Linking prey biomass and Neanderthal population in a challenging upland landscape in the Late Pleistocene: the upper valley of the Lozoya River (Spain)

Abstract Context The mountainous and seasonally variable landscapes of the Late Pleistocene period posed major challenges for hunter-gatherers, shaping their ecological strategies and demographic limits. In the central Iberian Peninsula, the landscape played a decisive role in shaping herbivore communities and human settlement patterns. While the Iberian Peninsula has a rich Paleolithic record, MIS 5 archaeological sites are scarce in its central region, which includes two plateaus and the Sistema Central mountain range. This area likely had unfavorable ecological conditions for human habitation during parts of the Pleistocene, so people were confined to valleys and localized ecological refuges. In this context, the upper valley of the Lozoya River in Madrid, Spain, is home to the Calvero de la Higuera sites, which provide evidence of Neanderthal occupation in a sub-Mediterranean highland environment; Objetives This study assesses how such a challenging landscape could sustain local Neanderthal populations through large prey resources; Methods Using species distribution models (SDMs) based on fossil occurrences and paleoclimatic data, we estimated the habitat favorability, population density, and biomass of nine large herbivorous mammals recorded at Cueva del Camino (Layer 05, ~ 90 ka); Results The SDMs revealed significant differences in habitat favorability among species, with Cervus elaphus exhibiting the greatest favorability and Rupicapra pyrenaica the least. Incorporating habitat favorability into biomass estimates significantly reduced the potential presence of prey, highlighting the spatial limitations of upland ecosystems. Comparisons with modern ecosystems (e.g., Serengeti, Kruger and Hwange) suggest that the results are ecologically feasible; Conclusion Our estimates suggest that the upper valley of the Lozoya River had the potential ecological capacity to support between 14 and 33 Neanderthal individuals. This highlights the delicate ecological balance that may have enabled recurrent Neanderthal presence in the challenging upland environments of central Iberia.