WHEN SHE SAILED from San Francisco to Samoa in the summer of 1925, Margaret Mead - then only 23 years old - had little idea that she was embarking on another kind of voyage: a lifelong field trip into the behavior patterns of both distant cultures and her own. An anthropoligist, she would eventually say, has to be an observer and recorder of "everything that happens." It is done by "immersing oneself in life" but being "careful not to drown."

From that first embracing of a remote Polynesian culture until her death this week in New York, Margaret Mead was an American fixture. She was a regular visitor to Washington, and however odd our local tribal customs may have appeared, she was ever a soft touch for anyone who wanted her to testify before a congressional committee, appear on television, talk to student assemblies or merely gab for a few minutes in a cab ride to the airport. Her wisdom was portable.

In the 1920s, anothropological field work often mean little more than a game researcher of two nosing around a primitive village and then going home to write it up like a travelogue. Margaret Mead avoided that kind of intellectual laziness. The scholarship, as well as the fascination, of her books was in her willingness to leave her preconceptions at home. Participation in village life, she wrote in "Letters From the Field 1925-1975," has involved entering into many fcets of the life of the people I have worked among - eating the food, learning to weave a mat or make a gesture of respect or prepare an offering or recite a charm as they had been taught to do, using the disciplined awareness of how I myself felt in the circumstances as one further way of coming to understand the people who were my teachers as well as the subjects of my study."

As avidly as she sought the hard answers in foreign cultures, Margaret Mead had no use for the easy answers at home. She was an independent feminist who believed that "to argue for a woman's right to abortion is absurd. Women have a right to institutions which will see to it that they never have an unwanted child." She had her share of gloom about modern life - America "is in a pit of deterioration" - but she bursted with optimism that our values can be re-ordered.

For a person who went into her prime at an early age and never left it, it was hardly surprising that any number of diverse groups claimed Margaret Mead as her own. For the scientific community, her tireless work at the American Museum of Natural History becaem a resource that could never be exhausted. For young anthropologists, a visit to the Mead office at the museum was a memorable field trip in itself. For the media, she was natural copy - spunky ideas, plain language and a restless pushing on to fresh territories. For the collectors of her books, she had a spacious mind that nudged the reader to broaden his own visions.

If Margaret Mead became known as the grandmother to the world, she stunningly refused to slow down into the reposeful world of grandmothers. But neither did she deny her age. In "Blackberry Winter," the account of her early years, she tells of young people saying that "you belong to us." No, she would reply. "I cannot ever belong to your generation, as you cannot ever belong to mine. But I can try to explain."

That, for more than 50 intense years, is what she did: explain herself to us and explain us all to each other.