Africa may be slowly breaking apart—and that same process could explain our fossil record.
Eastern Africa’s Turkana Rift is known both for its rich collection of early human fossils and its intense volcanic activity driven by shifting tectonic plates. Now scientists report that the crust beneath this region has thinned far more than previously recognized, pointing toward the long-term breakup of the African continent—and offering a new explanation for why this area preserves such an extraordinary record of human evolution.
The findings were published in Nature Communications.
A Massive Rift Shaped by Tectonic Forces
The Turkana Rift spans about 500 kilometers across Kenya and Ethiopia and forms part of the broader East African Rift System. This system stretches from the Afar Depression in northeastern Ethiopia down to Mozambique, separating the African tectonic plate from the Arabian and Somali plates. In the Turkana region, the African and Somali plates are slowly moving apart at roughly 4.7 millimeters per year.
This gradual separation, known as rifting, pulls the crust sideways. As it stretches, the ground buckles and fractures, allowing magma from deep within Earth to rise toward the surface.
While some rifts stall before splitting a continent, the Turkana Rift appears to be progressing toward that outcome.
Thinning Crust Signals Advanced Rifting
“We found that rifting in this zone is more advanced, and the crust is thinner, than anyone had recognized,” says study lead author Christian Rowan, a Ph.D. student at Columbia University’s Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. “Eastern Africa has progressed further in the rifting process than previously thought.”
To investigate, Rowan and his team analyzed a high-quality set of seismic data gathered with industry partners and in collaboration with the Turkana Basin Institute, founded by the late paleoanthropologist Richard Leakey. By tracking how sound waves moved through underground layers and combining those results with other subsurface imaging, the researchers mapped sediment structures and determined the depth of the crust beneath the rift.
At the center of the rift, the crust is about 13 kilometers thick. Away from the rift, it exceeds 35 kilometers. This sharp contrast is a clear sign of a process known as “necking.”
“Necking” Marks a Critical Stage of Breakup
The term “necking” refers to how the crust narrows as it stretches, similar to the thin middle section that forms when a piece of saltwater taffy is pulled from both ends. As the crust becomes thinner, it also weakens, which makes continued rifting more likely.
“The thinner the crust gets, the weaker it becomes, which helps promote continued rifting,” Rowan says. Eventually, the crust can split completely.
“We’ve reached that critical threshold” of crustal breakdown, says Anne Bécel, a geophysicist at Lamont and co-author of the study. “We think this is why it is more prone to separate.”
Even so, these changes unfold over vast timescales. The Turkana Rift began opening around 45 million years ago, and researchers estimate that necking began after widespread volcanic eruptions about 4 million years ago. It could take several million more years before the next stage, called oceanization, begins. During that phase, magma will rise through fractures to create new seafloor, and water from the Indian Ocean to the north may eventually flood into the region.
Evidence of Earlier Failed Rifting
The study also uncovered signs of an earlier rifting episode that did not result in a full continental split. Instead, it left the crust thinner and weaker, helping drive the current phase of activity.
“It challenges some of the more traditional ideas of how continents break apart,” says Rowan.
Because the Turkana Rift is the first known active continental rift currently undergoing necking, it provides a rare opportunity to observe this crucial stage of tectonic evolution.
“In essence, we now have a front row seat to observe a critical rifting phase that has fundamentally shaped all rifted margins across the world,” says co-author Folarin Kolawole, who is also with Lamont. These processes are linked to other Earth systems, helping scientists reconstruct past environments, vegetation, and climate. “Then we can use that knowledge to understand what’s going to happen in our future, even on shorter time scales,” says Bécel.
Rethinking the Fossil Record of Human Evolution
The findings also have important implications for understanding human evolution. The Turkana Rift has produced more than 1,200 hominin fossils from the past 4 million years, representing about one-third of all such discoveries in Africa. Many researchers have considered this region a key center of early human evolution.
Rowan and his colleagues suggest a different interpretation.
After widespread volcanic activity around 4 million years ago, the onset of necking caused the land in the rift to sink. This subsidence led to the rapid buildup of fine-grained sediments, which are especially good at preserving fossils.
“The conditions were right to preserve a continuous fossil record,” says Rowan.
This raises the possibility that the Turkana Rift was not uniquely important as a location where human ancestors evolved, but rather a place where geological conditions made it easier to preserve their remains.
That idea remains a hypothesis. “But other researchers can now use our results to explore those ideas,” says Rowan. “In addition, our results can be fed into tectonic models that are coupled with climate to really explore how shifting tectonics and climates influenced our evolution.”
Reference: “Necking of the active Turkana Rift Zone and the priming of eastern Africa for continental breakup” by Christian M. Rowan, Folarin Kolawole, Anne Bécel, Paul Betka and John Rowan, 23 April 2026, Nature Communications.
DOI: 10.1038/s41467-026-71663-x
The research team also includes Paul Betka from Western Washington University and John Rowan from the University of Cambridge.
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