Preliminary palaeoecological reconstruction of the Ruidera site (Middle Pleistocene, Southern Iberian sub-plateau).

The palaeoanthropological site of Ruidera [1], discovered in 2018, provides a unique high-resolution window into the ecosystem dynamics of the Iberian Peninsula during the late Middle Pleistocene (ca. 300 kyr). Characterized by remarkable abundance and preservation of human and macro-mammal fossils, the assemblage includes a diverse suite of taxa, including European tahr, deer, horses, and a dense guild of carnivores such as lions, leopards, lynxes and wolves, as well as some mesofauna remains such as rabbits and birds. This study presents a preliminary palaeoecological reconstruction of the site through stable isotope analysis (δ¹³C, δ¹⁸O) of tooth enamel across six different taxa, including carnivores, herbivores and hominins.

This study’s purpose is to make a first approximation to the ecosystem present in Ruidera during this period, focusing on the hypothesis that it could present a Mediterranean landscape similar to the current one and typical of the Iberian Peninsula, but not discarding some potentially small variations in comparison to other Iberian records, given its more southern latitude. The isotopic data available from other Middle Pleistocene Iberian sites (Punta Lucero, northern Spain [2]; and Sierra de Atapuerca complex: Trinchera Dolina (TD10+TD11) [3], Sima de los Huesos [3,4] and Trinchera Galería (GII+GIII) [3]) will be compared to that obtained for Ruidera.

The Ruidera isotopic data infer a Mediterranean ecosystem defined by a degree of aridity previously unrecorded in the Iberian Middle Pleistocene, at least through stable isotope analysis. The significantly positive δ¹³C values suggest a water-stressed environment, likely representing one of the most xeric records for this chronology in the Iberian Peninsula. Furthermore, δ¹⁸O values align closely with those from the coastal site of Punta Lucero; yet diverge considerably from the more continental inland records of the Sierra de Atapuerca complex. This could suggest a distinct regional climatic pocket for Ruidera, influenced by both Mediterranean aridity and specific topographic effects.

Taphonomic analysis and the faunal list indicate an environment characterized by the ecological biases of mountainous terrain, with a strong signal of accumulation by carnivores. Within this framework, the trophic position of the Ruidera hominin was evaluated. The results indicate that the hominin occupied an isotopic niche closely similar to that of the leopard (Panthera pardus) at the same site. This suggests a specialized, high-protein diet consistent with other European Middle Pleistocene records [5].

In conclusion, the Ruidera site stands out as a unique climatic outlier within the Middle Pleistocene Iberian record. The inferred environment is one of a quite arid Mediterranean landscape where hominins habited within a carnivore-dominated community. These preliminary results underscore the environmental heterogeneity of the Iberian Peninsula and the capacity of Middle Pleistocene fauna and human populations to adapt to different paleoclimatic conditions.

References:

[1] García-Martínez et al. 2022. Cuaternario y Geomorfología. 36, 7–35. https://doi.org/10.17735/cyg.v36i1-2.90422 

[2] Domingo et al. 2017. Quaternary Science Reviews. 169, 243–262. https://doi.org/10.1016/j.quascirev.2017.06.008

[3] García García et al. (2009). Journal of Archaeological Science. 36, 1142–1151. https://doi.org/10.1016/j.jas.2008.12.018

[4] García García et al. (2015). PLOS ONE. 10, e0142895. https://doi.org/10.1371/journal.pone.0142895

[5] Ecker et al. (2013). Journal of Human Evolution. 65, 363–373. https://doi.org/10.1016/j.jhevol.2013.06.013