Evolutionary Impact of Social Isolation

One of the greatest mysteries in human evolution is how the Neanderthals went into extinction ~40 thousand years ago. This paper discusses the genome of a Neanderthal called “Thorin,” found in Grotte Mandrin in Mediterranean France. Thorin’s remains include a mandible and 31 teeth from between 52,900 and 48,050 years ago. These remains are linked to the PNII lithic industry, one of the final Neanderthal cultural phases in the region. Genomic analysis shows that Thorin belonged to a previously unknown Neanderthal lineage that diverged from other late European Neanderthals around 100,000 years ago and then remained genetically isolated for about 50,000 years. This isolation is unusual because other late Neanderthals were thought to be part of a single connected population.

Genetic analysis supports the isolation of this Neanderthal lineage. Thorin’s genome showed no signs of gene flow with other Neanderthals, including those living nearby. His mitochondrial DNA was most closely related to individuals from Gibraltar and Poland, and his Y chromosome also diverged early. Thorin also had high levels of homozygosity, with around 7% of his genome in long homozygous stretches, indicating recent inbreeding and a small group size. These findings suggest that his population had limited social contact with other Neanderthals. Interestingly, this isolated group also had a distinctive cultural identity, with stone tools that differed from the better-known Mousterian and Châtelperronian traditions in nearby areas.

The researchers conclude that Thorin's population likely represents one of the last Neanderthal groups in Europe, living in isolation until around 42,000 years ago. Their genetic and cultural separation may have made them more vulnerable to extinction. Unlike modern humans, who built wide social networks and exchanged genes across regions, these Neanderthal groups were fragmented and possibly avoided interbreeding—even with other Neanderthals. This paper adds more knowledge to the debate about Neanderthal extinction, suggesting that social and genetic isolation may have been just as important as external factors like climate or modern human expansion.

This is the paper I read: https://www.cell.com/cell-genomics/fulltext/S2666-979X(24)00177-0