The ancestors of African elephants grazed on grasses millions of years before they evolved teeth that could grind the tough, gritty plants, a new analysis finds.
Some 20 million years ago, elephant ancestors inhabited forests and nibbled on leaves with low-crowned, rounded teeth. Roughly 8 million years ago, while grasslands were expanding across East Africa, ancient elephants switched to a grass diet, paleontologist Adrian Lister of the Natural History Museum in London reports June 26 in Nature. Lister computed the timing of the shifts in dining habits and the environment by analyzing the chemistry of fossilized elephant teeth and soils in East Africa.
He also found that elephants didn’t evolve high-crowned teeth with ridges suitable for grinding grass until after 5 million years ago. Lister wonders what could explain the 3-million-year lag between elephants’ behavioral and anatomical changes. Perhaps, he says, the amount of dust and soil grit that make grasses abrasive was too small to force the animals to adapt until after Africa became really arid and dusty a few million years ago.