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The dynamic processes occurring deep within the Earth’s crust, while seemingly distant, have far-reaching consequences that shape our planet’s geography and influence climate systems, ocean currents, and even the evolution of species. A recent study suggests that a significant mantle plume might have played a crucial role in the evolution of early human ancestors by facilitating the formation of a land bridge between continents.
In a recent publication in Nature Reviews Earth & Environment, a collaborative team of international researchers delves into the geological events that led to the emergence of this land bridge approximately 20 million years ago, which connected Asia and Africa via what is now the Arabian Peninsula and Anatolia.
This research synthesizes existing studies and introduces innovative models developed at The University of Texas at Austin’s Jackson School of Geosciences and the GFZ Helmholtz Centre for Geosciences.
The elevation of this landmass allowed for the movement of early ancestors of various species, including modern-day giraffes, elephants, and humans, across continents. This event marked the end of a prolonged separation of Africa from the rest of the world that lasted around 75 million years.
“This research addresses fundamental questions about planetary evolution and the interplay between tectonic activity and life,” remarked Thorsten Becker, a co-author of the study and a professor in the Department of Earth and Planetary Sciences at the Jackson School.
The narrative begins 50 to 60 million years ago, when a tectonic plate began to descend into the Earth’s mantle, creating a “conveyor belt” that enabled superheated rocks to rise and ultimately reach the surface around 30 million years later. This convective activity, along with tectonic plate collisions, facilitated land uplift and played a pivotal role in the closing of the ancient Tethys Sea, thereby forming connections between what are now known as the Mediterranean and Arabian Seas and creating a land link between Africa and Asia.
Eivind Straume, the lead author of the study, conducted an extensive analysis of the geological changes during his time as a postdoctoral fellow at the Jackson School. He highlighted that the formation of the land bridge and subsequent animal evolution were intricately linked.
“The shallow seaway’s closure occurred several million years earlier than it might have due to these geodynamic processes, such as mantle convection and corresponding shifts in the Earth’s surface,” Straume explained, currently a postdoc at NORCE Norwegian Research Centre and The Bjerknes Centre for Climate Research. “Without the influence of the mantle plume, the collision of the continents may have unfolded differently.”
Timing played a critical role; had the connection of Africa and Asia been delayed by even a million years, the evolutionary pathways of the animals migrating between the two regions might have diverged significantly, including those of our human ancestors.
Before the complete closure of the land bridge, primate ancestors from Asia migrated to Africa. Although these primates eventually became extinct in Asia, they thrived in Africa, subsequently re-colonizing Asia following the land bridge’s formation.
“This serves as an example of how long-term geological processes directly inform the evolution of life on Earth,” Straume remarked.
The uplift phenomenon that shaped the Arabian Peninsula also profoundly affected ocean circulation and Earth’s climate systems. Increased ocean temperatures led to more pronounced seasonal temperature fluctuations, contributing to a drier climate in regions from North Africa to Central Asia and paving the way for the Sahara’s transformation into a desert. Moreover, these topographical shifts intensified monsoon patterns in Asia, resulting in increased precipitation in Southeast Asia.
This study integrates diverse fields, including plate tectonics, mantle convection, topographic changes, paleogeography, evolutionary anthropology, and climate dynamics, weaving a comprehensive narrative of the broad impacts of mantle processes throughout Earth’s history.
“We see this as a thought-provoking synthesis of current scientific advancements,” Becker stated.
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