As far as we know, life originated on Earth about 3.5 billion years ago, and for roughly the first 3 billion years of that history all life was microscopic. Then, during the Ediacaran Period from 635 million to 541 million years ago, the first organisms visible to the naked eye emerged. Although many members of this group, called the Ediacara biota, would have looked alien to us, some nonetheless had features we might find familiar. And according to a new study, it was Ediacaran creatures that left behind Earth’s oldest-known footprints.