Since the early 1970s, scientists have been measuring the δ13C of organic carbon from Precambrian rocks (e.g., Schopf and Klein, 1992). Geologists were soon searching the world over for older and older rocks resting exposed on the surface that might contain evidence of the first signs of life. Greenland’s Isua rocks were first scrutinised in the 1980s by Cyril Ponneperuma and his student Cliff Walters. Walters was given the task of examining the organic geochemistry of the Isua rocks. His professor wanted him to discover something revolutionary, perhaps Earth’s earliest evidence of life. Cliff struggled...

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