How a 110,000-Year-Old Neanderthal Population Bottleneck May Hold the Key to Their Extinction

The story of the Neanderthals took a surprising turn in recent research. It turns out they may have faced extinction much earlier than scientists had believed.

A study, published in the journal Nature Communications, found that about 110,000 years ago, Neanderthals went through a “population bottleneck.” This event drastically reduced their genetic diversity.

So, what is a population bottleneck? It’s when a group of organisms experiences a sudden decline in genetic variety. This can happen for several reasons, like climate changes, hunting pressures, or disease outbreaks. The aftermath often leaves a population weak and struggling to survive.

To uncover this aspect of Neanderthal history, scientists examined the inner ear bones of Neanderthal skulls. They noticed a significant decrease in variation among these inner ear structures at the start of the Late Pleistocene period. This indicated a pivotal shift in the Neanderthal skeleton.

Typically, researchers rely on ancient DNA samples to learn about population changes. In this case, however, they used the ear bones as a clue. The semicircular canals, which help with balance and head movement, were specifically studied. These structures are established at birth and show “neutral” evolution, meaning they don’t influence survival. Tracking their changes can reveal insights about the population size and health.

The research team analyzed CT scans of inner ear bones from 30 Neanderthal specimens spanning three different time periods. They looked at 13 fossils from Sima de los Huesos in Spain, dating back 430,000 years, 10 from Krapina in Croatia, dated to around 120,000 years ago, and seven late Neanderthals from France and Belgium, dated between 64,000 and 40,000 years ago.

The findings showed that the later Neanderthals had a notable drop in variation compared to earlier groups. This evidence strongly indicates that a genetic bottleneck occurred more recently than previously thought.

The co-author of the study, Mercedes Conde-Valverde from the University of Alcalá, highlighted how this research paints a clearer picture of Neanderthal evolution. She noted that the sharp decline in diversity between the early and late Neanderthals provides robust evidence of the bottleneck event.

This research aligns well with past studies linking population shifts to declines in Neanderthal numbers, particularly in Europe. However, the situation for Neanderthals in southwestern Asia is still uncertain. More research is needed to confirm if similar patterns apply to those populations.