.
Srimak, Vimala and their colleagues then reanalyzed the genome of another Neanderthal who lived about 43,000 years ago at Les Côtés in France, and found traces in its DNA of a “ghost population” that interbred with another, previously unknown, Neanderthal group about 15,000 to 20,000 years ago.
“This means that there weren’t just two populations among late Neanderthals, but possibly three,” says Slimak. Previously, it was thought that all Neanderthals before their extinction were part of a single genetically similar population.
“The evidence from Mandrin Cave is extremely exciting because it gives us fascinating insights into late Neanderthal populations and their trends,” says Emma Pomeroy from the University of Cambridge.
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