On a lunch break at ''The Mind of the Chimpanzee'' symposium in March, Jane Goodall walked with me to visit the ape house at the Lincoln Park Zoo. She let out the chimpanzee pant-hoot call to signal our departure.
Talk about an authoritative guide. Doctor Jane, as colleagues call her, is the most celebrated primatologist of her generation. So this was something like being with a Leakey looking at a hominid skull in East Africa, with Neil Armstrong inside an Apollo spacecraft or with Stan Musial at the World Series.
Jane Goodall, then a young English woman without experience or a college degree, arrived in Africa nearly a half-century ago to observe and write about animals. Encouraged by Louis Leakey, a pioneering paleoanthropologist, she set up the Gombe field station in what is now Tanzania. Almost from the start, in 1960, she brought to science and the public a new understanding of the behavior and culture of chimpanzees.
At an outdoor enclosure next to the ape house, Dr. Goodall took in the scene of chimpanzees large and small lazing about, scratching themselves, munching on something or cavorting on tree limbs and along ropes simulating vines.
''There's the alpha male,'' she said, immediately sizing up the cast of characters.
A zoo official said the alpha was a 16-year-old named Hank. He was stretched out like an overfed potentate, relaxing at the base of a tree from his duties as a propagator of the species. Not far away on a tree branch, a 7-year-old male named Kipper kept a worshipful eye on Hank, his role model.
''Young males pick out an older male -- it doesn't have to be the alpha -- and follow him around and study everything he does or doesn't do,'' Dr. Goodall explained. ''It's part of their separation from Mom.''
Dr. Goodall described her earliest experiences observing such social traits in the wild. At first, the Gombe chimps fled whenever she appeared.
''You can imagine what it was like for the chimpanzees,'' she said. ''They had never seen a white ape before.''
She settled for watching the animals from a distance with binoculars. She said she always wore the same clothes and kept to the same routine, never making an approach that might seem threatening. After a few months, her patience was rewarded. An older male, whom she named David Greybeard, ventured toward her.
''I held out a banana, and he kept getting closer and closer,'' she said. ''He was my link to the others, getting me through the door to their world.''
Soon, Dr. Goodall saw David Greybeard and other chimps breaking and modifying sticks for ''fishing'' termites and ants from their nests. Humans, it seemed, were not the only toolmakers. She also observed chimps going off on hunting trips, revealing that they were not totally vegetarians and fruit eaters. She also discovered their violent sides.
''Chimpanzees are like us in so many ways,'' Dr. Goodall said.
She is now 73, her blond hair turned gray, though she still ties it in the back as she did in her Gombe years. She is slender and smiles a lot with her eyes, recognizably the woman in the old pictures, the one standing in deepest Africa with a chimp at her feet, reaching up to lift the tail of her khaki shirt.
A chimp named Fifi was the last survivor of her original group of subjects at the field station. Chimps often live 40 to 50 years in the wild, longer in captivity. ''Two years ago, I lost my old friend,'' Dr. Goodall said of Fifi.
A young chimp at the zoo ascended to the highest limbs of a tree to show off his acrobatic skills. Several others took their noontime ease along a ledge, one good-size male flashing a wide grin as if rehearsing monkeyshines for a television commercial. No, Dr. Goodall corrected, this was just the facial expression of a chimp eating.
A high-status female, probably the alpha's favorite mate, stirred from a nap. Elsewhere, two females frisked about, and the reason for their liveliness was apparent. The pink swellings on their rumps announced their readiness to mate.
Dr. Goodall gave up fieldwork years ago. She heads the Jane Goodall Institute and spends at least 300 days a year traveling worldwide as an advocate of conservation in general and the protection of the dwindling numbers of chimps.
The crowd at the zoo began pressing in. It was Saturday, and fathers and mothers had brought their children to the zoo. One mother recognized Dr. Goodall and came forward.
''Oh, I admire you so much, all that you've done,'' the woman said.
She pulled in her husband to meet Dr. Goodall, who gave a gracious smile and thanked them for their interest in her work. Primate communication being what it is, others gathered around. Only the children kept their places at the fence and their eyes on the chimpanzees.
I relinquished Doctor Jane to her admiring public. I went back to the symposium to hear more of what scientists have been learning about chimpanzees since the young English lady and David Greybeard and Fifi got to know one another in Africa in the 1960s, and thus revolutionized primatology.
Photo: NEW MISSION -- Jane Goodall spends 300 days a year traveling to promote conservation. (Photo by Peter Wynn Thompson for The New York Times)