Australian Aboriginal art is the oldest living art tradition in the world, with paintings in rock shelters dating back over 20,000 years. The art includes naturalistic paintings of human, plant and animal figures, as well as non-naturalistic, or "abstract" designs with concentric circles, "u" shapes, and lines. The naturalistic style, predominant in Arnhemland in northern Australia, is often characterised by "X-ray" art, where the internal organs of animals are depicted. The abstract style, predominant in central Australia, originates from sacred designs used in ceremonies. These designs, originally for body painting, ground painting, and carved on sacred stones and boards, are now painted on canvas. Much of Aboriginal art relates to stories of the Dreamtime. This Dreamtime is the Creation Period in Aboriginal belief, when important Ancestral Beings formed the land and created the people, plants and animals. These Ancestral Beings, often depicted in the art, may take human, animal, plant or combined forms, and taught the people their laws and ceremonies. (Courtesy Dr. David Welch.) Aboriginal Fine Arts Gallery is a founding member of the Australian Indigenous Art Trade Association, which was established to promote the ethical trade of indigenous art.