Amend that popular picture of early man as the fierce, aggressive hunter of animal flesh, dominating his women because he brought home the main food supply.

Amend, too, the picture some women anthropologists have been painting, in reply to what they call that "male chauvinist" anthropologists' fantasy, of largely vegetarian men and women peacefully gathering edible plants in an unbloody dawn of human cooperation.

A group of young anthropologists, men and women, told the American Association for the Advancement of Science yesterday that both of these extreme dietary theories of human evolution are probably wrong.

They said early man and early woman were apparently much like modern man and woman, eating anything they could get, both meat and plants, in significant quantities.

This may be some of the most important new knowledge about early humans and pre-humans in years. Students of anthropology agree that food, and the search for food, played a large role in shaping society and relations between the sexes. And if early humans were mainly meat-eaters, this naturally might have given the males, who "brought home the bacon," a dominant role.

"It is very important, therefore, that we find out what our ancestors really ate," Dr. Glynn Isaac of the University of California at Berkeley said here. "Studies of the evolution of human diet have until recently been fragmented and not very rigorous."

Enter then the new young, unsexist anthropologists.

They have been seeking, impartially, new clues to early diets and what diet has to say about male-female roles. They examine microscopic wear patterns of pre-modern teeth and the shape of prehistoric hominid and earlier primate jaws, shapes that differ with predominant diet.

They analyze these creatures' bones for chemical clues to what they ate, and reread the records of early agriculture and many primitive societies.

"From all we know so far," said Kathleen Gordon of Johns Hopkins University, no Miocene or pre-Pleistocene creature--that is, no pre-human of 25 million to 2 million years ago--was an exclusive or full-time carnivore or meat-eater, and none was a full-time grazer or grain-eater.

"We've looked at animal bones from Tanzania and Kenya, bones 2 1/2 to 3 million years old," said Henry Bunn of the University of California at Berkeley. The bones clearly show hominid butchering or "cut marks." Meat clearly was eaten, "but plant food probably played an important part too."

"We measured strontium in 11,000-year-old human bones from a cave in Israel, in the western Galilee," said Andrew Sillen of the Smithsonian Institution. High strontium content would indicate a plant diet; low strontium, a meat diet. "These bones fell midway," he said.

Other scientists looked at evidence in Africa, Israel, Iran and elsewhere.

The "balanced view" they say they now see is not the view of the main "man-the-hunter" historians, Raymond Dart and the late Robert Ardrey, author of "The Territorial Imperative." Nor is it the view of the two most articulate "plant-diet revisionists," Adrienne Zihlman and Nancy Tanner, author of the recent "On Becoming Human."

"The controversy has been fairly fierce," said Isaac. "We certainly do not yet know the precise composition of early diets. We need a lot more evidence. But the evidence we have leads us to believe neither extreme was the reality."

In short, the prehistoric hunters and gatherers--they were generally both--were usually "omnivorous," in the scientists' phrase. They ate fruits, nuts, wild grains--and meat.