Spatial resilience and population replacement in Europe during MIS 3: a comparative study of Neanderthals and H. sapiens

Homo sapiens dispersed out of Africa several times during the Late Pleistocene. The most recent dispersal event, which began around 60,000 years ago, resulted in the permanent establishment of Sapiens populations in Europe, followed by the disappearance of Neanderthals from the archaeological record. Various hypotheses suggest that the process of population replacement in Europe was influenced by climate change, habitat dynamics, demographic processes, and/or competitive exclusion. To test these hypotheses, we use habitat suitability modeling and GIS tools to predict the optimal distribution of Neanderthal and Aurignacian populations in Europe during stadial and interstadial events of Marine Isotope Stage 3 (MIS 3) and reconstruct their regional networks. The models show that while relatively more suitable habitat was available for Homo sapiens under interstadial conditions, both groups were affected by climate change resulting in shifts in the location of optimal regions and concomitant changes in the social networks that connected them. Our analysis indicates that optimally suitable habitat persisted across the potential ranges of both species despite climate change. Climate stress alone is not indicated as a cause of Neanderthal's extinction, therefore. Several “core” regions are identified that could have sustained a pattern of demographic resilience, allowing populations to rebound and re-expand during climate upturns, notably in southwestern Europe and, in the case of Neanderthals, in southern Iberia. The optimal regions and the networks they form indicate a potential for interaction between Neanderthals and Sapiens across Europe. While their ranges overlap, however, there are subtle differences in habitat preference that mitigate the potential impact of interactions, suggesting that competition for resources may not have been the primary cause of Neanderthal extinction. The results also suggest regional differences in the combination of stressors that could have influenced Neanderthal extinction, with Sapiens potentially playing a more active role in Western Europe, where regional overlaps impinge on the “core” regions. In Southeastern Europe, where regional connection within the Neanderthal network were relatively tenuous, Neanderthal groups may have been more vulnerable to random events and demographic pressures, including genetic assimilation. A more complex interplay of climate change, population dynamics and demographic factors is suggested to have contributed to the eventual disappearance of the Neanderthals. Ultimately, the study suggests that the process of population replacement in Europe is the result of the complex and regionally differentiated interplay of climate, geography, demography and interspecific interactions rather than a homogeneous, climate-driven process. • Geostatistical tools facilitate Species Distribution Model comparison. • Stadial/interstadial events produce contrasting patterns in habitat quality for H. sapiens and Neanderthals. • Overlapping habitat use is predicted across H. sapiens and Neanderthal ranges. • Connectivity between optimal regions is relatively weak for Neanderthals. • Population replacement across Europe was likely not a uniform process.