I was watching a cooking show the other night—“Good Eats” with Alton Brown—that demonstrated why we get more nutrients from cooked vegetables than we do from raw vegetables. While cooking destroys some vitamins, it leaves plenty behind that are more available to our digestive system. Raw vegetables have more vitamins, but our teeth and digestive system can't efficiently digest the plant matter that contains them. Consider how your teeth and jaws have to work to chew a raw carrot. How long would your teeth last if they were stressed that way at every meal? Fruits are softer, but they contain sugars and acids that destroy tooth enamel.

Digesting raw vegetables creates enough excess gas to cause lots of discomfort. Fruits cause even more severe gastrointestinal problems. Grains also must be processed before they serve as the ‘staff of life.’ Without pounding, grinding, dissolving and heating, wheat, corns, rice, most legumes and seeds are virtually indigestible- to humans at least. Cows, birds, and mice can eat grains right off the stalk along with the stalk itself. Although humans require vegetation as a source of nutrients and calories, we did not evolve to eat them raw.

But that doesn’t make us carnivores. That tender steak in the upscale restaurant has been hanging around ‘tenderizing’ for many weeks before it melts like butter in your mouth. Most cuts of meats require marinades, stewing, grinding, or pounding with a mallet before they can be chewed, but chewing is only part of the problem. Eating raw meat of any kind is risky for humans. Unlike predators such as lions or wolves, our digestive systems did not evolve to eat unprocessed meat. Internal organs, such as livers, brains and intestines are protein rich and easy to chew, but we still never eat them raw. I’m not sure why we cook internal organs, but if we prefer to not eat raw innards is it reasonable to assume that we evolved on a such a diet? Try to get a two year old to eat liver, raw or cooked.

Which is another important point. Humans need protein, and lots of it to develop our big brains. Most of this brain growth takes place before age five. Salmonella, E. coli, and other bacteria in raw meat are deadly to infants and toddlers. By age three, children are weaned, but they still need a high protein diet. Something happened long before we were Homo sapiens that enabled toddlers to get enough protein to feed a growing human brain.

We need animal sources of protein. We need vegetables for vitamins. We need to eat what our teeth can’t chew and what our stomachs can’t digest. There are some exceptions.

We can eat raw sea food without much risk. As long as the water isn’t contaminated, and the fish is fresh, sushi is a healthy source of protein. It also is easy to chew and easily digestible. However, our bodies can't manufacture most of the vitamins that are required for good health, so our teeth and digestive systems didn't evolve solely on sole. And we are still left with a vitamin deficiency.

That brings us back to what we do eat, and what people all over the world eat: cooked meat and vegetables. “Taphonomy” is a branch of science that studies what foods a species teeth evolved to eat based on the types of teeth the species has. Cats and dogs have teeth suitable for ripping flesh. Cows and horses have blunt teeth that suitable for eating plants. Great apes have teeth that grind vegetation. Human teeth cannot rip flesh nor sufficiently grind plants to release nutrients. Our teeth are smaller than other apes but our teeth work very nicely if vegetables, grains, and meat have been cooked.

Until recently I believed, like most non-anthropologists, that hominids tamed fire after we evolved our bigger brains. However, according to “The Tree of Origin” there was evidence of fire control 300,000 to 400,000 years ago. Hominids smaller teeth appeared 250,000 years ago. The authors suggested there are strong signals that cooking originated more than 1.6 million years ago. Another source, “The Demonic Male” by Richard Wrangham & Dale Peterson (1996) cites the same theory.

Australopithecus, lived about 2 million years ago. They didn't have much of a bigger brain than modern gorillas, but they were smart enough to use cutting tools to scrape meat from bones. These woodland apes also had smaller mouth and teeth than chimpanzees do. We will never know if they used fire to sanitize, tenderize and preserve food. Our modern teeth and digestive system suggest that they did.

It is possible, and even very likely, that use of fire to alter food played an important part in our evolution. Unlike other animals, we are mesmerized by fire rather than terrified of it. Cooking food removes hazards of bacteria and parasites, allows us to exploit food sources that we otherwise couldn't use, and even begins the digestive process for us. Did our hominid ancestors move down from the tree tops to walk or to cook? The idea at least is something to chew on the next time you sit around a campfire.

Nancy Sherer