Researchers at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) have led a study, recently published in the Journal of Human Evolution, on the diet of individuals at the Sima de los Huesos site (Sierra de Atapuerca, Burgos) by reconstructing their eating habits based on dental wear. In addition, the study examined whether the dental wear reflects the environmental conditions of the glacial period known as MIS 12, one of the coldest globally, which would have favoured a significant expansion of semi-arid vegetation on the Iberian Peninsula around 450,000 years ago.

The hominids from the Sima de los Huesos who lived in Atapuerca during this glacial period are known to be the closest relatives of Neanderthals. Beyond the morphological similarities shared by both groups, they have also been assumed to have had similar dietary behaviours, typically considered hypercarnivorous. Therefore, one might expect a wear pattern similar to that observed in populations living in cold environments, where animal protein was the main dietary source. But the results indicate differentiated attrition due to a comparable intake of plant and meat resources.

“In addition, the maxillary molars of the SIMA individuals are characterized by a more pronounced inclination of the wear facets compared to the other groups, which suggests a less abrasive diet,” says the article's lead author, Laura Martín-Francés, a researcher at CENIEH and Monash University (Australia).

Together, these findings suggest that the population of Sima de los Huesos inhabited an environment dominated by open forest landscapes, with relatively more stable environmental conditions, in contrast to the harsh conditions traditionally associated with MIS 12. The findings also suggest that their diet was varied, challenging the interpretation of a diet dominated exclusively by meat.

Digital analytics
The analysis of tooth wear included 16 maxillary molars, which were studied using micro-computed tomography (micro-CT). Three-dimensional models of each tooth were generated and, using specific software (PolyWorks® V. 12, InnovMetric, Quebec, Canada), the wear facets were identified, digitized and measured.

A comparative sample was also included, comprising Neanderthals from different geographic regions and time periods, as well as modern hunter-gatherer populations, including Alaskan Inuit and Australian Aboriginals.

Dental macro-wear
Macrowear on the teeth reflects dietary adaptation, as it results from specific chewing movements used to process foods with different properties. During chewing, the jaw performs two main movements that create wear facets — flat, polished surfaces — on specific areas of the tooth surface.

The transverse movements of the jaw that crush hard and abrasive plant foods produce a higher proportion of wear facets on the lingual side of the upper molars. In contrast, individuals with higher meat consumption typically show more vertical mandibular movements, resulting in a greater proportion of wear facets on the buccal surfaces. This not only reflects dietary preferences, but also ecological conditions, particularly the availability of food. Thus, different species that inhabit similar environmental settings exhibit comparable wear patterns, whereas populations inhabiting cold environments, where diets were more restricted and primarily based on animal resources, show distinct wear.

"Our study of the dental wear of the Sima de los Huesos hominids has observed a similar proportion of facets on the surface of the molars, indicating a comparable consumption of vegetable and meat products and, furthermore, challenging the traditional view that defines them as strictly hypercarnivorous groups", concludes Martín-Francés.

This work is supported by the Horizon Program-Marie Sklodowska-Curie Actions of the EU Ninth programme (2021—2027) under the HORIZON-MSCA-2021-PF-01-Project: 101060482; the Spanish Ministry of Science and Innovation and European Regional Development Fund “ERDF A way of making Europe” (projects PID2021-122355NB-C31, PID2021-122355NB-C32, PID2021-22355NB-C33).