See also:

Molecular Fossils

Publications

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3.45 billion year old stromatolites in the Pilbara region (GSWA)

New Evidence of Life's Origins

Fossils suggest life began in deep-sea hot spring

Shark Bay stromatolites (picture)

Earliest Known Life on Earth
 

Earliest Fossils

The oldest fossil evidence for life on Earth is found in 3.5 billion year old rocks in the Pilbara region of Western Australia. Along with rocks of similar age in South Africa these are the oldest well preserved sedimentary rocks known. The evidence for fossil life takes the form of:

• structures called stromatolites which are believed to be the fossilized remains of laminated structures built by colonies of micro-organisms. Modern examples of such colonies are found in Shark Bay in Western Australia
• microfossils of individual micro-organisms.
• carbon isotope ratios indicative of biological activity.

Some recent results include the discovery of 3.45 billion year old stromatolites by scientists of the Geological Survey of Western Australia, and the reporting of microfossils from a deep sea hot spring deposit of age 3.2 billion years by Birger Rasmussen of the University of Western Australia.

While controversy surrounds many of the reports of fossils of this age, it is generally accepted that there is sufficient evidence to be reasonably sure that life was well established on earth at about 3.5byr ago. Older rocks at 3.8byr age in Greenland are too greatly deformed to preserve fossils but have been claimed to show evidence for life in their carbon isotope ratios.