Ars Technica: An analysis of sulfur isotopes in rocks from the Strelley Pool Formation in Australia lends support for the idea that life arose very soon after Earth’s formation. By comparing the ratios of 32S, 33S, and 34S throughout the layers of the rocks, researchers determined when the quantities of the isotopes could have been produced by living organisms. Although that isn’t enough evidence to conclude that biofilms—thin layers of single-celled organisms—were the source of the sulfur, it is a building block for further study. The 3.5-billion-year date is just 1 billion years after Earth was formed and only 300 million years after the end of a period during which the planet was heavily bombarded by meteors. More significantly, it’s 800 million years before the first evidence of complex biological life forms.