Unlocking Neanderthal Secrets: How Their Inner Ears Uncover a Catastrophic Event in Human Evolution

Neanderthals appeared around 250,000 years ago, evolving from earlier European populations. They adapted to some tough conditions in Eurasia, and scientists are now discovering how their genetic diversity changed over time.

Recent research led by Alessandro Urciuoli from the Catalan Institute of Paleontology suggests that Neanderthals went through a significant population bottleneck rather than facing gradual decreases in diversity. This challenges the common belief that they experienced a drop in genetic variety from the moment they diverged from their pre-Neanderthal ancestors.

Fossil evidence from Spain and Croatia shows that early Neanderthal groups had more physical variety than previously thought. Interestingly, classic Neanderthals displayed much less diversity in their features.

Why Study the Inner Ear?

Researchers examined the semicircular canals in the inner ear, which help with balance. By studying these structures, they learned more about the population’s genetic diversity. A more varied population tends to have different shapes in their inner ear canals.

The Bottleneck Revelation

Urciuoli explains that the sharp decline in diversity, especially seen between fossils from Krapina and classic Neanderthals, supports the idea of a bottleneck. The findings suggest that Neanderthals from the Sima de los Huesos exhibited similar diversity levels to earlier Neanderthals from Krapina.

An important point is that this decline didn’t happen when Neanderthals first emerged but occurred later, affecting their classic form.

Challenging Old Myths

Previous beliefs suggested Neanderthals followed a single evolutionary path, but ancient DNA reveals that multiple migrations and smaller groups existed. The idea of a swift decline in diversity has been contested, with new insights showing that classic Neanderthals suffered significant loss of variability only later.

What’s Next?

This bottleneck aligns with severe climate changes in Eurasia. Researchers believe that Neanderthals’ morphological variety diminished due to new migrations or local extinctions. This suggests a single genetic squeeze might have shaped the classic Neanderthal appearance.

The study of fossils and genetics together offers a clearer picture of how populations developed. Different groups, separated by geography, could have intermixed or disappeared, leading to a complex web of Neanderthal diversity. The ongoing research includes analyzing petrosal bone structure and ancient proteins to shed more light on these ancient humans.

Understanding the details of Neanderthal evolution is crucial as it alters our views on when and how human ancestors diverged. If Neanderthals maintained high diversity longer than expected, this indicates a more complex evolutionary timeline. It reinforces the importance of regional populations, which could have evolved differently.

Insights from Neanderthal inner ear shapes hint at past population dynamics. By investigating the structures that don’t directly impact survival, scientists can uncover trends in ancient populations. This area of research continues to redefine how we perceive human ancestry, highlighting migrations, interactions, and gradual changes rather than abrupt separations.

For further details, the study is published in Nature Communications.

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