Around 65,000 years ago, Neanderthal populations in Europe underwent a catastrophic genetic bottleneck. A new study reveals that all but one Neanderthal lineage died out, leaving a single group to repopulate the continent. This event may provide critical clues to understanding the ultimate extinction of Neanderthals, who vanished entirely roughly 40,000 years ago.
The Genetic Bottleneck
Researchers analyzed mitochondrial DNA (passed down maternally) from 10 Neanderthal fossils found in Belgium, France, Germany, and Serbia, combined with 49 previously sequenced samples. The analysis revealed a surprising shift: before 65,000 years ago, Europe hosted multiple distinct Neanderthal genetic lineages. After that date, only one lineage originating from southwestern France remained, spreading across the continent.
This isn’t just a population fluctuation; it’s a major disruption in Neanderthal history, as senior author Cosimo Posth of the University of Tübingen explains. The shift suggests a widespread collapse of existing Neanderthal groups.
Climate Change as a Catalyst
The timing coincides with the onset of a harsh glacial period, roughly 75,000 years ago. While Neanderthals had survived earlier ice ages, this one proved different. The researchers believe northern European Neanderthal groups perished, while the southwestern French population was already adapted enough to endure the extreme climate. This surviving group then expanded into the vacated territories.
The study’s findings indicate that the Late Neanderthals had severely reduced genetic diversity compared to their predecessors. The last groups were nearly identical on a genetic level across Europe, from Spain to the Caucasus.
Reduced Diversity, Increased Vulnerability
Low genetic diversity is a red flag for any species. It reduces adaptability and increases susceptibility to disease, environmental changes, and inbreeding. Posth suggests this lack of variation likely contributed to the Neanderthals’ eventual extinction, though it wasn’t the sole factor.
Interestingly, despite the genetic impoverishment, Late Neanderthals displayed greater cultural and archaeological diversity across sites. This suggests that while genetically similar, these groups remained relatively isolated, developing unique tools and art styles.
A Pattern of Extinction and Recolonization
The study supports the idea that Neanderthal populations frequently replaced each other. Groups died out in certain regions, only to be recolonized by survivors from elsewhere.
The research highlights a crucial pattern: Neanderthals didn’t just vanish; they were repeatedly pushed to the brink, and in the final stages, lacked the genetic resilience to recover. Further research, using nuclear DNA instead of mitochondrial, could confirm these findings. However, nuclear DNA is far more degraded in ancient fossils, posing a significant analytical challenge.
The collapse of Neanderthal genetic diversity serves as a stark reminder of the precariousness of survival, even for species that once dominated entire continents.
