Neanderthal ears reveal the secrets of an ancient tragedy: what researchers have discovered.

Although Neanderthals are one of the most studied species of ancient humans, they still hold many secrets. For instance, researchers are intrigued by the question of why they went extinct, and a new study may shed light on this issue.

The work, published in the journal Nature Communications, explores in detail the "bottleneck" hypothesis. This refers to a reduction in genetic diversity that ultimately led to their extinction.

The authors analyzed remains from three excavation sites and conducted simulations of the structure of the semicircular canals in the inner ear—a bony structure that allows us to maintain balance. This structure was chosen because it is not heavily influenced by natural selection, making it a good indicator for tracking genetic changes in a population.

For comparison, the following remains were examined:

• remains from Sima de los Huesos, Spain (about 430,000 years ago) — these are not considered "true" Neanderthals, but rather early ancestors;
• remains from Krapina, Croatia (about 130-120,000 years ago);
• late Neanderthals from other parts of Europe (64-40,000 years ago).

The comparison of the shapes of the inner ear canals showed that Neanderthals experienced a significant decline in diversity at a late stage of their existence, which was not observed prior to that.

The researchers conclude that the "bottleneck" occurred sometime after 120,000 years ago.

The cause may be a sharp population decline, possibly linked to climate changes and the need for a substantial lifestyle overhaul. Notably, around this period, the Eemian interglacial occurred, characterized by a significant rise in temperatures, glacial melting, and the spread of forests. The expansion of forests could have displaced their usual prey (large herbivores) from their natural habitats, thereby reducing food availability.

However, other factors such as the spread of diseases, genetic isolation, and widespread inbreeding cannot be ruled out either.

The new study indicates that by the time our ancestors arrived in Europe, Neanderthal populations were already "not in the best shape." Yet, even this did not prevent them from surviving for tens of thousands of years before being ultimately replaced by Homo Sapiens around 40,000 years ago.

As previously reported, scientists found in 2024 that our ancestors interbred with Neanderthals for several thousand years. This occurred around 47,000 years ago.