Did Neandertals and anatomically modern humans coexist in northern Italy during the late MIS 3?

The main processes invoked to explain the demise of Homo neanderthalensis are the effects of adverse climatic conditions in the northern hemisphere during Marine Isotope Stage 3 (MIS 3) and the outcome of the interaction with Anatomically Modern Humans (AMHs). Evidence for the co-existence of these two hominins, however, is elusive and, therefore, verifying the role which these processes might have played in the extirpation of Neandertals remains a topic of heated debate. A site which can contribute to throw light on the replacement of H. neanderthalensis by AMHs is Riparo Mezzena, a rockshelter in northern Italy, where late Mousterian lithic industries were found in association with human remains. This paper reviews the results of recent investigations on the lithic assemblages and human bones recovered during excavation campaigns which took place in 1957 and 1977. The study of the physical anthropology of the skeletal remains, in conjunction with palaeogenetic analyses on mitochondrial and nuclear DNA, have proven that the occupiers of Riparo Mezzena were Neandertals. The first radiocarbon date for the site, obtained on collagen extracted from a bovid from the lowermost part of the stratigraphic sequence (Layer III) and presented here (34,540 ± 655 ¹⁴C uncal BP), attests that Riparo Mezzena was occupied during the Middle-to-Upper Palaeolithic transition period. The anthropogenic deposits at the site actually accumulated when the nearby site of Grotta di Fumane was occupied by humans who produced Proto-Aurignacian lithic industries. This suggests that Neandertals and AMHs probably co-existed for a short period of time in northern Italy, possibly competing for resources within the confined territory of the Monti Lessini. These findings arising from new research on the collections of Riparo Mezzena have important implications not only for the study of the Middle-to-Upper Palaeolithic transition in Italy, but also for the understanding of the process through which AMHs replaced H. neanderthalensis.