Human ancestors radically changed their diet 3.5 million years ago, adding more grasses and meats, according to new research.
By studying the teeth of hominins, ancestors to humans, researchers were able to determine that the creatures moved from a chimp-like forest diet to one more like our modern diet at that time, known as the middle Pliocene Epoch.
Before the switchover, the forest-derived diet of hominins largely consisted of fruit, herbs, leaves, and shrubs, similar to the staple foods of chimpanzees.
Researchers studied the ratio of carbon isotopes in the enamel of teeth from 175 members of 11 hominin species, baboons, and other primates from East Africa. The animals studied lived there between 1.4 to 4.1 million years ago.
"What we have is chemical information on what our ancestors ate, which in simpler terms is like a piece of food item stuck between their teeth and preserved for millions of years," Zeresenay Alemseged, of the California Academy of Sciences, said.
They found that two of these species, Australopithecus afarensis and Kenyanthropus platyops, began to eat more grasses and sedges (which are much like grasses). These species also began to hunt in the open savannah more often and consume meat in far greater quantities 3.5 million years ago than their predecessors. No such dietary change was found in non-hominin species.
Researchers believe that when hominins started moving away from woodlands and into the savannah, they began eating the local fare, which included grasses and animals. Savannahs became more numerous during a period ending six million years ago. By four million years in the past, during the middle Pliocene Epoch, our ancestors developed a more complex brain, stood upright and ventured into the savannah.
"For a long time, primates stuck by the old restaurants - leaves and fruits - and by 3.5 million years ago, they started exploring new diet possibilities - tropical grasses and sedges - that grazing animals discovered a long time before, about 10 million years ago when African savanna began expanding," Thur Cerling, principal author of two of the four studies announcing the findings, said.
Because this new diet would have relieved chimpanzees and other large primates from competition for food, these new findings also help explain how several varieties of large primates which existed at that time and place could co-exist together, a question which has long puzzled paleontologists.
The four studies developing the new research were published in the journal Proceedings of the National Academy of Sciences.
