Climatic conditions for the last Neanderthals: Herpetofaunal record of Gorham's Cave, Gibraltar.

Gorham's Cave is located in the British territory of Gibraltar in the southernmost end of the Iberian Peninsula. Recent excavations, which began in 1997, have exposed an 18 m archaeological sequence that covered the last evidence of Neanderthal occupation and the first evidence of modern human occupation in the cave. By applying the Mutual Climatic Range method on the amphibian and reptile assemblages, we propose here new quantitative data on the terrestrial climatic conditions throughout the latest Pleistocene sequence of Gorham's Cave. In comparison with current climatic data, all mean annual temperatures were about 1.6-1.8 degrees C lower in this region. Winters were colder and summers were similar to today. Mean annual precipitation was slightly lower, but according to the Aridity Index of Gaussen there were only four dry months during the latest Pleistocene as opposed to five dry months today during the summer. The climate was Mediterranean and semi-arid (according to the Aridity Index of Dantin-Revenga) or semi-humid (according to the Aridity Index of Martonne). The atmospheric temperature range was higher during the latest Pleistocene, mainly due to lower winter temperatures. Such data support recent bioclimatic models, which indicate that high rainfall levels may have been a significant factor in the late survival of Neanderthal populations in southern Iberia. The Solutrean levels of Gorham's Cave and climate records from cores in the Alboran Sea indicate increasing aridity from Marine Isotope Stage (MIS) 3-2. Because Neanderthals seem to have been associated with woodland habitats, we propose that lessening rainfall may have caused the degradation of large areas of forest and may have made late surviving Neanderthal populations more vulnerable outside southern refuges like the Rock of Gibraltar.