Melbourne, Sep 11 (IANS): Our ancient ancestors' ability to find new sources of groundwater during extremely dry periods in Africa millions of years ago may have been the key to their survival and the evolution of the human species, a new study shows.

The study combined geological evidence from the Olduvai sedimentary basin in Northern Tanzania, formed about 2.2 million years ago and results from a hydrological model.

While water in rivers and lakes would have disappeared as the climate changed due to variations in the Earth's orbit, freshwater springs fed by groundwater could have stayed active for up to 1,000 years without rainfall, the researchers said.

"A major unknown connected with human evolution in this climatically turbulent environment is the availability of resources, particularly freshwater," said lead author Mark Cuthbert from the University of New South Wales in Australia.

Potable water in rivers or lakes in the region is likely to have been scarce, owing to salinity, drought and the short-lived flow of streams. Groundwater may have provided a key alternative potable resource for sustaining life in this environment.

"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," Cuthbert noted.

Geological evidence pointed to the springs being active during the driest periods of climate fluctuations that occurred around 1.8 million years ago, a critical period for hominin evolution.

The study appeared in the journal PLOS ONE.