Australian Aboriginal culture includes a number of practices and ceremonies centered on a belief in the Dreamtime and other mythology. Reverence and respect for the land and oral traditions are emphasised. Over 300 Languages and other groupings have developed a wide range of individual cultures. Due the colonization of Australia under terra nullius concept these cultures were treated as one monoculture. Australian Aboriginal art has existed for thousands of years and ranges from ancient rock art to modern watercolour landscapes. Aboriginal music has developed a number of unique instruments. Contemporary Australian Aboriginal music spans many genres. Aboriginal peoples did not develop a system of writing before colonisation, but there was a huge variety of languages, including sign language