Chronostratigraphy of the Middle-to-Upper Paleolithic Transition in the Iberian Peninsula

The complex environmental history of Isotope Stage Three carries the implication that cave and rockshelter sites containing deposits from the time of the Middle-to-Upper Paleolithic transition must have been significantly affected by syn- and post-depositional disturbance processes. A detailed taphonomic critique of the stratigraphic successions, of the integrity of archeological levels, of the composition of industrial assemblages, and of the associations between samples selected for dating and the events or processes they are supposed to date is therefore an absolute requirement in assessing the tempo and mode of that transition. Once the evidence yielded by the key Iberian sites is passed through such a taphonomic filter, and the chronometric results obtained by different dating methods are reduced to a single, calendar timescale, and taken with due consideration of the inherent level of statistical uncertainty, a rather clear picture emerges. Regions located north of the Ebro divide follow the general European pattern, where the transition is a two step process featuring, first, the emergence out of local Middle Paleolithic roots of different Neandertal-associated early Upper Paleolithic technocomplexes (in the case of northern Iberia, the Châtelperronian, known from Morín, in the west, to l’Arbreda, in the east) and, second, the replacement of the latter by the Protoaurignacian, which takes place ca. 42 ka BP (in calendar years), i.e., at about the time when modern human populations are first recorded in Europe. South of the Ebro divide, a Neandertal-associated Middle Paleolithic survives for several millennia more, and is eventually replaced by the Evolved Aurignacian (Aurignacian II), an event that, from Alicante, in the east, to Portugal, in the west, takes place no later than ca.35 ka BP (in calendar years). The paleoenvironmental record suggests that this delayed survival of Middle Paleolithic Neandertals in southwestern Iberia is related to a prolonged period of ameliorated climatic conditions that, at least in littoral areas, may have favored the expansion of woodland landscapes.