Activity in Earth's mantle created a land bridge that animals traversed
The land beneath our feet holds secrets that stretch back millions of years. Deep within Earth’s mantle, shifting rock and molten heat have nudged continents, created barriers, and shaped migration paths for creatures across the planet.
The link between these buried processes and species of ancient wanderers has captured the attention of researchers.
Among them is Thorsten Becker, a professor at The University of Texas at Austin, who has helped piece together new insights about the deeper forces that affected how species were able to spread.
Mantle forces reshaped continents
Earth’s mantle churns with slow but significant motion that can alter the planet’s surface. Gradual sinking of cooler rock and rising of hotter material create a convection system that fuels changes in crustal elevation and shapes coastlines.
Scientists have found that a towering plume of heated rock may have reached the surface around 30 million years after it began brewing in the depths.
By 20 million years ago, the upward push on land in what is now the Arabian Peninsula had reorganized seas and formed a passage between Africa and Asia.
Mantle uplift created a land bridge
This arc of dry ground broke a 75-million-year pattern of isolation for the African continent. Animals such as elephants, giraffes, and cheetahs made use of the open route, traversing miles of emerging terrain to explore and settle new environments.
“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,” said Eivind Straume, who is now a postdoctoral fellow at NORCE Norwegian Research Centre and The Bjerknes Centre for Climate Research.
Once mantle uplift had created the land bridge, entire groups of mammals made journeys that altered the genetic paths of today’s species.
Impact on human ancestors
Long before modern times, primates roamed Asia. A branch of these primates moved into Africa before returning when the land bridge fully emerged. That dual migration shaped the fate of the lineages that survived and evolved in later epochs.
“It’s an example of how the long-term convective evolution of the planet talks to the evolution of life,” said Straume. Many researchers believe this timing allowed certain primates in Africa to flourish while their relatives died out elsewhere.
Mantle shifts altered Earth’s climate patterns
Closure of the Tethys Sea transformed ocean currents and sparked broader shifts in temperature patterns.
The disappearance of marine passageways altered how water circulated between the Atlantic and Indo-Pacific, changing conditions across northern Africa and central Asia.
Warming ocean waters also set the stage for more significant seasonal temperature swings. Some studies have linked these shifts to intensified monsoon patterns that brought heavier rains to parts of Asia while promoting dryness in the Sahara.
Earth’s mantle uplift and the Sahara
As landmasses rose and air circulation patterns evolved, the Sahara grew drier. The shift from lush zones to desert terrain introduced a new barrier to animal movement. This drying also encouraged adaptation and migration in species seeking water sources or cooler climes.
Over time, the Sahara came to dominate much of north Africa. The new upland surfaces of Arabia, shaped by rising rock, channeled wind and moisture patterns away from former coastal areas.
New perspectives from geological models
Scientists are working with advanced simulations to connect deep Earth processes to events at the surface. These models help illustrate how flows of hot rock influence crustal uplift and seafloor changes. They also provide details on how ocean basins, deserts, and mountain ranges evolved.
“This study has relevance to the question of ‘How did our planet change, in general? What are the connections between life and tectonics?’” noted Becker.
By stitching together multiple lines of evidence, teams can outline how events far below the surface have rippled through layers of geological and biological history.
Animal routes and biodiversity
Large mammals that migrated between continents not only diversified their habitats but also interacted in ways that drove evolutionary shifts.
Elephants, for instance, faced new landscapes and climates that challenged them to adapt. Giraffes and rhinoceroses found novel feeding grounds and survived despite new predators and competition.
Such exchanges left imprints on the genetic makeup of today’s mammal populations. Species that once had limited ranges across Africa or Asia soon encountered new ecosystems.
Lasting consequences for life
The land bridge created by mantle-driven uplift gave early primates and other animals opportunities to branch out. Over millions of years, these varied lineages left evidence in fossils and modern DNA.
Researchers continue to uncover how changing geography shaped not just migrations but also the survival strategies of multiple species.
Those pathways often ran in tandem with major climatic shifts. The interplay of plate collisions, mantle upwelling, and fluctuating sea levels set the stage for both expansions and extinctions.
Further exploration of hidden dynamics
Cutting-edge technology, from seismic imaging to deep-sea drilling, supports the study of how hidden geological processes link to surface environments.
By incorporating detailed uplift models into paleoclimate reconstructions, geoscientists can refine their understanding of ocean currents and rainfall patterns.
With each new discovery, puzzle pieces fall into place. The uplift that once closed ancient seaways still influences today’s wind and precipitation cycles, reminding us that Earth’s lower layers remain busy behind the scenes.
The study was published in the journal Nature Reviews Earth & Environment.
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