June 7, 2006

Australian rocks show early signs of life on Earth

LONDON (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 said on

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

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 analyzed 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