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A sculptor's rendering of the hominid Australopithecus afarensis that lived 3.2 million years ago in ... More Africa.
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An international team of researchers investigated how Earth’s mantle activity created an uplift between what is now the Arabian Peninsula and Anatolia about 35 to 20 million years ago.
The resulting land bridge enabled the early ancestors of animals such as giraffes, elephants, rhinoceroses, cheetahs, and even humans, to leave Africa, ending a 75-million-year-long isolation of the continent.
"This study has relevance to the question of 'How did our planet change, in general? What are the connections between life and tectonics?’" says Thorsten Becker, a study co-author and professor at the Jackson School’s Department of Earth and Planetary Sciences and Institute for Geophysics, University of Texas.
The full story begins 70 to 60 million years ago, when a slab of rock sliding into Earth’s mantle melted, creating a plume that reached the surface some 30 million years later. The mantle plume pushing upwards, coupled with the collision of tectonic plates between Africa and Asia, created an uplift that contributed to closing the ancient Tethys Sea, splitting it into what is now the Mediterranean and Arabian Seas, and created a landmass that bridged Asia and Africa for the first time. In a similar way Iceland is today above sea level because it sits atop a mantle plume and between two tectonic plates.
The study’s lead author Eivind Straume analyzed the wide-ranging consequences of this geologic activity while he was a postdoctoral fellow at the Jackson School. He says the appearance of the land bridge and evolution of early hominids go hand in hand.
"The shallow seaway closed several million years before it otherwise likely would have due to these specific processes—mantle convection and corresponding changes in dynamic topography," explains Straume, who is now a postdoctoral fellow at the Norwegian Research Center and The Bjerknes Center for Climate Research.
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