India discovery: 3.5-billion-year-old microbial life directly dated

Geologists have achieved a breakthrough by directly dating 3.5-billion-year-old evidence of microbial life found in the Singhbhum Craton of eastern India. Led by Trisrota Chaudhuri of the Geological Survey of India, the research team analyzed carbonaceous chert from the Bhitardari outcrop.

Unlike previous studies that estimated the age of microbial structures based on surrounding rock layers, this study successfully linked organic biosignatures directly to radioactive zircon crystals. The zircons, which were deposited alongside volcanic ash, allowed for precise radiometric dating.

Using Raman spectroscopy and carbon isotope analysis, researchers confirmed that the carbonaceous layers experienced temperatures between 324 and 369 degrees Celsius, consistent with the original rock formation. The findings, published in the Proceedings of the National Academy of Sciences, suggest that complex metabolic pathways may have existed in ancient marine environments rich in iron and silica nearly 3.5 billion years ago.