The availability of water influences the evolution of life as well as the evolution of the Earth’s land surface. Until recently, the role of geomorphological and biological (geo-bio) processes including their interactions and co-evolution have been poorly understood for extremely water-limited (hyper-arid) environments. This emerging field lies at the nexus of weathering, soil (crust) formation and erosion but also involves landform evolution, which creates barriers or corridors for life across varied geological time scales. To facilitate interdisciplinary research at this geo-bio interface, we established the DFG funded Collaborative Research Centre CRC1211 (Earth–Evolution at the Dry Limit, funded since 07/2016). The natural laboratories we use for this work are the hyper-arid cores of the Atacama and Namib deserts with the main objective to gain improved understanding of the geo- and biosphere evolution in hyper-arid environments and to evaluate interactions between these spheres. We hypothesize that phases or events of higher water-availability (by fog, dew or rain) are the key drivers of geo-bio co-evolution. Furthermore, we hypothesize that barriers of geological, geomorphological, and climatic origin are the main controls on present-day biodiversity at various hierarchies including ecosystem dynamics. To test both hypotheses, we apply state-of-the-art methods from (phylo-) genetics, molecular biology, biogeography, ecology, soil sciences, geomorphology, meteorology, (palaeo-) climatology, (isotope-) geochemistry and geochronology to shed new light on the trajectories and thresholds of the evolution and isolation of life. New results of this research endeavour will be presented during the lecture.