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Groundwater Access Ensured Hominin Survival

Our ancient ancestors’ ability to move around and find new sources of groundwater during extremely dry periods in Africa millions of years ago may have ensured their survival and the evolution of the human species, according to research published in PLOS ONE.

Geological evidence from the Olduvai sedimentary basin in Northern Tanzania, which formed about 2.2 million years ago, and the results from hydrological modelling revealed that while water in rivers and lakes would have disappeared as the climate changed, freshwater springs fed by groundwater could have stayed active for up to 1000 years without rainfall.

Potable water in rivers or lakes in the region is likely to have been scarce due to salinity, drought and the short-lived flow of streams. “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,” says lead author Dr Mark Cuthbert of The University of NSW’s Connected Waters Initiative and The University of Birmingham.

Geological evidence indicates that the springs were active during the driest periods of climate fluctuations around 1.8 million years ago, a critical period for hominin evolution. Modelling by the researchers also showed that Olduvai’s springs may 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,” said co-author Prof Gail Ashley of Rutgers University. “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.

“Furthermore we speculate that, during 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,” Ashley said.