Freshwater springs likely played role in early human evolution

The ability to move and seek out new sources of groundwater in dry periods may have been pivotal to survival and evolution of the human species. By combining geological evidence from the Olduvai sedimentary basin in Northern Tanzania with a hydrological model, researchers have shown that while water in rivers and lakes disappeared as the climate changed, freshwater springs fed by groundwater could have remained active for up to 1,000 years without any rainfall. “A major unknown connected with human evolution in this climatically turbulent environment is the availability of resources, particularly freshwater,” said Dr Mark Cuthbert from the University of New South Wales. “Springs and groundwater-fed habitats could have played a decisive role in the survival and dispersal of hominins in times when potable surface water was limited.” Groundwater in springs could have provided key alternative water in the environment when rivers and lakes were drying up due to salinity, drought and the short-lived flow of streams. Geological evidence suggests springs were active during the driest periods of climate fluctuations that occurred 1.8m years ago. Modelling also showed springs at Olduvai could have stayed active for hundreds of years without rainfall. "As surface water sources became more scarce during a given climate cycle, the only species to survive may have been those with adaptations for sufficient mobility to discover a new and more persistent groundwater source, or those already settled within home range of such a resource," Professor Gail Ashley of Rutgers University said. "Such groundwater refugia may have been sites for intense competition between hominin and other animal species and hence selective pressure favouring those who could maintain access to water, something for which there is no substitute.” Ashley, co-author of the paper published in PLOS One, speculates that in wetter periods, springs may have formed ways of 'bridging' longitudinal dispersal of hominins between larger freshwater bodies or rivers providing a critical resource during hominin migration within and out of Africa. The researchers say that more research in now necessary to test their theory about the role that groundwater may have played in human evolution and dispersal. A spring forward for hominin evolution in East Africa