SYDNEY, AUSTRALIA—Freshwater springs fed with groundwater may have been key to the survival and evolution of human ancestors, according to a new study of geological evidence from the Olduvai Basin in northern Tanzania. “A major unknown connected with human evolution in this climatically turbulent environment is the availability of resources, particularly fresh water,” Mark Cuthbert of the University of New South Wales and the University of Birmingham told Science Daily. Geologic evidence suggests that the springs in the region were active some 1.8 million years ago, a critical period in human evolution, and a period when climate fluctuations could have dried up rivers and lakes. “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,” added Gail Ashley of Rutgers University.