Jane Goodall, the trailblazing naturalist whose intimate observations of chimpanzees in the African wild produced powerful insights that transformed basic conceptions of humankind, has died. She was 91.

A tireless advocate of preserving chimpanzees’ natural habitat, Goodall died on Wednesday morning in California of natural causes, the Jane Goodall Institute announced on its Instagram page.

“Dr. Goodall’s discoveries as an ethologist revolutionized science,” the Jane Goodall Institute said in a statement.

A protege of anthropologist Louis S.B. Leakey, Goodall made history in 1960 when she discovered that chimpanzees, humankind’s closest living relatives, made and used tools, characteristics that scientists had long thought were exclusive to humans.

She also found that chimps hunted prey, ate meat, and were capable of a range of emotions and behaviors similar to those of humans, including filial love, grief and violence bordering on warfare.

In the course of establishing one of the world’s longest-running studies of wild animal behavior at what is now Tanzania’s Gombe Stream National Park, she gave her chimp subjects names instead of numbers, a practice that raised eyebrows in the male-dominated field of primate studies in the 1960s. But within a decade, the trim British scientist with the tidy ponytail was a National Geographic heroine, whose books and films educated a worldwide audience with stories of the apes she called David Graybeard, Mr. McGregor, Gilka and Flo.

“When we read about a woman who gives funny names to chimpanzees and then follows them into the bush, meticulously recording their every grunt and groom, we are reluctant to admit such activity into the big leagues,” the late biologist Stephen Jay Gould wrote of the scientific world’s initial reaction to Goodall.

But Goodall overcame her critics and produced work that Gould later characterized as “one of the Western world’s great scientific achievements.”

Tenacious and keenly observant, Goodall paved the way for other women in primatology, including the late gorilla researcher Dian Fossey and orangutan expert Birutė Galdikas. She was honored in 1995 with the National Geographic Society’s Hubbard Medal, which then had been bestowed only 31 times in the previous 90 years to such eminent figures as North Pole explorer Robert E. Peary and aviator Charles Lindbergh.

In her 80s she continued to travel 300 days a year to speak to schoolchildren and others about the need to fight deforestation, preserve chimpanzees’ natural habitat and promote sustainable development in Africa. She was in California as part of her speaking tour in the U.S. at the time of her death.

Goodall was born April 3, 1934, in London and grew up in the English coastal town of Bournemouth. The daughter of a businessman and a writer who separated when she was a child and later divorced, she was raised in a matriarchal household that included her maternal grandmother, her mother, Vanne, some aunts and her sister, Judy.

She demonstrated an affinity for nature from a young age, filling her bedroom with worms and sea snails that she rushed back to their natural homes after her mother told her they would otherwise die.

When she was about 5, she disappeared for hours to a dark henhouse to see how chickens laid eggs, so absorbed that she was oblivious to her family’s frantic search for her. She did not abandon her study until she observed the wondrous event.

“Suddenly with a plop, the egg landed on the straw. With clucks of pleasure the hen shook her feathers, nudged the egg with her beak, and left,” Goodall wrote almost 60 years later. “It is quite extraordinary how clearly I remember that whole sequence of events.”

When finally she ran out of the henhouse with the exciting news, her mother did not scold her but patiently listened to her daughter’s account of her first scientific observation.

Later, she gave Goodall books about animals and adventure — especially the Doctor Dolittle tales and Tarzan. Her daughter became so enchanted with Tarzan’s world that she insisted on doing her homework in a tree.

“I was madly in love with the Lord of the Jungle, terribly jealous of his Jane,” Goodall wrote in her 1999 memoir, “Reason for Hope: A Spiritual Journey.” “It was daydreaming about life in the forest with Tarzan that led to my determination to go to Africa, to live with animals and write books about them.”

Her opportunity came after she finished high school. A week before Christmas in 1956 she was invited to visit an old school chum’s family farm in Kenya. Goodall saved her earnings from a waitress job until she had enough for a round-trip ticket.

Jane Goodall gives a little kiss to Tess, a 5- or 6-year-old female chimpanzee, in 1997.

