Samples of rare and exceptionally well-preserved seaweed fossils.
A new chemical technique combined with artificial intelligence made it possible to distinguish patterns that were impossible to identify through human observation alone: it identified molecular signals of biological origin in rocks that are more than 3.3 billion years old.
The timeline of life on our planet was completely shaken on Monday, by an international study, in the Proceedings of the National Academy of Sciences.
Researchers at the Carnegie Institution for Science developed a methodology that combines advanced chemistry with artificial intelligence (AI), which made it possible to identify molecular signals of biological origin in rocks more than 3.3 billion years old.
The results thus suggest that life on Earth may have emerged at least a billion years earlier than previously thought.
The advance stems from an unprecedented approach: instead of looking for preserved biomolecules, normally destroyed by hundreds of millions of years of pressure, heat and geological transformations, researchers analyzed the fragmentation and degradation patterns that these molecules leave behind.
Even when the original compounds disappear, their “chemical echoes” remain and can reveal whether the organic matter had a biological origin or not.
The team analyzed 406 very different samples, from modern organisms and ancient fossils to meteorites and synthetic organic mixtures. All were subjected to pyrolysis gas chromatography–mass spectrometry, a technique that intensely heats the material to release and identify its chemical components. The resulting data fed machine learning models capable of distinguishing patterns impossible to identify through human observation alone.
The models were able to differentiate organic matter of biological origin from non-biological samples with a 93% accuracy. When comparing modern organisms with meteorite materials, the hit rate reached 100%.
The team identified clear signs of biological origin in 11 very old geological samples. The most significant belongs to the Josefsdal Chert, in the Barberton Greenstone Belt, in South Africa: sedimentary rocks 3.33 billion years old that now reveal unequivocal chemical evidence of life.
Molecular signatures of photosynthesis were also detected in 2.52 billion-year-old rocks from the Gamohaan Formation, also in South Africa, chemically supporting what paleontologists have suspected for decades: that certain three-dimensional carbonate structures preserved in that formation (microbialites) represent extremely ancient photosynthetic microbial communities.
The same technique also made it possible to identify signs of photosynthesis in 2.30 billion-year-old rocks from the Gowganda Formation, in Canada.
Until now, the oldest reliably detected molecular traces of life went back only about 1.6 billion years. The new approach has doubled this time window and suggests a much earlier chronology for the early evolution of Earth’s biosphere.
In simpler terms, Earth may have supported life and photosynthetic life much earlier than any previous hypothesis could demonstrate.
It is knowledge that will help us analyze samples from Mars or icy moons such as Europa and Enceladus, where future missions intend to look for signs of life, believe the authors of the study, cited by .
