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. "Jane was passionate about empowering young people to become involved in conservation and humanitarian projects and she led many educational initiatives focused on both wild and captive chimpanzees," the institute wrote in a statement. "[Her] discoveries as an ethologist revolutionized science. She was always guided by her fascination with the mysteries of evolution, and her staunch belief in the fundamental need to respect all forms of life on Earth." Born in April 1934, Goodall loved nature and wildlife from a very young age, so much so that her father once gave her a stuffed monkey doll that young Jane named Jubilee and kept for the rest of her life. Goodall found an early mentor in paleoanthropologist Louis Leakey, who employed her as a secretary at the National Museum in Nairobi. She accompanied Leakey and his wife, Mary Leakey, on a hunt for fossils at the Olduvai Gorge. Impressed with the young woman's potential, Leakey sent her to Tanzania to study chimpanzees in the Gombe forest. He also arranged for her to enter the PhD program in ethology at Cambridge University; Goodall completed her PhD in 1965 with a thesis based on that initial Gombe study. The research program she founded is still active today. Goodall's approach to studying chimps was controversial because she defied the traditional practice of numbering the animals, giving them names instead, which many in what was then a male-dominated field thought demonstrated a lack of objectivity. Leakey, however, found her insights valuable. His faith in his protégé was rewarded in 1960 when Goodall observed a chimp named David Greybeard bend a twig, strip off the leaves, and use it to spoon termites out of a nest and into his mouth. Until then, researchers had assumed that humans were the only ones capable of tool use. When he learned of the behavior, Leakey famously observed, "Now we must redefine 'tool,' redefine 'man,' or accept chimpanzees as humans."