Precambrian Time

It is not known when life originated, but carbon in 3800 million year old rocks from islands off western Greenland may be of organic origin. Well-preserved bacteria older than 3460 million years have been found in Western Australia. Probable fossils 100 million years older have been found in the same area. There is a fairly solid record of bacterial life throughout the remainder of the Precambrian.

Excepting a few contested reports of much older forms from Texas and India, the first complex multicelled life forms seem to have appeared roughly 600 Ma. A quite diverse collection of soft-bodied forms is known from a variety of locations worldwide between 542 and 600 Ma. These are referred to as Ediacaran or Vendian biota. Hard-shelled creatures appeared toward the end of that timespan.

A very diverse collection of forms appeared around 544 Ma, starting in the latest Precambrian with a poorly understood small shelly fauna and ending in the very early Cambrian with a very diverse, and quite modern Burgess fauna, the rapid radiation of forms called the Cambrian explosion of life.

Precambrian era which includes the Proterozoic eon and the Archean eon spanning about 2000 years each, that single celled organisms like blue-green algae and bacteria, first appeared. Towards the end of the Archean eon the first multicellular, soft bodied animals began to emerge such as jellyfish, seapens, and worms.

Fossils from the late Precambrian include those of the Ediacaran fauna, named for an Australian range of hills. Paleontologist once thought that these flattened, soft-bodied forms represent an evolutionary dead end, but they now believe these animals maybe related to other later animals. Pteridinium, was a few centimeters long. Contemporary with the Ediacaran fauna were some early shelled animals, such as Cloudina and Sinotubulites, which attached themselves to the floors of shallow seas.