Researchers have identified some of the oldest evidence of oxygen-producing life on Earth, uncovering chemical traces in rocks at least 2.5 billion years old, and additional biological signatures in 3.3 billion-year-old material. The discovery pushes back the record for ancient photosynthetic organisms by nearly a billion years.
The team, led by Dr. Robert Hazen and Dr. Katie Maloney, used machine learning algorithms to detect subtle chemical "whispers" in rocks, which indicate the presence of ancient life. These algorithms were trained to distinguish biological signals from modern plant, animal, and even meteoritic molecules, achieving a 90% accuracy rate.
"Ancient life leaves more than fossils; it leaves chemical echoes," says Hazen. Maloney adds that this technique allows scientists to "read the deep time fossil record in a new way" and could help guide the search for life on other planets. The findings may also shed light on the origins of the Great Oxygenation Event, when Earth's atmosphere began accumulating oxygen around 2.4 billion years ago.
Prior to this discovery, the oldest reliably identified photosynthetic life dated back 1.7 billion years. By extending this range, the research provides new insights into the early evolution of life on Earth and the potential for ancient life elsewhere in the solar system. The study is published in the Proceedings of the National Academy of Sciences.