Legendary primatologist Jane Goodall, whose immersive field research living among chimpanzees in the 1960s essentially redefined the relationship between humans and animals, has died at the age of 91. According to the Jane Goodall Institute (JGI), Goodall died of natural causes while in California as part of a US speaking tour. Goodall found an early mentor in paleoanthropologist Louis Leakey, who employed her as a secretary at the National Museum in Nairobi. Impressed with the young woman's potential, Leakey sent her to Tanzania to study chimpanzees in the Gombe forest. When he learned of the behavior, Leakey famously observed, "Now we must redefine 'tool,' redefine 'man,' or accept chimpanzees as humans."