(Jean-Marc Bouju / Associated Press)

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She arrived in Kenya in 1957, thrilled to be living in the Africa she had “always felt stirring in my blood.” At a dinner party in Nairobi shortly after her arrival, someone told her that if she was interested in animals, she should meet Leakey, already famous for his discoveries in East Africa of man’s fossil ancestors.

She went to see him at what’s now the National Museum of Kenya, where he was curator. He hired her as a secretary and soon had her helping him and his wife, Mary, dig for fossils at Olduvai Gorge, a famous site in the Serengeti Plains in what is now northern Tanzania.

Leakey spoke to her of his desire to learn more about all the great apes. He said he had heard of a community of chimpanzees on the rugged eastern shore of Lake Tanganyika where an intrepid researcher might make valuable discoveries.

When Goodall told him this was exactly the kind of work she dreamed of doing, Leakey agreed to send her there.

It took Leakey two years to find funding, which gave Goodall time to study primate behavior and anatomy in London. She finally landed in Gombe in the summer of 1960.

On a rocky outcropping she called the Peak, Goodall made her first important observation. Scientists had thought chimps were docile vegetarians, but on this day about three months after her arrival, Goodall spied a group of the apes feasting on something pink. It turned out to be a baby bush pig.

Two weeks later, she made an even more exciting discovery — the one that would establish her reputation. She had begun to recognize individual chimps, and on a rainy October day in 1960, she spotted the one with white hair on his chin. He was sitting beside a mound of red earth, carefully pushing a blade of grass into a hole, then withdrawing it and poking it into his mouth.

When he finally ambled off, Goodall hurried over for a closer look. She picked up the abandoned grass stalk, stuck it into the same hole and pulled it out to find it covered with termites. The chimp she later named David Graybeard had been using the stalk to fish for the bugs.

“It was hard for me to believe what I had seen,” Goodall later wrote. “It had long been thought that we were the only creatures on earth that used and made tools. ‘Man the Toolmaker’ is how we were defined …” What Goodall saw challenged man’s uniqueness.

When she sent her report to Leakey, he responded: “We must now redefine man, redefine tool, or accept chimpanzees as human!”

Goodall’s startling finding, published in Nature in 1964, enabled Leakey to line up funding to extend her stay at Gombe. It also eased Goodall’s admission to Cambridge University to study ethology. In 1965, she became the eighth person in Cambridge history to earn a doctorate without first having a bachelor’s degree.

In the meantime, she had met and in 1964 married Hugo Van Lawick, a gifted filmmaker who had traveled to Gombe to make a documentary about her chimp project. They had a child, Hugo Eric Louis — later nicknamed Grub — in 1967.

Goodall later said that raising Grub, who lived at Gombe until he was 9, gave her insights into the behavior of chimp mothers. Conversely, she had “no doubt that my observation of the chimpanzees helped me to be a better mother.”

She and Van Lawick were married for 10 years, divorcing in 1974. The following year she married Derek Bryceson, director of Tanzania National Parks. He died of colon cancer four years later.

Within a year of arriving at Gombe, Goodall had chimps literally eating out of her hands. Toward the end of her second year there, David Graybeard, who had shown the least fear of her, was the first to allow her physical contact. She touched him lightly and he permitted her to groom him for a full minute before gently pushing her hand away. For an adult male chimpanzee who had grown up in the wild to tolerate physical contact with a human was, she wrote in her 1971 book “In the Shadow of Man,” “a Christmas gift to treasure.”

Jane Goodall plays with Bahati, a 3-year-old female chimpanzee, at the Sweetwaters Chimpanzee Sanctuary, north of Nairobi, on Dec. 6, 1997.

(Jean-Marc Bouju / Associated Press)

Her studies yielded a trove of other observations on behaviors, including etiquette (such as soliciting a pat on the rump to indicate submission) and the sex lives of chimps. She collected some of the most fascinating information on the latter by watching Flo, an older female with a bulbous nose and an amazing retinue of suitors who was bearing children well into her 40s.

Her reports initially caused much skepticism in the scientific community. “I was not taken very seriously by many of the scientists. I was known as a [National] Geographic cover girl,” she recalled in a CBS interview in 2012.

