 Joyner's interest has been in the nineteenth century phenomenon known as the yahoo (also called the hairy man, Australian ape or Australian gorilla), a shadowy creature then seen as an undiscovered marsupial but one that was presumably extinct by the early twentieth century.There is some evidence for its former existence (Joyner 2008, p. 109).His 1977 book "The Hairy Man of South Eastern Australia" is a collection of documents about the yahoo.