In the Dreamtime Ancestral Beings walked through the desert, alone or in groups, teaching law and ceremony to Aborigines living at isolated camps. They created sacred sites such as hills and rocky outcrops, which changed the shape of the hitherto flat landmass. Trees, plants and seeds were distributed to these isolated groups, thus ensuring their survival of the desert.
Ancestral beings who felt they were in danger or that it was time for them to die could transform themselves into other creatures or metamorphose into rocks, hills, plants and trees in which their spirits would Iive on forever.
Today ceremonies honouring these spirits are still performed at sacred sites. Yala was a yam ancestor who travelled throughout the desert in his human form, creating increased centres of wild bush potatoes in the form of sweet yams.
One of the main centres was at a place called Yaldiyaal, west of Alice Springs. When Yala felt too tired to continue living he lay down at this place and changed into a yam, sending out roots from which tubers eventually grew in all directions. Ceremonies are regularly held at this site to ensure that good supplies of yams will continue throughout the seasons.