Spatial behavior of humans across scales: Mobility – Migration – Dispersal

Abstract

Dispersal events of early humans are diagnosed on the basis of evidence of their presence in time and space, i.e. spatiotemporal shifts in the geographical distribution of hominin fossils. Corresponding to the punctuated distribution of the evidence large scale shifts like Out of Africa events and the initial occupation of the Eurasian continent are predominantly described on large spatial and temporal scales. For modelling purposes, diffusion models directed by features of the environment seem to be considered appropriate to reflect dispersal on such scales. Large scale shifts result, however, from regional shifts of populations and seasonal and/or rather local mobility patterns of groups. They need to be studied on smaller scales and they require more sophisticated quantitative models for spatiotemporal movement patterns. Two basic strategies of mobility of hunter-gatherer groups are distinguished, i.e. logistical and residential strategies. A residential strategy is pursued when resource availability is predictable and does not undergo major shifts, while humans follow a logistical strategy, when resource distribution is patchy and changes radically in a seasonal manner. Hominin groups should therefore adopt different mobility strategies, depending on the extent of seasonal shifts in habitat productivity. The resulting hypothesis is tested by linking the Neanderthal archaeological record with seasonal shifts in habitat productivity around the last interglacial. Both strategies moreover involve different spatial requirements and should therefore lead to different migration behaviors. Migrations will be targeted towards areas with improved resource availability. Moreover, particular routes can be inferred. Migration routes which are not entirely circular (i.e. do not involve returns to the exact point of departure) lead to dispersal. On this level, encounters with other groups and as well as human and non-human competitors should be integrated. The interpretation of dispersals resulting from group based mobility strategies and seasonal migrations requires more sophisticated modelling approaches, than represented by diffusion models. Environmental models should reflect changes in food resource availability, e.g. by being based on relative changes in productivity and a migration analysis of large herbivores. In such environments, groups of agents should pursue mobility strategies and chose them in accordance to resource availability. Therefore, agents should explore their environment through movement and vision. They should monitor the actual state of the environment and share this information with other group members. Furthermore, they should be able to save past states of the environment within their exploration area to decide the appropriate mobility strategy. In this contribution a variety of quantitative models will be presented. Furthermore, we examine links between them and explore their potential to be transferred into an agent-based modelling context.