Longer days on early Earth set stage for complex life.

Today, oxygen fuels much of life on Earth, but it wasn9t always that way. Three billion years ago, this gas was scarce in the atmosphere and oceans. Knowing why oxygen became plentiful could illuminate the evolution of our planet9s flora and fauna, but scientists have struggled to find an explanation satisfying to all. Now, a research team has proposed a novel link between how fast our planet spun on its axis—which defines the length of a day—and the ancient production of additional oxygen. Their modeling of Earth9s early days, which incorporates evidence from microbial mats coating the bottom of a shallow, sunlit sinkhole in Lake Huron, produced a surprising conclusion: As Earth9s spin slowed and led to longer days, that could have triggered more photosynthesis from similar mats, allowing oxygen to build up in ancient seas and diffuse up into the atmosphere.