For much of Earth’s history, life was just single cells, and stromatolite fossils are mounds of carbonate constructed by these communities of microbes. “The significance of stromatolites is that not only do they provide obvious evidence of ancient life that is visible with the naked eye, but that they are complex ecosystems,” Professor Nutman said. “This indicates that as long as 3.7 billion years ago microbial life was already diverse. This diversity shows that life emerged within the first few hundred millions years of Earth’s existence, which is in keeping with biologists’ calculations showing the great antiquity of life’s genetic code.”
— source media.uow.edu.au | Aug 31, 2016