Unraveling Neanderthal Decline: Insights from Genetic Clues

Neanderthal DNA analysis has significantly advanced our understanding of the challenging eras leading to the extinction of these ancient humans.

As climate cooled, Neanderthal populations diminished, ultimately restricting them to southwestern France. With a subsequent warming trend, these ancient humans began to expand their range. However, due to a drastic reduction in genetic diversity, even widespread populations exhibited similar DNA profiles.

This scenario—a small, isolated population with limited genetic variability—likely contributed to their extinction.

Having inhabited Europe and Asia for hundreds of thousands of years, Neanderthals vanished from the archaeological record around 40,000 years ago. Previous DNA studies indicate significant genetic changes occurred as their populations dwindled, especially among late Neanderthals from approximately 60,000 years ago, who displayed genetic similarities distinct from their earlier counterparts. “There must have been some population turnover towards the end of Neanderthal history,” states Cosimo Posth from the University of Tübingen, Germany.

To examine these changes, Posth and his team sequenced DNA from 10 Neanderthals across six locations in Belgium, France, Germany, and Serbia. They focused on the mitochondrial DNA inherited from mothers and compared it to 49 previously sequenced genomes.

The findings revealed that nearly all Neanderthals who lived between 60,000 and 40,000 years ago belonged to a single lineage that emerged around 65,000 years ago, with no traces of older lineages. “This strongly indicates that a population turnover occurred,” affirms Posth.

Additionally, the research team analyzed a database of Neanderthal remains, noting a significant geographic contraction in population density towards southwestern Europe from 80,000 to 70,000 years ago, especially concentrated in southwestern France. “This was likely triggered by climate change,” explains Posth. “Around 75,000 years ago, a major ice age commenced, prompting the Neanderthals to retreat further into southwestern Europe.”

The emerging lineage likely originated in southwestern France, expanding after the warming climate of over 60,000 years ago. However, despite this geographic expansion, the overall population size did not significantly increase.

One remarkable exception is an individual named Thorin, discovered in Mandolin Cave, France. At approximately 50,000 years old, Thorin’s DNA indicates strong ties to more ancient lineages, revealing that some genetic lines likely survived the previous population decline. Posth notes that Thorin is “the only one who doesn’t fit into the established narrative.”

The ability to trace Neanderthal migrations enriches our understanding of their history, according to Tarshika Vimala, who researched Thorin at the University of California, Berkeley.

Vimala also highlighted previous findings that confirmed fluctuations in Neanderthal populations, leading to the loss of specific lineages. A 2021 study suggested that population replacement occurred roughly 100,000 years ago, possibly as a response to climate changes.

Neanderthals’ pattern of living in small, isolated bands may have heightened their extinction risk. Vimala estimates their group sizes ranged between 3 and 60 individuals. Prof. Poss remarked that this could have allowed harmful genetic variations to develop, increasing the vulnerability of each population to random events.

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