Reassessing palaeoenvironmental conditions during the Middle-to-Upper Palaeolithic transition in the Cantabrian region (Southwestern Europe)

Climatic and environmental changes have been commonly proposed as driving factors behind the decline of Neanderthals in Europe. The Cantabrian region, in northern Iberia, is a key area for understanding the replacement of Neanderthals by Anatomically Modern Humans, where an early disappearance or Neanderthals in relation to other areas of Iberia has been proposed. To evaluate how climate might have influenced human behaviour during Marine Isotope Stage 3, an accurate review of palaeoecological conditions is required. For the first time, an assessment of the regional available terrestrial proxies linked to archaeo-palaeontological sites, including small vertebrate assemblages, pollen sequences, charcoal data and stable isotope studies on macromammals is undertaken in this region. In addition, records from macrofaunal assemblages and glacial records have also been considered. To standardise the information and allow inter-site comparison, data from pollen and small vertebrate sequences were transformed into quantitative climatic estimations of temperature and precipitation. Results show highly variable climatic shifts between archaeological levels, being consistent with the climatic fluctuations observed in the marine and ice core records. Small mammal assemblages reveal a mosaic landscape of open meadows followed by scattered forested areas. A progressive trend towards aridity from the end of the Mousterian to the early Aurignacian is reflected by changes in arboreal pollen, macromammal species and stable isotopes evidence on ungulates consumed by Neanderthals and Anatomically Modern Humans in the region. This review suggests a decrease in temperatures and rainfall from 48,000 to 44,000 cal BP (after Heinrich Event 5) which coincides with the late Neanderthals in the region and followed by a populational hiatus until 43,000 cal BP. Despite the multiple intra-site environmental proxies available, this study has challenged the fragmentary regional record during this key period for human evolution and reveals that further research is needed to obtain a complete regional high-resolution palaeoenvironmental and palaeoclimatic reconstruction