Neanderthal Genetic Bottleneck 110,000 Years Ago May Explain Their Decline

A significant decline in genetic diversity among Neanderthals around 110,000 years ago has been identified, potentially contributing to their eventual extinction. Research analysing the structure of their inner ear bones suggests that a population bottleneck, which drastically reduced their numbers, may have occurred. Such events, typically caused by climate shifts, disease, or external threats, can weaken a species by limiting genetic variation. The findings provide new insights into the challenges Neanderthals faced long before their disappearance from the fossil record.

Genetic Evidence of Declining Diversity

According to a study published in Nature Communications, researchers examined the inner ear structures of Neanderthal fossils to trace changes in genetic diversity. The semicircular canals, crucial for balance, were analysed through CT scans of 30 Neanderthal skulls spanning different time periods. A significant reduction in variation was observed in specimens dating to the Late Pleistocene, indicating a population decline that could have impacted their resilience.

Research Method and Key Observations

Fossil samples were collected from three distinct periods. Early Neanderthals from Spain's Sima de los Huesos, dated to 430,000 years ago, displayed greater diversity in inner ear structure. In contrast, Neanderthals from Krapina, Croatia, dating to 120,000 years ago, and later specimens from France, Belgium, and Israel, dating to 64,000–40,000 years ago, showed a marked reduction in variation. This shift, as noted in a statement by Mercedes Conde-Valverde, a biological anthropologist at the University of Alcalá in Spain, provides strong evidence of a genetic bottleneck.

Impact on Neanderthal Survival

The study's findings align with previous research suggesting population turnover among European Neanderthals. The extent to which similar trends occurred in southwestern Asia remains uncertain, as skulls from sites like Shanidar in Iraqi Kurdistan were not included in the analysis. Genetic decline may have left Neanderthals vulnerable to environmental pressures and competition, further accelerating their decline.