Strange rock formations in Australia were produced by the earliest known lifeforms which lived 3,430 million years ago, scientists have said.
The formations are known as stromatolites and the latest study, published in Nature, has found convincing evidence that they were produced by marine microbes - perhaps the first living organisms on earth.
Scientists studied rock outcrops more than 6 miles in length in Pilbara Craton, Western Australia, covering a time period in prehistory of about 80 million years, according to Abigail Allwood of the Australian Centre for Astrobiology at Macquarie University in Sydney.
"This has shed light on the conditions that nurtured very early life, and we can use that to predict where life might have emerged on other planets," Ms Allwood said. "Our next big question is about the nature of the micro-organisms that produced these structures.
"We believe that many types of organisms may have coexisted at this time, so that we have not just some of the oldest evidence of life, but we also have the oldest evidence of biodiversity"
Arthur Hickman of the Geological Survey in Western Australia said: "Whether or not these strange formations were created by the first known microbes on Earth or purely by geological or chemical processes has been a subject of ongoing controversy."
The study is strong evidence that the formations are indeed fossilised lifeforms that may have generated the atmospheric oxygen that was subsequently used by other living organisms.
"The microbes that created the Pilbara stromatolites probably produced oxygen and thus are likely to have added to the content of the atmosphere as much as 3.5 billion years ago," Dr Hickman said.