In his April 1 column, Marc Fried said that for most of our evolutionary history humans — or hominids, more precisely — had been frugivorous, subsisting on raw fruits and other vegetable foods.

Well, he's probably right about the frugivorous point, but not the raw one. Richard Wrangham, in his new book Catching Fire: How Cooking Made Us Human (Basic Books 2009) locates the shift from the earliest hominid species, such as Homo Habilis, to the more successful Homo Erectus as stemming from mastery of fire which allowed the cooking of tough tubers and other wild foods of East Africa around 1.9 million years ago.

Wrangham, a professor of anthropology at Harvard and author of several books, has for decades studied chimpanzees. He notes that chimps spend five or six hours a day simply chewing. To get enough calories from wild foods, one would need to forage and eat all day long. Consider how long it would take to chew a raw sweet potato. Cook it and it's off your plate in five minutes or less. Beyond that, tubers and other tough, fibrous, wild vegetables are easier to digest when softened by cooking.

There are thus two hugely important shifts during this early period of Hominid evolution. The first was from the Australopithecine Apes — "Lucy" and several other species, including the newly described A. Sediba — to the very first Hominid species, such as Homo Habilis and Homo Ergaster. Wrangham suggests that this change may be due to eating more meat. That means raw, uncooked meat scavenged off lion and hyena kills. Wrangham also explains that wild zebra and antelope meat is closer to a leather belt than a factory farm steak, so these early Hominids gained some valuable energy from this increased meat intake, but they still spent a long time chewing it.

Interestingly enough, research into human tapeworms seems to corroborate this idea. The human tapeworms are closely related to those that infest lions and hyenas. This indicates that our ancestors ate some of the same kind of meat that lions and hyenas ate. However, to imagine four foot tall Homo Habilis, with his short legs, actually hunting zebra and antelope is a bit of a stretch. Scavenging kills would have been far more productive.

Wrangham says that the jump from Homo Habilis to Homo Erectus is marked by a set of significant changes. Erectus's teeth are smaller, as are the jaws, while the brain and the body overall are much larger. We went from little critters four-feet tall, with huge teeth and long arms, to recognizable people, five and a half feet tall, with brain sizes much closer to those of modern humans. The other thing that changed was our digestive systems, which shrank dramatically.

Homo Erectus had therefore gained a fairly dramatic boost in energy input. The use of fire, primarily to heat and soften the tough vegetable foods of East Africa, is an obvious route to such gains. And, no doubt, along the way, Erectus learned to roast the meat scavenged off lion kills. That would have cut down the parasite load as well as making the stuff easier to chew.

None of this is to say that Fried is wrong about raw food. Raw foods come with all their vitamins and enzymes intact. It's just that today, instead of employing massive molars, we now have appliances, such as blenders and juicers, do the heavy lifting. All we have to do press a button.