The impression that prehistoric man was a macho hunter who returned to his cave at the end of the day with a load of mastodon meat is all wrong, according to Dr. Vaughn M. Bryant, head of the anthropology department at Texas A&M University.
Picture a group of 20 or 30 individuals ambling across the tall, grassy plains of East Africa, snacking on tough grass, seeds, roots, berries, and nuts as they walk along, and you have a more likely image of food-gathering 5 million years ago.
The meat part of this diet was probably limited to field mice, lizards, fish, birds, and small insects, Dr. Bryant explained, speaking at a program sponsored by the California Avocado Commission at the Newspaper Food Editors Annual Conference here.
''Our ancestors on the plains of East Africa must have been snackers. Their meals were certainly nothing like ours,'' he says.
''After all, the more they ate while searching for food, the less they had to carry. So there was no need for the group to gather at specific times each day to eat large meals.
''Food was based on trial and error until they learned which plant foods were good to eat and which were not. Plants were dominant in the diet. Meat was a luxury.''
Because these people lacked an understanding of fire, food was eaten raw and may have been tough to chew, Dr. Bryant explains, adding that the food was high in fiber - but all natural, of course.
Fire was an important step regarding food as early as 750,000 years ago, in an era of open campsites and cave living.
''The people obviously liked the taste of cooked food, and it helped expand their menu,'' Dr. Bryant notes. ''They were also eating more meat, thus establishing an omnivorous diet pattern, which brought other advantages.
''Since meat has a holding power, it allows a person to go for longer periods of time without food.
''Higher ratios of meat meant that eating time could be reduced and chewing was easier,'' he says. ''Also, with fire, it was possible to smoke meat to preserve it for long journeys.''
Dr. Bryant tells also of the domestication of plants and animals, which began when people abandoned their nomadic life styles, causing another major change in diet, about 10,000 years ago.
Domestication meant a reliable, but often monotonous menu of a few cultivated foods and meat that contained more fat than the undomesticated.
Dr. Bryant, a colorful speaker, takes his role as teacher and researcher seriously. ''I believe we all need a smattering of psychology and a smattering of sociology plus some history and all the liberal arts in our education,'' he says.
His studies are based on his research of ancient human diets from material found in caves located in France and Africa.
He has also researched prehistoric human diets in Peru and in the state of Kentucky. His three-year study for the National Park Service in Arizona resulted in a better understanding of the food and agriculture of the ancient Pueblo Indians.
''I'm not suggesting we abandon today's life style and go back to living in caves,'' he says, although he has come close to caveman living himself.
In the summer of 1974 he took students to an archaeological dig in southwest Texas near the Mexican border, where there are still abundant supplies of wild foods that prehistoric people ate.
The group foraged for food at 6 o'clock every morning and found cactus, which made up 60 percent of their diet, as well as wild onions, nuts, berries, and agave, a plant similar to yucca. They also ate fish and rattlesnake.
Dr. Bryant doesn't always eat this kind of food. ''I'll never say a primitive diet will ever taste as good as pizza. But we can learn something here,'' he says. ''Prehistoric man ate lean meat, fish, and fowl. The caveman lacked refined sugar and salt was scarce. They got lots of exercise daily.'' Bryant has for the past seven years been foraging in the supermarkets rather than in the wilds.
''We were designed to be hunters and gatherers,'' he says, ''but technology has moved faster than our own physiology. Caveman foods may not be for everyone, '' he admits, adding that he is neither a nutritionist nor a fanatic.
''I like modern amenities like air conditioning, football games on television , and hot baths, but we can have the best of both worlds.''