About 1 to 2 million years ago, early humans in East Africa periodically faced very dry conditions, with little or no water in sight. But they likely had access to hundreds of springs that lingered despite long dry spells, allowing our ancestors to head north and out of Africa, according to a groundbreaking study by scientists at Rutgers University-New Brunswick and other institutions.
The international team showed that climate may not play such a primary role in human evolution as is commonly asserted.
“This has very important implications for human evolution,” said Gail M. Ashley, a professor in the Department of Earth and Planetary Sciences at Rutgers. “We’re not saying anything about why early humans left Africa. We’re only saying it was possible to leave Africa by going from one spring to the next and they could travel during dry periods.”
The study, which focuses on the key role of “hydro-refugia,” or water refuges, in East African hominin (early human) evolution and dispersal, was published today in the online journal Nature Communications. Hydro-refugia, a new term coined by the scientists, include springs, wetlands, groundwater-fed perennial streams and groundwater-fed rivers.
The study has global relevance since drylands cover about 45 percent of the Earth’s land mass. The importance of groundwater for the survival of our hominin ancestors during dramatic climate swings could inspire and inform strategies for human resilience to future climate change, the study says.
For several million years, the African climate has fluctuated between wet and dry in 23,000-year cycles. And since most lakes are undrinkable (saline or alkaline) and rivers dry up for large parts of the year in East Africa, where early humans arose, the study focused on the viability of groundwater-fed springs.
Rainwater is stored in large underground aquifers and moves slowly until it seeps out onto the surface as springs. The location of groundwater-fed springs is controlled by geology and the groundwater supply is buffered against climate change, according to Ashley, a geologist whose curiosity about springs prompted the study.
