The advances during the last few decades of research have revealed that Neanderthals colonized a vast territory that stretched from Spain to Siberia. The earliest Neanderthals in Asia likely arrived there from the west shortly before MIS 6 and were probably separated from European Neanderthals until glaciers retreated. From MIS 5d-a, we continuously find genetic and archaeological connections between European and Siberian Neanderthals.
Despite our current understanding of Neanderthal population history across Eurasia, we still have limited knowledge about the routes taken and the behavioral adaptations required for that journey. Dramatic paleogeographic changes occurred in Eurasia during the period of hypothesized Neanderthal dispersals. Specifically, the formation of ice-dammed lakes in Siberia during cooling phases prior to MIS 3 led to re-routing of river drainage systems and the formation of new rivers due to outburst flow. Considering pioneers colonizing new landscapes often use landmarks such as rivers to enable dispersal, these new watercourses may have facilitated the long-distance movements of Neanderthals suggested by the genetic and archaeological records.
We created paleogeographically realistic agent-based models to simulate dispersal of Neanderthal populations between MIS 6 and MIS 3. Using cost surfaces derived from elevation, climate, hydrological, and glacier data, we explore possible paths that Neanderthals may have taken in Eurasia under different paleogeographic and climatic scenarios. This allows us to test hypotheses about when and how dispersal eastward across Eurasia occurred leading up to the Last Glacial Maximum.
Our results demonstrate that rivers were indeed likely conduits for dispersal across Central Asia between MIS 6 and MIS 3. This is contrasted by highly redundant movement during periods of no glacial outburst and relatively restricted movement when paleolakes would have been at their peak. By running the simulations many times, we identify those routes that are most common. These findings could help direct archaeological survey to find new Paleolithic sites, allowing us to ground truth the model and document important information about the behaviors and technologies required by hominins to disperse across Eurasia.
This study is one of the first to explicitly address the role of large-scale paleogeographic changes in structuring the dispersal of hominins across Eurasia. Furthermore, our model does so in a more realistic way than traditional least-cost path analyses. As such, this study is an important step to helping us understand the behaviors and adaptations required by hominins to expand across this vast region. By characterizing Neanderthal dispersal across Eurasia, we can crucially advance our understanding of how extreme past geographics affected our ancestors’ movements and help clarify our understanding of Neanderthal behavioral and cultural evolution during their last expansion before their extinction.
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