In a modern context, Yowie is the generic (and somewhat affectionate) term for the unidentified hominid reputed to lurk in the Australian wilderness. It is, in other words, an Australian cryptid analogous to the Himalayan Yeti and the North American Bigfoot. Australian cryptozoologist Rex Gilroy has attempted to popularise the scientific term Gigantopithecus australis for the creature (without support from the Australian scientific community), based on his theory that they comprise a relic population of the extinct ape Gigantopithecus.
Rather confusingly, Yowie (or "Yowie-Whowie") is also the name of a completely different mythological character in native Australian aboriginal mythology folklore. This version of the Yowie is said to be a bizarre, hybrid beast resembling a cross between a lizard and an ant. It emerges from the ground at night to eat whatever it can find, including humans. This creature's characteristics and legend are sometimes interchangeable with those of the bunyip.
The origin of the term "Yowie" in the context of unidentified hominids is unclear. Some presume that it simply arose through confusion with the aforementioned aboriginal legend. On the other hand, Jonathan Swift's yahoos from Gulliver's Travels are sometimes cited as a source. The word "Yowie" was also apparently a slang term for the Orang-utan in Victorian England.
Sightings and Reports
Reports of ape-like Yowies go back as far as the 18th Century. The mid to late 19th Century saw a wealth of sightings, most describing a large, gorilla-like creature (albeit usually bipedal), which lived in remote mountainous or forested regions. Reports have continued to the present day with the trail of evidence following the pattern familiar to most unidentified hominids around the world- i.e. eyewitness accounts, mysterious footprints of hotly-disputed origin, and a frustrating lack of conclusive proof.
Researchers have likewise scoured Australian aboriginal mythology for evidence of the ape-like Yowie (as oppose to the hybrid creature described above), but definitive references to anything remotely similar are few and far between.