"All natural" diet? there is no such thing.

• Position: Your Life

From the paleolithic to the raw food diet, many health-conscious Americans now want to eat the way they believe our ancient ancestors did, but some of these dietary prescriptions make little sense for modern humans, reveals a book on the evolution of the use of food and eating habits among prehistoric people. While there is much we can learn from what our ancestors ate, many of our more modem foods and diets were developed for very good reasons, indicates Kristen Gremillion, author of Ancestral Appetites: Food in Prehistory.

"Human are omnivores and we can eat a wide range of things. Rather than try to base a healthy diet on what we think people used to eat thousands of years ago, it would probably make more sense to look at our nutritional requirements today and find the best way to meet them."

Gremillion points out that a number of new diet fads claim that they somehow are more "natural" because they locus on a time before modern culture spoiled our eating habits. That time never existed," she insists. "Human dietary behavior can't be reduced just to our biology. Culture has always played a part in what we eat and how we eat it--people always have been innovating, finding new foods to eat and new ways to prepare them. There's no way to say that there's only one way we are supposed to eat."

One popular diet is the so-called "paleo" or...