It was around 1.6 billion years ago that a community of small, bright red, plantlike life-forms, flitting around in a shallow pool of prehistoric water, were etched into stone until the end of time. Or at least until a team of Swedish researchers chipped their fossilized remnants out of a sedimentary rock formation in central India.
Research published this week in PLoS Biology suggests this collection of ancient, newly analyzed fossils—unearthed a few years back—are in all likelihood red algae. If that proves true, it would imply that complex, multicellular life evolved a lot earlier than previously thought—and that the evolutionary family tree of life on Earth might need a major pruning.
Earth’s first traces of life probably showed up around 3.5 billion years ago, a billion years or so after our planet formed. Just when these simple, single-celled organisms—classified as “prokaryotes” due to their lack of a nucleus—evolved into multicellular, nucleated forms called “eukaryotes” is a matter of debate. Alga, a eukaryote, is thought to be one of the oldest forms of complex life. And given that previous fossil finds had dated red algae back just 1.2 billion years, the new discovery could reset the evolutionary time line by nearly half a billion years.