New Oldest Fossils

Fossils discovered in Australian rocks may be the remnants of three and a half billion-year-old microorganisms.

Aug 22, 2011
Jef Akst

Parts of two microfossils occurring with numerous crystals of pyrite.DAVID WACEY

New fossils discovered on an ancient inland beach in Western Australia are pushing back the timing of life's origin on Earth. Martin Brasier, a palaeobiologist at the University of Oxford, UK, and his collaborators found what appears to be fossils of cells in black sandstone dating to 3.4 billion years ago, according to the paper published in Nature Geoscience yesterday (August 21).

Proving that the traces actually are an example of the planet's earliest life is not easy, however. Previously discovered "fossils" dating to the same period turned out to be the remains of inorganic materials. But Brasier believes these new fossils are the real deal. They range in size from 5 to 80 micrometers in diameter, and are shaped like spheres and elongated rods. Furthermore, they're ringed by walls of uniform thickness, and have levels of carbon-13 indicative of biological carbon fixation.

"This goes some way to resolving the controversy over the existence of life forms very early in Earth's history," Brasier told Nature. "The exciting thing is that it makes one optimistic about looking at early life once again."