Australia rocks show early signs of life on Earth

LONDON, June 8 (Reuters) Rock formations in Western Australia may not only be some of the earliest evidence of life on Earth but also the first signs of biodiversity, scientists have said.

Doubts about whether the formations known as stromatolites were signs of ancient life have persisted since they were described almost three decades ago.

Some scientists believe they were formed by micro-organisms that lived on Earth more than 3 billion years ago. Others argued that they were formed chemically from hydrothermal vents.

Abigail Allwood, of Macquarie University in Sydney, Australia, who studied the structures, said they show an early ecosystem and its response to environmental conditions spanning 80 million years.

''We believe that many different types of organisms may have coexisted at this time, so that we have not just the oldest evidence of life, but we also have the oldest evidence of biodiversity,'' she said in a statement.

Allwood and her colleagues analysed different stromatolites in rocks covering more than 10 km (6 miles) in length. Their findings are reported in the journal Nature.

The stromatolites varied in shape and each had their own environmental niche. Because of their complexity the researchers believe they could not have a chemical origin.

Dr Gregory Webb, of the Queensland University of Technology in Australia, said the research provides compelling evidence that the stromatolites are true fossils formed by some of the oldest forms of life on Earth.

''What is especially unique about their work is that they have been able to describe seven different microbial communities distributed through their natural environment,'' he said, adding that they documented the oldest known ecosystem.

Allwood said the next big question is about the nature of the micro-organisms that produced the formations. The research could be important in the search for life on other planets.

''If you're going to find anything on a planet like Mars it's going to be primitive and unlike anything we expect to see on our own planet today. It will likely be more like the type of micro-organisms that produced the early stromatolites,'' she added.

REUTERS SK VC0433