Famed scientist Jane Goodall has died. She was 91. Goodall was best known for her groundbreaking discoveries about chimpanzee behavior, but she dedicated much of her career to causes like environmentalism and animal welfare.

Goodall first observed wild animals and took notes about them as a child in England. It wasn’t long before she decided on a career in animal behavior. In 1960, when Goodall was 26, she was hired by the scientist Louis Leakey to study wild chimpanzees in what is now the African nation of Tanzania. 

Goodall’s chimpanzee observations led to several discoveries. For example, she observed a chimpanzee named David Greybeard removing the leaves from a stick and then dipping the stick into a termite mound to capture the insects. This was the first time a scientist noted an animal using a tool. 

“The reason why this was so exciting was because, at that time, it was thought by Western science that only humans used and made tools,” Goodall once explained. Scientists have since observed several other animals using tools.

Goodall found that each chimpanzee had its own personality. She also learned that chimps have complex emotions. This observation surprised some scientists, but not Goodall. She later said she expected chimps to have complex emotions because her childhood dog, Rusty, had them too.

“We all know that [dogs] can be happy, sad, fearful and that they’re highly intelligent,” she pointed out. Goodall’s discoveries led to a new understanding of chimpanzees. Support grew for protecting the forests and grasslands where chimps live.

Goodall became world famous. She used that fame to speak out in support of animal welfare and conservation. In 1977, Goodall founded the Jane Goodall Institute to help promote conservation. And until her death, she traveled the globe to talk about the importance of protecting the natural world. 

Goodall’s tireless work for the planet and all living things made her a hero to people of all ages. After her death, tributes poured in from scientists, politicians, actors, and many more. 

“Jane Goodall was the first to prove that an investigating scientist and a great ape living in the wild could become true friends,” said British scientist David Attenborough. “In doing so, she came to [change] our understanding of chimpanzees.”

Click through the slideshow for photos from Jane Goodall’s life and career.