The stage was set for the emergence of hominids - the ancestors of humans and great apes - 14 million years earlier than previously thought, according to a researcher at The University of Western Australia.
This follows a study that involved Australian Research Council Future Fellow Dr Tony Kemp, of UWA's School of Earth and Environment and Centre for Exploration Targeting, who conducted radiometric dating of volcanic ash beds in the Great Rift Valley of East Africa.
The western rift contains lakes such as Tanganyika and the eastern section is dominated by Mount Kilimanjaro. The valley is regarded as the birthplace of human beings.
Dr Kemp is co-author of a paper published recently in Nature Geoscience. The study was undertaken with researchers from James Cook University, led by Dr Eric Roberts, and organisations in the United States.
"We found new evidence for the earliest evolution of the rift system, which occurs along the boundary between two diverging tectonic plates," Dr Kemp said.
"The system uplifts the eastern part of Africa and is effectively splitting the continent in two. Our dating suggests that rifting had begun to modify the landscape and re-route the major river systems - the Congo, Nile and Zambezi - at a much earlier stage in the evolution of the African continent.
"This led to climate shifts and the formation of ecological corridors that ultimately enabled human evolution."
The group included a palaeontologist from Ohio University who studied new fossil material recovered in the ash sediments.
The group's joint findings provide a better understanding of climate change, animal evolution, and the development of Africa's unique landscapes which resulted from the broad uplift of East Africa. Scientists now think this happened as far back as 25 to 30 million years ago.