Rapid environmental changes may have driven human evolution, occurring one after the other in east Africa about two million years ago, American researchers say.
"These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years," said Clayton Magill, study co-author and geosciences researcher at Penn State University.
Katherine Freeman, professor of geosciences at the varsity said: "There is a view Africa was the 'Great Drying' when the environment slowly dried out over three million years."
"But our data show that it was not a grand progression towards dry. The environment was highly variable," added Magill. "Early humans went from having trees available to having only grasses available in just 10 to 100 generations, and their diets would have had to change in response," he said.
"Our data are consistent with these hypotheses. We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use," said Magill, according to a Penn statement.