Australia: The Land Where Time Began

A biography of the Australian continent 

Precambrian Period [Archaean + Proterozoic] 4500-540 million years ago

During this period the only life found is either bacteria or algae, with some lower invertebrates occurring in the latter part of the Period. The Precambrian is further divided into 2 Eons, the Archaean Eon (4500-2500 Ma) and the Proterozoic Eon (2500-540 mya).

The Archaean Eon is the time when the first known signs of life appear in the rock strata. The very first known are blue-green algae (cyanobacteria) which formed domed structures called stromatolites. Fossils of even older bacteria that preceded the cyanophytes that formed the stromatolites have been found in Western Australia.

At about 750 Ma there was an extensive ice age, and after the glaciers retreated at the end of this ice age seems to be the time when the first metazoans are seen in the fossil record, though they would no doubt have been present for some time, but not in a form that could fossilise easily.

In the Proterozoic Eon ("first life"), as well as single-celled bacteria (no nucleus) and algae (with a nucleus), the first known multi-celled organisms (metazoans) appear. At a site in the Flinders Ranges of South Australia, Ediacara Hills, has been found what is so far the earliest known fossils of soft-bodied animals. They resemble jelly fish, worms and corals.  see Ediacaran Fauna

Sources & Further reading

1. Mary E. White, The Nature of Hidden Worlds, Reed, 1993