Using bone fragments, some no bigger than a finger, California State University, Northridge anthropologist Hélène Rougier and an interdisciplinary team of international researchers have discovered that the last Neanderthals in Europe all descended from one lineage.
Incorporating new DNA data and archaeological evidence, their research indicates that the last European Neanderthals experienced a massive drop in their numbers following a significant climate incident — the onset of a major ice age. Those that survived ended up sharing the same gene pool in the years prior to their extinction some 40,000 years ago.
“This study clearly shows genetically that we have Neanderthals belonging to multiple lineages before the climate deterioration that started about 75,000 years ago,” Rougier said. “Combining the genetic data with the archaeological data, we were able to see a contraction in the distribution of Neanderthal sites that corresponded to a dramatic change in the climate, an ice age. The data shows that some of the Neanderthals found refuge in southwestern Europe, taking shelter in the valleys of southwestern France, while dying out in the rest of the continent.
“Then, we were able to track the Neanderthals as they expanded back across Europe following the ice age,” she continued. “But what was so interesting is that these Late Neanderthals were not very diverse anymore. They all shared the same genetic lineage.”
Rougier and her colleagues launched the study, “Archaeogenetic insights into the demographic history of Late Neanderthals,” which recently appeared in the journal PNAS, in hopes of understanding the demographic history of Neanderthals in Europe over the past 120,000 years.
They were surprised to discover nearly all Late Neanderthal individuals across Europe belonged to a single lineage of mitochondrial DNA — a smaller subset of genetic material passed down from mothers to their offspring. Their analysis dates this migration across Europe to some 60,000 years ago and suggests that it likely originated from a group that sought refuge from an ice age that gripped the continent between 75,000 and 65,000 years ago.
Once the ice retreated, the Neanderthals, who now all shared the same genetic ancestors, spread out again across Europe, from Spain to the Caucasus. Then, between 45,000 to 42,000 years ago, the Neanderthal population suddenly suffered a steep decline.
“It was like they went off a cliff,” Rougier said. “The population just collapsed. In about 2,000 years they were gone”
Rougier noted that 2,000 years is not a big window of time to facilitate the complete extinction of a species, particularly one that had survived for tens of thousands of years and through dramatic climate events like ice ages.
“The collapse corresponds to the time that we have early Homo sapiens starting to arrive in the territory,” she said. “Maybe our arrival added some competition for resources that was too much. Maybe they were more vulnerable because of the lack of diversity in their genetics. Or maybe some of the groups were competing against each other — in a prior study we did find evidence of cannibalism — and they wiped each other out.
“We don’t have the answers yet but, piece by piece, we are slowly putting together the picture of what life for humans—Neanderthals were a species of humans—was like tens of thousands of years ago,” Rougier said.