New evidence suggests life on Earth began at least 3.7 billion years ago

Washington Post : Melting snowpack in Greenland has revealed what might be the oldest microbial structures yet discovered. Allen Nutman of the University of Wollongong in Australia and colleagues found the fossils in July 2012 in Isua, a remote area on the island that has some of the oldest rocks on Earth. Called stromatolites, the structures are about 1–4 cm high and formed in shallow water by the accretion of sedimentary grains by microorganisms. The scientists estimate the stromatolites to be about 3.7 billion years old, 200 million years older than a previous find in Western Australia. Because the organisms that formed the structures would have been capable of photosynthesis, a fairly evolved mechanism, it is unlikely they represent the first life on the planet. The discovery means life may have developed much earlier on Earth than previously believed, and it could have implications for the development of life elsewhere in the universe. Researchers say more Greenland stromatolites may turn up as the island’s ice sheet continues to melt due to climate change.