Forget about your Pierre Cardin suit and American Express Gold Card, your Sony Walkman and Reeboks. Down where it counts, you're nothing but a cave dweller and, according to a group of anthropologists, you'll be much better off once you realize this fact. "The Flintstones," it seems, was a better role model than a generation of parents ever suspected.

"When you wake up in the morning and look in the mirror, you see a successful, accomplished, respected member of modern western society," says S. Boyd Eaton. "But inside each of your body cells, your genes are saying, 'No way, baby. We're not 20th century, we're Stone Age.' "

Eaton, a radiologist at West Paces Ferry Hospital in Atlanta, has been taking the prehistoric route for about a decade. His neighbors haven't suspected a thing, probably because he's not wearing animal skins, beating his chest with his fists and yelling "yabba-dabba-do" at the first opportunity.

In fact, Eaton behaves in a pretty ordinary -- if extremely healthful -- fashion. He walks to and from work, a round-trip distance of 1.8 miles. After work, he does an hour of either aerobics (swimming, bicycling) or strength training (weights). The former is good for cutting down on body fat and improving cholesterol distribution, while the latter helps prevent minor and major injuries and osteoporosis.

As for Eaton's meals, he aims to get 60 percent of his calories from carbohydrates, 20 percent from fat, and 20 percent from protein -- but no red meat. ("He's achieved a diet that meets the strictest recommendations made by health groups," comments a spokesman for the American Dietetic Association.) The radiologist consumes about half the fat, a little more protein and somewhat more carbohydrates than the average American.

What he does, however, is not half so interesting as why he does it.

"I tend to order my nutrition in a way that has a plan behind it," says Eaton, 49. "I'm trying to use the materials we have in the 20th century to duplicate the nutritional essentials that our ancestors -- those who lived before the advent of agriculture -- had in their diet." Likewise, he's trying to get prehistoric forms of exercise.

Eaton is collaborating with the husband-and-wife team of physician and Emory University anthropology department chief Melvin Konner and anthropologist Marjorie Shostak on The Paleolithic Prescription, to be published next year by Harper & Row. Basically, these scholars argue, the evolutionary forces that have acted over the past million years are what have determined our present-day bodies. But technological evolution has knocked this equilibrium out of balance.

"The way evolution works is, if the environment changes -- a climatic change, for instance -- it may be that a life form no longer fits that kind of pattern," explains Eaton, who is also an adjunct associate professor of anthropology at Emory.

"Then evolution will work to select those life forms that fit the new environmental circumstances. This is a very long process, but we humans have developed a way of changing our environment so rapidly that genetic changes can no longer keep pace with our cultural changes."

Take the air conditioning in your living room. You're sitting there reading The Brothers Karamazov when the sun starts steaming through the window. As the room heats up, the thermostat kicks on, seeking to lower the temperature to 78 degrees. Soon cool air begins to wash over you.

Your body, a jealous type, isn't thrilled by this. "Hey, I can handle the problem," it says. "Use me!"

"My body could be sweating now to cool me off in the heat here, but it doesn't have to," comments Eaton. "And since those calories that would have done this aren't being used, they're being added to my rear end or my tummy."

Maybe sitting in the unairconditioned sun is too slow a method for keeping excess Ding-Dongs off your waistline. Nevertheless, if you compensate for these and other technology-induced bulges -- if you, in general, live in tune with the biology that evolution has provided you with -- you just might live longer.

Hunter-gatherers, for example, tended not to suffer from obesity, coronary arteriosclerosis or essential hypertension. When Eaton was a medical student, he was told that increases in body fat, blood pressure and serum cholesterol were manifestations of age.

"If your body fat is 15 percent at age 20, by the time you're 50 it could be 30 percent," says Eaton (his own body fat level is 14). "But it's not typical of those living in hunting-gathering societies, and it wasn't typical of our ancestors." Nor does it have to be typical of us.

Of course, the life expectancy of late-paleolithic people (all of whom were hunter-gatherers, and lived from about 40,000 to 20,000 years ago) was only 35 years. In modern society, that's hardly enough time to acquire a six-figure slice of consumer debt, but these three scholars want only to incorporate the best features of our ancestors' lives -- no infectious diseases need apply. Says Eaton: "We could have it all."

Some of The Paleolithic Prescription's other suggestions may be more controversial. These range from more breast-feeding (most American kids are weaned by nine months, but the norm for much of human civilization has been about two years) to the benefits of multi-age play groups (another area where we've gotten away from the historical norm). The Shostak-Konner family is putting many of these precepts into practice.

Shostak, who wrote in 1981 the well-regarded Nisa: The Life and Words of a !Kung Woman (based on 2 1/2 years field experience in northwestern Botswana), sees the paleolithic viewpoint as informing a host of social issues.

"It's a matter of helping people make choices on a solid background of what it has meant to be human for 90 percent of the time people were human on the Earth," she says. "So much of our talk about diet and exercise comes from what we found out yesterday and what we expect to find out tomorrow. It's very shortsighted."

Take sleeping with your baby, the rule throughout much of human history. Many contemporary parents wouldn't want to have their infant in bed with them, due to worries about the child waking up frequently in the night and his influence on mom and dad's sexual relations.

On the other hand, says Shostak, there are "a lot of people who would want to sleep with their babies, but don't know it's an option. We have an 8-month-old, and when I told my physician she was sleeping with us, he told me that was great. But I talked to many women who told me they haven't even thought about it."

Most non-western cultures, she points out, do not put babies in separate rooms from their parents, and clearly parents and young children slept together in hunter-gatherer tribes. "So when people say to us, 'Aren't you afraid you're going to spoil her,' or 'That much human contact is not good,' our attitude is, 'You've got to be kidding. What's the effect of not having that contact?'

"We're not saying it's wrong not to sleep together," says Shostak, 42. "But for those who have the inclination to be indulgent, or want to be physically close to their children, there's a precedent, and a very ancient one. If you know what has gone before, you can find support for doing so many things."