Neanderthals might have been on the path to extinction much earlier than experts previously believed, according to groundbreaking research published in Nature Communications on February 20. The study uncovers a critical "population bottleneck" event around 110,000 years ago, which drastically reduced genetic diversity among our closest human relatives. This revelation challenges prior assumptions, suggesting the Neanderthals' decline began long before their eventual disappearance.
Researchers focused on the inner ear bones of Neanderthals to identify this genetic bottleneck. The study analyzed the semicircular canals from 30 Neanderthals across three distinct time periods: 430,000 years ago, 120,000 years ago, and between 64,000 to 40,000 years ago. These Neanderthal samples originated from Sima de los Huesos in Spain, Krapina in Croatia, as well as various sites in France, Belgium, and Israel.
The findings reveal a significant reduction in the variation of inner ear bones among late Neanderthals compared to earlier groups. According to Mercedes Conde-Valverde, the reduction "is especially striking and clear, providing strong evidence of a bottleneck event." This bottleneck occurred more recently than 120,000 years ago and is indicative of substantial genetic loss.
To conduct their analysis, researchers employed CT scans to examine the Neanderthals' semicircular canals. This method allowed for precise observation of the inner ear structures, offering insights into the genetic diversity—or lack thereof—within these ancient populations.
Kristina Killgrove, the study's lead author and a staff writer at Live Science with a specialization in archaeology and paleoanthropology news, spearheaded the research. Killgrove is recognized for her contributions to science writing, having received awards from the Society for American Archaeology and the American Anthropological Association.
The study's findings align with previous research indicating population turnover that adversely impacted European Neanderthal numbers. However, it remains uncertain if this pattern extends to southwestern Asian Neanderthals, including those from Shanidar in Iraqi Kurdistan, as their skulls were not available for analysis.
