Scientist and conservationist Dr Jane Goodall has died, aged 91.

The news was announced on the Jane Goodall Institute social media pages, saying she passed away from natural causes.

She was in California as part of her speaking tour.

“Dr Goodall’s discoveries as an ethologist revolutionised science, and she was a tireless advocate for the protection and restoration of our natural world,” the post read.

Dr Goodall was considered the world’s foremost expert on chimpanzees.

Goodall was born in London in 1934 and had an interest in animal behaviour from a young age, according to the britannica.com.

After leaving school at 18 she worked as a secretary and a film production assistant to save for her boat ticket to Africa in 1957, where she helped paleontologist and anthropologist Louis Leakey after impressing him with her knowledge of the continent and its wildlife.

When they began a study of wild chimpanzees on the shore of Lake Tanganyika, British authorities resisted the idea of a young woman living among wild animals in Africa, according to The Jane Goodall Institute New Zealand.

“They finally agree to Leakey’s proposal when Jane’s mother Vanne volunteers to accompany her daughter for the first three months.“

In July 1960, Goodall and her mother arrived on the shores of Gombe Stream Chimpanzee Reserve in western Tanzania.

The chimpanzees initially fled Goodall in fear, according to the institute.

“With patience and determination she searched the forest every day, deliberately trying not to get too close to the chimpanzees too soon. Gradually the chimpanzees accepted her presence.”

In October 1961, Goodall observed chimpanzees eating meat, and later watched them hunt for meat, disproving the widely held belief chimpanzees are vegetarian.

The next month she saw two chimpanzees making tools to extract termites from their mounds, according to the institute.

After selecting a thin branch they’d strip the leaves and push it into the termite mound, pulling it out a few seconds later to eat the termites that now covered the stick.

“This becomes one of Jane’s most important discoveries. Until that time, only humans were thought to create tools.“

On hearing of Jane’s observation, Leakey said: “Now we must redefine tool, redefine Man, or accept chimpanzees as humans.”

Goodall’s work in Gombe soon became more widely known and in 1962 she was accepted at Cambridge University as a PhD candidate, despite not having a university degree. She’d earn her PhD in ethology - the study of animal behaviour - in 1965.

“Some scholars and scientists give Jane a cold reception and criticise her for giving the chimpanzees names, saying it would’ve been more “more scientific to give them numbers”, according to the institute.

“Jane had to defend an idea that might now seem obvious: that chimpanzees have emotions, minds and personalities.”

The Gombe Stream Research Centre was established in 1965 after National Geographic paid for permanent buildings on the site and in 1977 Goodall founded the Jane Goodall Institute for Wildlife Research, Education and Conservation.

In 1984, she started work on “ChimpanZoo”, an international research programme by her institute to study captive chimpanzees and improve their lives through research, education and enrichment, according to the institute.

Two years later, Goodall decided to switch her attention from Gombe to conservation efforts for wild chimpanzees, after learning the extent of habitat destruction across Africa during a scientific conference.

- More to come.