Ancient Indian Rock Shows 3. 5‑Billion‑Year Biological Signature

Scientists have measured carbon that is 3.5 billion years old in a rock from India. The rock comes from the Singhbhum Craton and holds clues about early life.

Tiny zircon crystals were pulled from the black‑and‑white banded Bhitardari chert in the Eastern Iron Ore greenstone belt. These zircons gave a lead‑lead age of 3497 ± 5 million years, based on four analyses with a good fit.

The chert is packed with carbon‑rich material in two styles. One style is ultra‑fine layers spread through the rock matrix, and the other is graphite flakes that fill later quartz veins. When scientists measured the carbon‑13 ratio of both styles, they got a value of –30.9 per mil, which points to a biological source.

This finding marks the first time a Paleoarchean rock with carbon and a direct date shows a clear biological fingerprint. The isotopic signal matches what we would expect if early microbes were already using advanced pathways like the Calvin cycle at that time.