Speleothem record attests to stable environmental conditions during Neanderthal–modern human turnover in southern Italy

The causes of Neanderthal–modern human (MH) turnover are ambiguous. While potential biocultural interactions between the two groups are still little known, it is clear that Neanderthals in southern Europe disappeared about 42 thousand years ago (ka) after cohabitation for ~3,000 years with MH. Among a plethora of hypotheses on Neanderthal extinction, rapid climate changes during the Middle to Upper Palaeolithic transition (MUPT) are regarded as a primary factor. Here we show evidence for stable climatic and environmental conditions during the MUPT in a region (Apulia) where Neanderthals and MH coexisted. We base our findings on a rare glacial stalagmite deposited between ~106 and ~27 ka, providing the first continuous western Mediterranean speleothem palaeoclimate archive for this period. The uninterrupted growth of the stalagmite attests to the constant availability of rainfall and vegetated soils, while its δ13C–δ18O palaeoclimate proxies demonstrate that Apulia was not affected by dramatic climate oscillations during the MUPT. Our results imply that, because climate did not play a key role in the disappearance of Neanderthals in this area, Neanderthal–MH turnover must be approached from a perspective that takes into account climatic and environmental conditions favourable for both species. Unstable and harsh climates have been implicated as partial causes of Neanderthal demise. Here a speleothem palaeoenvironmental record spanning the Middle to Upper Palaeolithic transition attests to stable and moderate conditions in the Mediterranean during this time suggesting a more complicated picture than previously thought.