The giraffes, pigs, and rhinos that romp in Africa today can trace their roots to the northern climes of Europe. They took over Africa when the continents collided 24 million years ago. But new fossil evidence suggests that an odd assortment of African animals survived the invasion and lingered for millions of years longer than previously thought. The find includes five elephant ancestors that were previously unknown.
Thirty-two million years ago, Africa flourished with strange mammals including an odd rhinoceros-like creature with a huge V-shaped horn. Eight million years later, as the Oligocene era gave way to the Miocene age, the Eurasian continent smashed into Africa, and European mammals spread across the African continent. But a void in the fossil record between 32 million and 24 million years ago left researchers guessing at the fate that befell Africa's native mammals. One guess was that they had all died off before the Eurasian mammals immigrated.
Not so, according to a report in the 4 December issue of Nature. While prospecting in Ethiopia, John Kappelman of the University of Texas, Austin, William Sanders of the University of Michigan, Ann Arbor, and colleagues happened upon a trove of mammalian fossils with distinctly African characteristics. The rocks dated back 27 million years, indicating that African mammals flourished at least up to this point and probably still existed when the European mammals invaded. The discovery of five new species of elephant ancestors, which looked like a cross between an elephant and a pig and stood just over a meter tall, hints at how two elephant species survived when so many other African mammals died off. "If you have a lot of diversity in the group," says Sanders, "you have more niches that you can get into."
The work "documents the story of the winners and losers in Africa," says Ellen Miller of Wake Forest University in Winston-Salem, North Carolina. She says the dig shows that unlike animals such as the V-horned pseudo-rhino, which didn't survive the takeover by northern migrants, "elephants are an incredible African success story." She adds that Kappelman's group is just starting to scratch the surface of the site.