New study challenges the theory that Neanderthals originated after an evolutionary event that implied the loss of part of their genetic diversity.
Neanderthals first appeared around 250,000 years ago, evolving from earlier European populations known as “pre-Neanderthals,” which lived across Eurasia between 500,000 and 250,000 years ago. For a long time, researchers believed Neanderthals underwent little significant evolutionary change. However, recent paleogenetic studies analyzing DNA from fossils have revealed a major loss of genetic diversity between early Neanderthals (also called “ancient Neanderthals”) and their later counterparts, known as “classic Neanderthals.”
This genetic loss, known as a “bottleneck,” typically results from a sharp decline in population size. Paleogenetic evidence suggests that this event occurred around 110,000 years ago.
Scientists had also widely assumed that an earlier bottleneck occurred at the origin of the Neanderthal lineage. As a result, previous hypotheses were based on the idea that the first Neanderthals had lower genetic diversity than their pre-Neanderthal ancestors due to an earlier population decline.
However, the existence of a bottleneck at the origin of the Neanderthals has not been confirmed yet through paleogenetic data, mainly due to the lack of genetic sequences old enough to record the event and needed for ancient DNA studies.
New Insights from Inner Ear Morphology
In a study led by Alessandro Urciuoli (Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona) and Mercedes Conde-Valverde (Cátedra de Otoacústica Evolutiva de HM Hospitales y la Universidad de Alcalá), researchers measured the morphological diversity in the structure of the inner ear responsible for our sense of balance: the semicircular canals. It is widely accepted that results obtained from studying the morphological diversity of the semicircular canals are comparable to those obtained through DNA comparisons.
The study focused on two exceptional collections of fossil humans: one from the Sima de los Huesos site of Atapuerca (Burgos, Spain), dated to 430,000 years old, which constitutes the largest sample of pre-Neanderthals available in the fossil record; and another from the Croatian site of Krapina, this representing the most complete collection of early Neanderthals and dated to approximately 130.000-120.000 years ago.
The researchers calculated the amount of morphological diversity (i.e., disparity) of the semicircular canals of both samples, comparing them with each other and with a sample of classic Neanderthals of different ages and geographical origins.
Key Findings: Confirming and Challenging Previous Assumptions
The study’s findings reveal that the morphological diversity of the semicircular canals of classic Neanderthals is clearly lower than that of pre-Neanderthals and early Neanderthals, which aligns with previous paleogenetic results.
Mercedes Conde-Valverde, co-author of the study, emphasized the importance of the analyzed sample: “By including fossils from a wide geographical and temporal range, we were able to capture a comprehensive picture of Neanderthal evolution. The reduction in diversity observed between the Krapina sample and classic Neanderthals is especially striking and clear, providing strong evidence of a bottleneck event.”
On the other hand, the results challenge the previously accepted idea that the origin of Neanderthals was associated with a significant loss of genetic diversity, prompting the need to propose new explanations for their origin. “We were surprised to find that the pre-Neanderthals from the Sima de los Huesos exhibited a level of morphological diversity similar to that of the early Neanderthals from Krapina,” commented Alessandro Urciuoli, lead author of the study. “This challenges the common assumption of a bottleneck event at the origin of the Neanderthal lineage,” the researcher stated.
Reference: “Semicircular canals shed light on bottleneck events in the evolution of the Neanderthal clade” by Alessandro Urciuoli, Ignacio Martínez, Rolf Quam, Juan Luis Arsuaga, Brian A. Keeling, Julia Diez-Valero and Mercedes Conde-Valverde, 20 February 2025, Nature Communications.
DOI: 10.1038/s41467-025-56155-8
Funding: MCIN/AEI, Generalitat de Catalunya, NextGenerationEU
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.
2 Comments
Look…! Og have kool headband…!
That was an oddly semicircular narrative leaving me with the impression that a lot of work by dedicated researchers is ongoing in this field, a seeming process-oriented rather than goal-oriented endeavor. I dislike researchers being compelled to present some contrived narrative to justify the resources dedicated to these endeavors. I am encouraged that real and productive work is being done.