Uncovering the Shocking Truth: What Caused the Neanderthal Population Crash 110,000 Years Ago?

The Neanderthal population flourished in Eurasia for more than 250,000 years. However, around 110,000 years ago, they faced a significant challenge known as a genetic bottleneck. This bottleneck led to a sharp decline in their numbers and a loss of diversity in their physical and genetic traits.

Even though Neanderthals went extinct about 40,000 years ago, this earlier population decline indicates they were already having a tough time long before their final disappearance.

Scientists have been studying both fossil records and DNA evidence to understand how this sharp decline transformed Neanderthal evolution on Earth.

For a long time, researchers believed that Neanderthals had a fairly stable evolution. Recent findings suggest that their history was much more variable and complex. Fossils show that early Neanderthals had a wide range of genetic and physical diversity, which helped them adapt to various environments across Europe and Asia.

However, about 110,000 years ago, their diversity fell dramatically. This decline signifies a significant loss of individuals and possibly entire groups.

Interestingly, between 430,000 and 120,000 years ago, Neanderthal diversity actually increased before the drastic drop. This earlier increase might have affected their ability to cope with later environmental challenges.

To investigate this decline further, researchers examined the bony labyrinth—part of the inner ear related to balance—in Neanderthal fossils. This analysis provided insights into genetic variation when DNA could not be studied due to degradation.

Results showed that older Neanderthals, like those from Krapina, Croatia, had much greater variation in their inner ear structures than later Neanderthals. This finding supports the idea that a bottleneck event seriously impacted their population. It also suggests that Neanderthals did not start with low genetic diversity as once thought.

Fossils from Sima de los Huesos, Spain, which date back 430,000 years, indicate their pre-Neanderthal ancestors were as diverse as early Neanderthals, further suggesting that Neanderthals began as a genetically rich species.

So, what caused this population collapse? The exact reasons remain unclear, but several theories exist. One possibility is climate change, where severe cold periods limited food supplies, leading to a population decline.

Another theory involves competition with other hominins, especially the Denisovans, who shared their habitats. During this time, while Homo sapiens were not yet prevalent in Eurasia, interactions with other hominins may have added to resource pressures.

Some experts believe that disease outbreaks could have significantly impacted Neanderthal groups. An epidemic might have struck, decimating isolated populations and leaving only a small number of survivors.

Additionally, this research challenges earlier beliefs that Neanderthals faced an initial genetic bottleneck at the start of their lineage. The shape of fossils indicates that early Neanderthals had as much diversity as their pre-Neanderthal ancestors, suggesting they were originally a more varied species than previously understood.