The sediment at the end of the tunnel: Geophysical research to locate the Pleistocene entrance of Gruta da Companheira (Algarve, Southern Portugal)

Abstract

The ability to exploit the deeper levels of cave systems is regarded as complex human behavior. Evidence that Neanderthals possessed this skill remains limited. The site of Escoural, in southern Portugal, is worldwide renowned for the Upper Paleolithic rock art that was performed in the lowermost level of the cave. The site also preserved Middle Paleolithic sequences in a deep chamber (P1) as well as in an area that today lies outside of the cave (P2). Due to the lack of geoarchaeological analyses, it is currently impossible to clarify whether these materials reflect systematic Neanderthal visits to these site areas. In this study we integrated geoarchaeological data and radiocarbon dating to (i) reconstruct site formation processes, and (ii) explore the interaction between Neanderthals and carnivores at Escoural. Micromorphological, stratigraphic, and geochronological results demonstrate that colluviation moved sediments and archaeological finds from upper cave chambers into P1. This process likely mixed separate and distinct assemblages, possibly leading to co-occurring high concentrations of carnivore coprolites and lithic artifacts. In contrast, P2 preserves in situ Neanderthal occupations alternating with carnivore visits. Neanderthal foragers used this area when it was a large chamber located close to the original cave entrance, which was subsequently lost due to roof collapses and likely impacted by modern quarrying activities. These findings align with broader Eurasian patterns indicating that Neanderthals primarily used well-lit karstic cavities rather than deep, enclosed spaces. Moreover, this study underscores that post-depositional processes may have profound impacts on our interpretation of Neanderthal and carnivore cave use.