Simulating Palaeolithic Human Dispersal Using Human Existence Potential and Constrained Random Walk Model

Our knowledge regarding the history of mankind and the way that led us from Africa to Europe shows gaps in time and space, despite intensive research. Archaeological discoveries, genetic analyzes or dating provide novel results, which, however, do not always fit into the assumed migration process and cause controversy.To estimate the settlement in regions and time periods without archaeological information or to test hypotheses, numerical human dispersal models can provide answers. The expansion of the Paleolithic hunter-gatherers is a complex and non-linear process influenced by many factors, such as environmental conditions, resource occurrences, population sizes, social components like conflict or exchange, or the presence of other species. One crucial factor for the dispersal is the climate, which determines the living conditions of humans as well as food and water resources. For the quantitative evaluation of the settlement and spread of Paleolithic hunter-gatherers, two numerical models are developed, the Human Existence Potential (HEP) and the Constrained Random Walk Model (CRWM). The HEP allows a static analysis of the habitats of a human culture under climatic and environmental conditions. By using logistic regression, archaeological and climatic data are combined in order to determine a spatial potential for settlement. The HEP is then adjusted by the environmental conditions, such as the topography, glaciers or water bodies, which influence the accessibility of the resources. In addition to the spread, the HEP is used to determine contact probabilities and regionalizations, and the influence of climate changes. The CRWM is a dynamic model that simulates the dispersal of populations through the individual movement of humans. The human movement is described by a stochastic differential equation, i.e. it consists of a deterministic drift and a stochastic component. The direction of the drift is determined by the HEP and other humans, whose presence has both positive effects, since they ensure survival, and negative effects, since they consume the available resources. The stochastic movement reflects the individuality and unpredictability of human behavior. In addition, births and deaths are integrated in the CRWM. The likelihood of both depends on the size of the population and the resources available. Both models are calibrated, validated, tested and then applied to case studies. In a first case study, it is shown that the Solutrean in western Europe were cut off by an environmental barrier from the Epigravettian in eastern Europe during the Last Glacial Maximum. The expansion and contact within the Solutrean took place along the coast of Iberia, with corridors opening up inland in times of favorable climate. Another case study shows that the first phase of immigration into Europe of the modern humans of the Aurignacian came to an end in northern Iberia. The environmental conditions prevented them from spreading further south. The Neanderthals, who populated the Iberian Peninsula at the time, were well adapted to the environmental conditions there and colonized large areas of Iberia. Due to the climate change caused by an Heinrich event, Neanderthal social networks collapsed. This particularly affected the north and south of Iberia. Assuming the Neanderthals lived in significantly lower population densities than modern humans, the Heinrich event presumably led to a complete extinction of the Neanderthals on the Iberian peninsula. Overall, it can be concluded that the extinction of the Neanderthals in Iberia can be attributed more likely to the effects of an Heinrich event than to the appearance of modern humans