How microbial fossils illuminate life's origins

More than 3.5 billion years ago, the Earth was not the hospitable world we know today. The atmosphere lacked oxygen, the seas were acidic and rich in iron, and volcanic activity roared across a barren landscape. Yet, in this alien world, something extraordinary happened—life emerged. The earliest life forms left behind no bones or shells, but they did leave other clues about their biology and impact on early Earth environments.