
In 1960, she made her most famous discovery: watching a male chimpanzee, whom she named David Greybeard, use a stick to fish for termites. This observation upended the long-held scientific belief that only humans made and used tools, prompting her mentor, Louis Leakey, to state, "Now we must redefine 'tool,' redefine 'man,' or accept chimpanzees as humans".
After attending a primatology conference in 1986 where she learned about widespread habitat destruction, Goodall shifted her focus from research to conservation and activism. For the last four decades of her life, she traveled nearly 300 days a year, speaking globally about the climate crisis and the importance of conservation.