Until now, the main theories for the Neanderthals’ demise have been climate change, a disease epidemic, or even violence—or interbreeding—with Homo sapiens.
Neanderthals lived in Europe and Asia for a long time, including a period when they coexisted with early modern humans until their sudden extinction 40,000 years ago.
French archaeologist Ludovic Slimak said it was the last time more than one human species lived together on Earth. It was “an extremely mysterious moment, because we don’t know how an entire humanity from Spain to Siberia could suddenly disappear.”
Slimak is the lead author of a new study in the journal Cell Genomics that examined the fossilized remains of a Neanderthal discovered in France’s Rhone Valley in 2015.
The remains were found in the Mandrin cave, which is known to have hosted both Neanderthals and Homo Sapiens over time.
The Neanderthal, named Thorin after the dwarf in JRR Tolkien’s book “The Hobbit,” is a rare find.
Thorin is the first Neanderthal to be unearthed in France since 1978 and one of approximately 40 Neanderthals discovered across all of Eurasia.
ONLY 50 THOUSAND YEARS
Slimak said archaeologists had spent a decade in unsuccessful efforts to extract DNA from the Mandrin cave when they found Thorin.
“As soon as the body was exhumed,” he said, they sent a molar fragment to geneticists in Copenhagen for analysis.
When the results came back, the team was stunned. Archaeological data suggested the body was 40,000 to 45,000 years old, but genomic analysis revealed it was 105,000 years old.
“Someone on the team must have misunderstood,” Slimak said.
IT TOOK 7 YEARS TO FIX THE STORY
Analysis of isotopes from Thorin’s bones and teeth showed that he lived in an extremely cold climate, matching an ice age around 40,000 years ago when only Neanderthals lived.
But Thorin’s genome did not match that of any previously discovered European Neanderthals at the time. Instead, it was similar to the genome of Neanderthals from around 100,000 years ago, which had caused the confusion.
Thorin appeared to be a member of an isolated and previously unknown community descended from some of Europe’s earliest Neanderthal populations, the researchers said.
“The lineage leading to Thorin may have split from the lineage leading to other late Neanderthals around 105,000 years ago,” senior study author Martin Sikora of the University of Copenhagen said in a statement.
This other lineage then spent 50,000 years “without any genetic exchange with the classic European Neanderthals,” some of whom lived just two weeks’ walking distance away, Slimak said.
DANGERS OF CONSISTENT MARRIAGE
Such long-term social isolation would have been unthinkable for Homo sapiens, cousins of Neanderthals, especially since the Rhone Valley was a major migration corridor between Northern Europe and the Mediterranean at the time.
Archaeological finds have long suggested that Neanderthals lived in a small area, just a few dozen kilometers from their homes.
Homo sapiens, by contrast, had “infinitely large” social circles spanning tens of thousands of square kilometers, Slimak said.
Neanderthals are also known to have lived in small groups, so not having to travel far likely meant they didn’t have many mate options outside their own families.
This type of inbreeding reduces genetic diversity within a species, which can spell disaster in the long run.
Rather than killing off Neanderthals per se, their failure to interbreed may have made them more vulnerable to some of the other popular theories about their demise.
“When you’re isolated for a long time, you limit the genetic diversity you have, which means you’re less able to adapt to changing climates and pathogens. It also limits you socially because you’re not sharing knowledge or evolving as a population,” said population geneticist Tharsika Vimala of the University of Copenhagen.
