1 week Ago By David Bressan, Senior Contributor
A sculptor's rendering of the hominid Australopithecus afarensis that lived 3.2 million years ago in ..
. More Africa. 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 brings together existing research spanning plate tectonics, mantle convection, topography and paleogeography, evolutionary anthropology, mammal evolution, climate evolution, and ocean circulation, among other topics, to tell a cohesive story of the wide-ranging effects of these mantle dynamics. "What are the connections between life and tectonics?” summarizes 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.
Without the mantle plume, Africa and Asia may have remained isolated for much longer, and the animals that made their way into and out of Africa, including our ancestors, could have been much different. Several million years before the land bridge had completely closed, the primate ancestors of humans came to Africa from Asia. While those primates ended up going extinct in Asia, their lineages diversified in Africa.
Then when the land bridge fully emerged, these primates re-colonized Asia and Europe. This uplift also had significant impacts on ocean circulation and Earth’s climate. Without the Tethys Sea and oceanic currents redistributing energy to the north, the Indian Ocean got warmer and eastern Africa became more arid.
Researchers believe this event was a final trigger in making the Sahara a desert, maybe even driving early hominids out of Africa some 10 to 7 million years ago. The warmer ocean also enhanced evaporation and monsoon activity making southeast Asia wetter and an ideal habitat for the newcomers. The study, " Collision, mantle convection and Tethyan closure in the Eastern Mediterranean ," was published in the journal Nature Reviews Earth & Environment.
Additional material and interviews provided by University of Texas at Austin ..
