Mush, Meat and Atkins: Exploring the Evolution of the Human Diet

Early humans living alongside great apes millions of years ago may have gained a competitive evolutionary advantage by embracing a primitive version of the Atkins Diet, according to new research discussed today at the 2005 AAAS Annual Meeting.

But Craig B. Stanford of the University of Southern California hastens to add that our earliest ancestors weren't "buying cartons of eggs from the market," and probably ate many more raw vegetables, fruits and lean meats than today's heavy-protein advocates.

Stanford concedes that studying our ancestors' lifestyles may not provide concrete diet tips for today's weight-conscious humans. But, he said, we may gain fundamental insights to our origins, and thus, our behaviors, by investigating the fossil record.

The results of a nine-year field study of mountain gorillas living with chimps in Uganda offer intriguing new clues to the evolution of the modern human diet, Stanford said. The late Dian Fossey's studies of "gorillas in the mist" may have left many laypeople with the impression that gorillas are docile, cow-like creatures who favor leaves, while meaty foods are left to high-energy chimps. Fossey's gorillas, however, lived in a cold, wet, volcanic region of Africa and had little access to meat, Stanford explained. In more typical environments, he said, gorillas compete aggressively with chimps for available meat sources, and offer useful clues to the dietary adaptations of our early hominid ancestors.

Increased meat consumption triggered genetic changes that allowed early humans to eat more fatty foods without developing heart disease, according to work by Stanford and gerontologist Caleb Finch of USC.

Today, Peter Lucas of George Washington University said at the AAAS Meeting, children with too many crooked teeth in a small jaw may have evolution to thank. Tool use and cooking have reduced food-particle sizes, resulting in facial dwarfing.

Lucas, author of Dental Function Morphology: How Teeth Work, said that food-particle size correlates with the size of a creature's teeth, jaws and body size. The first human ancestor probably learned to cook to spare his little teeth, Lucas said. After all, a cooked potato can reduce stress to molars by up to 82 percent, compared with a raw potato.

Peter S. Ungar of the University of Arkansas also studies dental evidence to understand the evolution of the modern diet. At the AAAS Meeting, he was expected to describe two new methods for analyzing shape and wear patterns on teeth. "Tooth shape reflects diet. Think of carnivorous dinosaurs with their sharp, dagger-like teeth," Ungar explained. "We can infer the diets of fossil primates by comparing the lengths of shearing crests on unworn molars with those of living species with known diets."

Would gorillas and early hominids have approved of the Atkins Diet? Stanford is skeptical, noting that early humans' meat consumption "was limited to game they were able to chase down and kill," whereas modern humans in the developed world "can stock up on nearly limitless amounts of protein."

Renowned paleoanthropologist Bernard Wood of George Washington University, whose lifelong quest to understand our origins included work with the legendary Richard Leakey, said that any sudden, dramatic dietary changes could prove quite challenging for modern humans.

"We've evolved to eat mush!" Wood quipped. "We're a pretty puny bunch, really, with small teeth and small jaws. If we can't get the foods we like, and we have to adapt quickly, we might be in a terrible mess because our teeth and jaws aren't equipped to cope with anything very substantial."

Nonetheless, Stanford said, studying dietary adaptations over time can help us better understand our choices today. "People go to the therapist to understand themselves," he said, repeating a bit of wisdom he often shares with his students in the classroom. "They go into biological anthropology because they want to understand what the human species are all about."

The AAAS session on the evolution of the human diet was organized by Mark Teaford of the Johns Hopkins University.

— Ginger Pinholster

18 February 2005

For more information, listen to Science Update's radio installment, Crowded Teeth.