The animals' switch to grasses began after warm-season grasses first appeared in East Africa, but long before grasslands began to spread rapidly in the region. Previous evidence indicates East Africa was dominated by C3 ecosystems (trees, shrubs and cool-season grasses) during the Middle and Late Miocene Epoch about 16 million to 5 million years ago, but that mosaic landscapes with C4 grasslands were present.
Cerling's previous research found no evidence of widespread grasslands earlier than 4.2 million years ago. "A major shift toward arid environments in the region began about 2.7 million years ago," Uno says. "And only during the past 1 million years did grasslands become as dominant as they are today in East Africa."
But even before 4.2 million years ago, "there was enough C4 grass around for a whole bunch of animals to make a living off of it," he adds.
The first herbivores to eat C4 grasses had longer teeth that took more time for abrasive grasses to wear down. The increased availability of C4 grasses meant there was a new food source available for any herbivore to try if they could digest the gritty grasses, which have more cellulose and lower nutritional quality than most C3 plants.
"If you lived in a town that only ate beef for dinner and the frozen fish stick guy came through selling TV dinners at half price (because everyone ate beef), wouldn't you at least try fish for dinner?" Uno asks. "That example is a bit anthropomorphized, but I see C4 grasses as new resources that may not have been as much in demand as C3 cool-season grasses, trees and shrubs. This could be because some animals had a hard time digesting C4 grasses."
A History of East African Plant Eating
The new study showed this dietary history for East Afri
|Contact: Lee Siegel|
University of Utah