The beginning of groundwater use by hominins and its key to migrations by Homo erectus out of Africa

Despite growing acceptance of the importance of groundwater use by hominins, there has been little hydrogeological investigation into the controls on groundwater availability as relevant to their evolution and geographic dispersal. This study integrates available fossil and stone tool data with hydrogeological landscape reconstruction and conceptualisation to develop understanding and constraints on the earliest use of groundwater by hominins and early migrations between Africa and Eurasia. It is proposed that the first bipedal human ancestors, appearing in the fossil record in Central and East Africa between 6 and 7 Ma, learned from other mammals how to find and access shallow groundwater in ephemeral streambeds. The first evidence of hominin associations with groundwater discharge from springs is from around 2–4.5 Ma in the East African Rift System (EARS), these locations likely being critically stable hydro-refugia within the driest parts of precession-dominated climatic cycles. The first migrating hominin species appears to have been Homo erectus , with those in the EARS leaving in waves as small bands from around 1.9 Ma at the end of a humid period in the Arabian Peninsula. It is proposed that the most hydrologically plausible routes linking the EARS to Eurasia are via Red Sea crossings and then through the Arabian Peninsula moving along the strike of regional aquifers which would have provided perennial groundwater even over long climatically arid periods. The paper demonstrates the fundamental importance of groundwater for early hominin communities during a critical period in the evolution of human physiology and consciousness.