Inter-band connectivity and climate shaped Neanderthal extinction and Homo sapiens dispersal.

To what extent Neanderthal extinction was triggered by climate change or the arrival and dispersal of Homo sapiens, and by which mechanisms, remains unresolved. Here, based on how climate-driven changes affected habitat favourability for primary and secondary consumers and Net Primary Productivity, we estimate carrying capacity, herbivore biomass and intra-guild predation pressure during the time Neanderthals and H. sapiens lived in Europe (55-30 ka BP). These spatially explicit estimates were incorporated into an agent-based model simulating human demographic dynamics under various scenarios. Results indicate that carrying capacity changes cannot explain Neanderthal extinction at a continental scale, though they are essential to understanding spatiotemporal distribution patterns of both human species. Conversely, the arrival of H. sapiens increased Neanderthal extinction likelihood without requiring a selective advantage. Due to the successive demographic expansions and contractions, group connectivity emerges as the key factor shaping population stability in both species. These findings support that Neanderthal disappearance and H. sapiens dispersals were interconnected demographic processes.