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May 25, 2019

Climate change — not humans — wiped out ancient mammals in Africa, according to new study

November 24, 2018
Baby elephants eat at the David Sheldrick Elephant & Rhino Orphanage at Nairobi National Park in Nairobi, Kenya, Elephants are among the last megaherbivores still in existence. (Carolyn Kaster / AP)

Climate change prompted the extinction of many of the large mammals that once roamed Africa, according to a study that strikes down the long-believed view that the earliest humans hunted them out of existence.

In new research published in the journal Science on Friday, scientists analyzed more than 100 fossils and data on megaherbivore communities in Africa dating back seven million years. In that time frame, 28 lineages of megaherbivores — or species that weigh over 2,000 lbs. — went extinct, according to lead author Tyler Faith, an assistant professor in Department of Anthropology at the University of Utah.

Only five megaherbivore species still exist today — elephants, hippopotamuses, giraffes and black and white rhinoceroses. The mammal decline has long been blamed on “our earliest tool-bearing ancestors,” but researchers have concluded those populations began to shrink long before humans appeared.

The extinction process kicked off about 4.6 million years ago, more than a million years before the earliest evidence of humans — like tools for example — appeared.

“Looking at all potential drivers of the megaherbivore decline, our analyses suggest that changing climate and environmental factors played the key role in Africa’s past extinctions,” Faith said in a statement.

John Rowan, a postdoctoral scientist from the University of Massachusetts Amherst noted the “key factor” appears to be the expansion of grasslands, which is likely related to a global drop in atmospheric CO2 (carbon dioxide) over the last five million years.”

As a result, savannas became “less woody and more open through time,” robbing many megaherbivore communities of their food source.


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