Scientists have identified evidence of biological activity preserved inside a roughly 3.5-billion-year-old rock from eastern India, providing what researchers describe as probably the earliest biomolecular evidence of life ever detected on Earth. The evidence comes from ancient rocks of the Singhbhum Craton, a vast geological formation stretching across parts of Jharkhand and Odisha.
In a study published in the Proceedings of the National Academy of Sciences (PNAS), researchers analysed hundreds of modern and ancient organic samples using pyrolysis gas chromatography-mass spectrometry and supervised machine learning. The technique allowed them to distinguish patterns associated with material produced by living organisms from material formed through non-biological processes.
Among the samples was material from the approximately 3.51-billion-year-old Singhbhum Craton. The analysis classified organic molecules preserved in one of the two Indian samples as biogenic, meaning their chemical signature was consistent with having originated from ancient life.
Researchers described this as the earliest biomolecular evidence for the biological origin of organic matter found among the samples examined. What the Evidence Shows: The finding does not mean scientists have uncovered intact 3.5-billion-year-old microbes. Instead, billions of years of heat, pressure and geological change have broken down the original biological molecules, leaving behind altered chemical fragments that researchers were able to analyse.
The rock, a “black-and-white” banded chert from Bhitardari, pairs a firm age with several independent chemical and structural signs that its carbon was made by living organisms. The δ^13C isotope data of the carbonaceous matter, together with stratigraphic relationships, indicate a biogenic origin of the kerogen, making this the oldest directly dated rock with a confirmed biosignature.
Ancient Volcanic Marine Environment: The landscape in which these organisms existed would have looked almost nothing like India today. Geological studies of the Singhbhum Craton show that between about 3.5 and 3.3 billion years ago, much of the region consisted of volcanic terrain beneath ancient oceans.
Frequent submarine eruptions produced lava and sedimentary deposits that were eventually preserved within the craton. The primordial microorganisms thrived on heat from ancient, silica-rich underwater hydrothermal vents, which created a unique ecosystem. The rock contains tiny black bands interpreted as fossilised microbial mats, with analysis suggesting the organisms were already converting carbon dioxide into organic matter billions of years ago.
According to the study, researchers date the Bhitardari chert, a hard, silica-rich rock from the Bhitardari area, to 3.497 billion years ago. The rock was dated using zircon crystals, and special tests confirmed the carbon inside came from living things, not random chemistry.
The discovery could be the oldest evidence of organic life ever dated in a rock: it would be biological matter from 3.497 billion years ago, corresponding to the Paleoarchean. The research was led by scientists from the Geological Survey of India and collaborators, and the study has been published in the Proceedings of the National Academy of Sciences.
For science, the Singhbhum Craton’s 3.5-billion-year-old chert is a window into Earth’s earliest chapters, showing that life may have emerged very early in underwater volcanic environments, long before continents took their modern shape.