Her unorthodox personalizing of the chimps was particularly controversial. The editor of one of her first published papers insisted on crossing out all references to the creatures as “he” or “she” in favor of “it.” Goodall eventually prevailed.

Her most disturbing studies came in the mid-1970s, when she and her team of field workers began to record a series of savage attacks.

The incidents grew into what Goodall called the four-year war, a period of brutality carried out by a band of male chimpanzees from a region known as the Kasakela Valley. The marauders beat and slashed to death all the males in a neighboring colony and subjugated the breeding females, essentially annihilating an entire community.

It was the first time a scientist had witnessed organized aggression by one group of non-human primates against another. Goodall said this “nightmare time” forever changed her view of ape nature.

“During the first 10 years of the study I had believed … that the Gombe chimpanzees were, for the most part, rather nicer than human beings,” she wrote in “Reason for Hope: A Spiritual Journey,” a 1999 book co-authored with Phillip Berman. “Then suddenly we found that the chimpanzees could be brutal — that they, like us, had a dark side to their nature.”

Critics tried to dismiss the evidence as merely anecdotal. Others thought she was wrong to publicize the violence, fearing that irresponsible scientists would use the information to “prove” that the tendency to war is innate in humans, a legacy from their ape ancestors. Goodall persisted in talking about the attacks, maintaining that her purpose was not to support or debunk theories about human aggression but to “understand a little better” the nature of chimpanzee aggression.

“My question was: How far along our human path, which has led to hatred and evil and full-scale war, have chimpanzees traveled?”

Her observations of chimp violence marked a turning point for primate researchers, who had considered it taboo to talk about chimpanzee behavior in human terms. But by the 1980s, much chimp behavior was being interpreted in ways that would have been labeled anthropomorphism — ascribing human traits to non-human entities — decades earlier. Goodall, in removing the barriers, raised primatology to new heights, opening the way for research on subjects ranging from political coalitions among baboons to the use of deception by an array of primates.

Her concern about protecting chimpanzees in the wild and in captivity led her in 1977 to found the Jane Goodall Institute to advocate for great apes and support research and public education. She also established Roots and Shoots, a program aimed at youths in 130 countries, and TACARE, which involves African villagers in sustainable development.

She became an international ambassador for chimps and conservation in 1986 when she saw a film about the mistreatment of laboratory chimps. The secretly taped footage “was like looking into the Holocaust,” she told interviewer Cathleen Rountree in 1998. From that moment, she became a globe-trotting crusader for animal rights.

In the 2017 documentary “Jane,” the producer pored through 140 hours of footage of Goodall that had been hidden away in the National Geographic archives. The film won a Los Angeles Film Critics Assn. Award, one of many honors it received.

In a ranging 2009 interview with Times columnist Patt Morrison, Goodall mused on topics from traditional zoos — she said most captive environments should be abolished — to climate change, a battle she feared humankind was quickly losing, if not lost already. She also spoke about the power of what one human can accomplish.

“I always say, ‘If you would spend just a little bit of time learning about the consequences of the choices you make each day’ — what you buy, what you eat, what you wear, how you interact with people and animals — and start consciously making choices, that would be beneficial rather than harmful.”

As the years passed, Goodall continued to track Gombe’s chimps, accumulating enough information to draw the arcs of their lives — from birth through sometimes troubled adolescence, maturity, illness and finally death.

She wrote movingly about how she followed Mr. McGregor, an older, somewhat curmudgeonly chimp, through his agonizing death from polio, and how the orphan Gilka survived to lonely adulthood only to have her babies snatched from her by a pair of cannibalistic female chimps.

Jane Goodall in San Diego.

(Sam Hodgson / San Diego Union-Tribune)

Her reaction in 1972 to the death of Flo, a prolific female known as Gombe’s most devoted mother, suggested the depth of feeling that Goodall had for the animals. Knowing that Flo’s faithful son Flint was nearby and grieving, Goodall watched over the body all night to keep marauding bush pigs from violating her remains.

“People say to me, thank you for giving them characters and personalities,” Goodall once told CBS’s “60 Minutes.” “I said I didn’t give them anything. I merely translated them for people.”

Woo is a former Times staff writer.