Uncovering the Unexpected Reasons for the Neanderthal Population Decline 110,000 Years Ago

The Neanderthal population was a group of humans that lived in Europe and parts of Asia for more than 250,000 years. However, about 110,000 years ago, they went through a significant decline in their genetic diversity. This event, known as a genetic bottleneck, resulted in a substantial reduction in their population size, leading to less variety in their traits and characteristics.

While Neanderthals are known to have become extinct roughly 40,000 years ago, this earlier population decline indicates that they were already facing serious survival challenges long before their eventual disappearance. Recent studies, which examined both fossil remains and DNA data, suggest that this decrease in population had a profound effect on how Neanderthals evolved over time.

For a long time, scientists thought that Neanderthals evolved gradually and maintained stable populations. However, new research presents a different picture, showing that their history was much more complex and unstable. Fossil evidence from earlier periods indicates that early Neanderthals were genetically diverse and physically varied, which likely helped them adapt to different environments across Europe and Asia.

Around 110,000 years ago, something catastrophic happened. The genetic diversity that characterized Neanderthals sharply declined, indicating that many individuals or even entire groups were lost. Curiously, fossil records show that Neanderthal diversity had actually increased from around 430,000 to 120,000 years ago before this sharp decline took place. This earlier increase in diversity might have been beneficial, but the later collapse may have made it harder for them to cope with environmental changes in the long run.

To investigate the reasons behind this population decline, researchers analyzed a part of the inner ear in Neanderthal fossils. This part, called the bony labyrinth, helps with balance and movement. It also offers a unique way to study genetic variation, especially when DNA is too damaged to analyze. The results revealed that earlier Neanderthals exhibited a lot of variation in their inner ear structures compared to later examples known as “classic” Neanderthals. This supports the idea that a genetic bottleneck had a serious impact on their population.

Interestingly, these findings suggest that Neanderthals did not start off with low genetic diversity. Fossils from Sima de los Huesos in Spain, which are about 430,000 years old and represent their pre-Neanderthal ancestors, showed as much diversity as early Neanderthals. This indicates that Neanderthals were initially a diverse species but lost much of that genetic variation over time.

The reasons behind this genetic bottleneck are still uncertain, but several possibilities have been proposed. One theory suggests that climate change during periods of extreme cold may have led to a severe reduction in available food, pushing Neanderthal populations into decline. Another possibility is that competition with other hominins, like the Denisovans, who shared the same territories, may have exerted pressure on resources.

In addition, some researchers point to the impact of diseases, which could have swept through isolated Neanderthal groups, leading to significant population losses. Lastly, new evidence challenges the idea that Neanderthals went through an earlier genetic bottleneck at the beginning of their lineage, as the fossil morphology shows that early Neanderthals had as much diversity as their pre-Neanderthal ancestors, indicating they started with a richer genetic variation than previously thought.