LOS ANGELES -- World-renowned ethologist, primatologist, and conservationist Jane Goodall has died at the age of 91, the Jane Goodall Institute said Wednesday in a statement.

Goodall, a United Nations Messenger of Peace and founder of the institute, passed away of natural causes in California while on a speaking tour in the United States, the statement said.

Goodall's discoveries as an ethologist revolutionized science, and she was a tireless advocate for the protection and restoration of our natural world, the statement further said.

Born in Britain, Goodall rose to fame for her pioneering research on chimpanzees in Tanzania in the 1960s. Widely regarded as the world's foremost expert on chimpanzees, she devoted more than six decades to studying their social and family interactions in the wild.