East Africa splits
A rift that made the savanna — and preserved our fossils
See it on the timeline →In depth
The rift system extends over 6,000 kilometres and is an active continental break-up: the Somali plate is pulling away from the rest of Africa. Geologically, it produced a topography that changed rainfall patterns and gradually replaced forest with a mosaic of savanna and woodland through the Neogene — the environment in which walking upright became an advantage. The consequence for science is at least as important: rapid sedimentation and datable ash layers give a quality of fossil preservation found nowhere else. Our knowledge of human origins is skewed towards East Africa partly because that is where the preservation is good.
For children
Africa began splitting along a line running south from the Red Sea. That raised high escarpments that blocked the rain, and the forest behind them became savanna. Lakes and volcanic ash gathered in the rift and buried whatever died there — which is why nearly all human fossils come from this one place.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org