Paleontologists and anthropologists work on very different very different "time steps", don't speak the same language, and don't study the same "objects". These differences have given rise to a book chapter on water. In the East African Rift, water is the key resource in socio-ecosystems of the alternating highland and lowland socio-ecosystems. Our observations on water sites from northern Ethiopia to northern Kenya, from the very distant past (over a million years ago) to the present and suggest the importance of this resource. Pearls of life, refuges, evolutionary cul-de-sacs, the "water places" of arid zones present a variety of materials that call for interdisciplinary interdisciplinary methodologies. They open up new perspectives on the past socio ecological socio-ecological dynamics of today's deserts, the evolutionary past of our evolutionary past of our ancestors, and more recently on the resilience of today's resilience of today's pastoral societies. Today, however, we are witnessing a paradigm shift: human activities are having an unprecedented impact on water.