CHICAGO (AP) - Richard Wrangham has tasted just about everything that chimpanzees eat in Africa and once considered seeing if he could live on that diet.
"I realized I'd be pretty hungry," Wrangham reported. "It would be difficult for a human to survive on a chimpanzee's diet."
The signature of the human diet is cooking, he said Thursday at a meeting of the American Association for the Advancement of Science.
By changing the forms of starches, fats and proteins, cooking concentrates the nutrients in foods, he told a panel discussing the dietary habits of early humans.
Lined up along the table was a series of ancient skulls, exhibits of the wear and tear of early foods, smiling eerily at the audience.
What our earliest ancestors ate has long been a subject speculation among anthropologists like Wrangham, of Harvard University. More and more evidence is offering clues to their diet.
"The hallmark of the human diet is flexibility, the ability to find or make a meal in any environment," said anthropologist William Leonard of Northwestern University.
High nutrition diets became necessary for humans to meet the increasing energy demands of the large brain, and the hunting-gathering lifestyle developed as humans took advantage of grazing animals such as antelope and gazelle.
The staple foods of humans are much more nutritionally dense than those of other large primates, which can subsist on leaves and fruit, he said.
The size and shape of the jaw and wear on the teeth can tell us a lot about what ancient people ate, said Peter Ungar of the University of Arkansas.
Yet it can sometimes be misleading.
For example one skull with large, flat teeth was thought to indicate a diet heavy in nuts that could be chomped open. But tooth wear and other evidence indicates that this individual mostly ate softer items for an everyday diet.
"Maybe what we are looking at (in the teeth) is a fallback adaptation for when the preferred foods weren't available," he suggested.
Matthew Sponheimer of the University of Colorado noted that "mechanically challenging" foods such as nuts were only available at limited times of year,
His chemical tests indicated a varied diet 2.5 million years ago including sedges, grasses, seeds and perhaps animals.
Evidence for a variety of diet in different places was cited by Leonard, who noted that animal herders in Siberia get more than half of their food from meat, while meat makes up only 5 percent to 6 percent of the diet of potato farmers in Peru.
The modern western diet - blamed for the rapid growth of obesity - has minimized the effort needed to provide high-quality food, he said.
There has been a rash of people offering diets touted as similar to those of early humans, commented Sponheimer. If people are going to do that they "have an obligation to get it bloody right," he said.
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