A study led by the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), conducted within the framework of the European Marie Skłodowska-Curie PUSHH network and supported by Fundación Atapuerca–Reale, has used proteins preserved in dental enamel to investigate the evolutionary history of cave bears. Published in Scientific Reports, the research presents the largest palaeoproteomic dataset ever assembled for this iconic lineage.

Unlike ancient DNA, which is rarely preserved beyond several hundred thousand years, proteins preserved in dental enamel can survive for much longer periods. Thanks to this exceptional preservation, the research team was able to recover molecular information from species that lived during the Early and Middle Pleistocene, a time interval that remains largely inaccessible to conventional genetic studies.

The research team analysed dental remains from 55 bears recovered from sites in Spain, Portugal and Italy, with particularly strong representation from the Sierra de Atapuerca (Burgos, Spain). Fossils from Gran Dolina, Sima de los Huesos and Cueva Fantasma provide the chronological backbone of the study, making it possible to trace the evolution of the cave bear lineage over nearly one million years.

One of the study's most significant findings concerns Ursus dolinensis, an extinct species described from fossils recovered from level TD4 at the Gran Dolina site, whose position within the bear evolutionary tree has been debated for decades. Proteomic analyses indicate that it occupied a basal position within this lineage, supporting the hypothesis that it represents an early form of the evolutionary branch that gave rise to Ursus deningeri and, ultimately, Ursus spelaeus, the classic cave bear.

A new research line at CENIEH
Thanks to palaeoproteomics—a discipline that makes it possible to recover molecular information from fossils too old to preserve ancient DNA—the researchers have been able to clarify key aspects of Pleistocene bear evolution. "Through the analysis of fossil proteins, we have been able to confirm the hypothesis that the bears recovered from Gran Dolina represent one of the earliest forms of the lineage that eventually gave rise to cave bears," explains Elena Santos, second author of the paper and a specialist in the study of this taxon.

This study reflects CENIEH's strategic commitment to palaeoproteomics, a research line that has been strengthened by the launch of the Centre's new Molecular Palaeobiology Laboratory in early 2026. Funded by the Spanish Ministry of Science, Innovation and Universities and the European Union–NextGenerationEU through Spain's Recovery, Transformation and Resilience Plan, the facility will expand CENIEH's capacity to investigate ancient proteins and other biomolecules, positioning the Centre at the forefront of molecular research applied to the fossil record.

Atapuerca, an international benchmark
The combination of an exceptional fossil record and the latest advances in palaeoproteomics reinforces the role of the Sierra de Atapuerca sites as an international benchmark for research into the evolution of large Pleistocene mammals while broadening the possibilities for investigating the past at the molecular level.

"We have recovered proteins from every sample analysed and from every archaeological level, which suggests highly promising prospects for recovering molecular material from the Atapuerca hominins," says María Martinón-Torres, co-director of the Atapuerca excavations and co-author of the study.

“And proteins do not only provide information on taxonomy and phylogeny; they also open an entirely new window for exploring metabolic and physiological questions,” adds Amanda Gutiérrez Carbajal, first author of the study, which stems from her doctoral thesis.

It is the first doctoral thesis in palaeoproteomics linked to the Atapuerca Research Team (EIA) at the University of Burgos. It was co-supervised by María Martinón-Torres, Elena Santos, researcher at the UCM-ISCIII Joint Centre for Human Evolution and Behaviour and affiliated scientist at CENIEH, and Tomàs Marquès-Bonet, researcher at the Institut de Biologia Evolutiva (IBE, CSIC-UPF).

The study was carried out within the framework of the European Marie Skłodowska-Curie PUSHH network and received funding and support from Fundación Atapuerca–Reale through a research grant awarded to Amanda Gutiérrez Carbajal, as well as from the Spanish Ministry of Science, Innovation and Universities through project PID2024-156477NB-C32. The fossil material analysed was recovered during the Sierra de Atapuerca excavation campaigns, funded by the Regional Government of Castilla y León.