Earth's oldest evidence of life is written in stone—but it's at risk of disappearing

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Today, our planet is teeming with life, but it has not always looked the same. Long before forests reached skyward, animals walked on land and dinosaurs rose and fell, our planet was shaped by a much smaller, more unassuming form of life.

And we can still find traces of it today. These ancient fossils, the earliest visible evidence of life on Earth, are known as microbialites. Western Australia contains an extraordinary record of microbialites: from the oldest known examples, preserved in rocks almost 3.5 billion years old in the Pilbara, to living examples in the UNESCO World Heritage area of Shark Bay.

Our review of 50 years of microbialite research in Western Australia, published today in the journal Alcheringa, summarizes what this archive can tell us about the evolution and resilience of life on Earth. Despite a fossil record that spans billions of years, microbialites are surprisingly fragile. Fossil sites remain vulnerable to overcollection and degradation, while living microbialites are facing growing pressures.

At sites such as Lake Clifton and Shark Bay, some events may have already caused irreparable damage. One such example was in May 2024, when dozens of aurora chasers trampled 2,000-year-old thrombolites in a restricted area at Lake Clifton. Microbialites are mounded structures that come in many shapes and sizes.

They form when communities of microbes either precipitate minerals or trap and bind sediment. Types of microbialites can be characterized by their internal structure. Stromatolites are the best known and have distinctive layers.

Thrombolites, by contrast, have a clotted texture. The microbialite record can tell us a great deal about life on Earth. It gives us clues about where some of the earliest life lived, where we might look for life beyond Earth and how our atmosphere became oxygen rich, paving the way for more complex life to follow.