Image: Peter Trusler
Source: Courtesy Australia Post
560 million years ago.
Image: Ron Blakey. Altered by Cally Bennet and Fons VandenBerg
Source: Colorado Plateau Geosystems
It is hard to imagine our planet without animal life. Yet for most of the Earth’s existence the only kind of life has been single-celled organisms like bacteria. After some of these evolved the ability to photosynthesise, they slowly transformed the Earth’s atmosphere over billions of years by producing oxygen. An atmosphere with higher levels of oxygen set the stage for a revolutionary change to life – the development of bodies made of many cells.
The Ediacara Hills in the Flinders Ranges have given their name to the Ediacaran – the geological period when the first clearly multicellular life appears in the fossil record. It is the only geological period defined by an Australian site.
The earliest fossils of these multi-celled animals are preserved in rocks that are about 575 million years old. These animals had no hard shells or skeletons, and the impressions left by their soft bodies are difficult to interpret. There is much scientific debate about what kinds of organisms they were, but most of them were probably not the ancestors of any animals living today.
During the Ediacaran period, the world looked very different from today – there was a single giant continent surrounded by an enormous sea. Areas of what would become Australia were part of this continent and were in the northern hemisphere near the equator. The eastern coast of this ancient continent ran through what is now South Australia. If you travelled back in time you would not be able to find ‘Victoria’ as dry land at all.