A 17-million-year-old whale fossil is helping scientists pinpoint when the East African Plateau started to rise. Determining when the uplift happened has implications for understanding human evolution, scientists say.
Shifts in the Earth’s mantle pushed the East African Plateau upward sometime between 17 million and 13.5 million years ago, researchers report March 16 in the Proceedings of the National Academy of Sciences. Their analysis was based on a Turkana ziphiid fossil first discovered at the edge of the plateau in Kenya in 1964. The beaked whale’s skull was described in a 1975 paper, then misplaced until 2011, when it was rediscovered in a fossil collection kept at Harvard University.
Studying the fossil and the originalfield notes describing its discovery, the team, led by Henry Wichura of the University of Potsdam in Germany, determined that the whale must have swum up an ancient river and gotten stuck. Re-creating features of the ancient river suggests that the whale died and was buried in sediments that sat at an elevation only 24 to 37 meters above sea level. Its skull, however, were found at an elevation of 620 meters. That means the skull, and the sediments that held them, were pushed upward at least 590 meters in the last 17 million years.
Ancient lava flows show the plateau was already pushed upward by 13.5 million years ago, so the fossil find helps pinpoint the uplift to a 3.5 million year period, the researchers conclude. They note that the plateau’s rise changed the climate in the region from dense rainforest to drier open grassland, which may have driven human evolution.