(CN) --- An ever-changing climate and brutal ice ages over the course of millions of years put early elephant species on the defensive and allowed only the most adaptive pachyderms to survive, according to a new study released Thursday.
While the world of today is home to just three species of endangered elephants hailing from Africa and Asia, a few hundred thousand years ago Earth enjoyed the company of countless varieties of the lumbering beasts. From straight-tusked elephants to the famed giant mammoths, elephants of all shapes and sizes once roamed the early Earth before so many of their kind ultimately fell to extinction over countless centuries.
Previous research into the fall of the order Proboscidea, the group all living elephants fall under today, laid much of the fault on over-eager early humans who brought the big game to near extinction. Not unlike what happened with the American bison in the 1800s, researchers have long believed that early humans saw elephants as a reliable source for food and hunted them with reckless abandon.
Today, new research suggests that while humans may have played a role in the decimation of elephants, a much larger culprit may be more to blame: a drastically unstable early climate.
In a study published in Nature Ecology & Evolution, an international group of paleontologists reveal that they believe the fall of elephants did not stem from aggressive early human hunters, but rather was driven by over a million years’ worth of changing climates and habitats that afforded pachyderms very little room for error.
Experts say this downfall can be traced back to around 20 million years ago when, back when continents as we know them today were still forming, the Afro-Arabian plate crashed into Eurasia. While elephants up to that point were slowly-evolving creatures, the collision of these two landmasses opened up all new land for ancient elephants to explore.
This expansion resulted in a surge of elephant evolution at a rapid pace, but they perhaps were evolving too fast for their own good. The climate of Earth at the time was in near-constant flux, and as elephants evolved quickly, numerous diverse species found themselves living together in niche habitats --- habitats that simply wouldn’t stop changing as the years dragged on.
Zhang Hanwen, study coauthor and honorary research associate at the University of Bristol's School of Earth Sciences in the U.K., said this resulted in an environment that essentially left elephants with a single choice: adapt to the ever-shifting landscape or be left behind.
"The aim of the game in this boom period of proboscidean evolution was 'adapt or die',” Zhang said. “Habitat perturbations were relentless, pertained to the ever-changing global climate, continuously promoting new adaptive solutions while proboscideans that didn't keep up were literally, left for dead.”
This race to survive through adaptation carried on for a few more million years until around three million years ago, elephants from Africa and eastern Asia seemed to emerge as the dominant pachyderms.
But Mother Nature wasn’t done just yet. Shortly after certain species of elephants appeared to have stood the test of time, a series of harsh ice ages hammered elephant populations across the world. This once more forced elephant species to adapt and survive, this time with elephants armed with strong tusks built for digging up vegetation and thick outer hides --- not unlike many of the surviving elephants today --- being favored.
While several elephant species were able to make it out of the ice ages, the damage was already done and countless types of elephants failed to pass muster before the judgment of Earth’s early, fickle climate.
This is not to suggest, according to researchers, that humans certainly didn’t play a role in spurring on the downfall of elephants. Experts believe that once humans arrived on the scene in force, the surviving elephants, already brought to the brink by nature and stretched thin, stood no chance against the emerging humans and their quest to become Earth’s apex predator.
“In our scenario, modern humans settled on each landmass after proboscidean extinction risk had already escalated,” Zhang said. “An ingenious, highly adaptable social predator like our species could be the perfect black swan occurrence to deliver the coup de grâce."
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