EVIDENCE FOR LIFE ON EARTH BEFORE 3,800 MILLION YEARS AGO

IT is unknown when life first appeared on Earth. The earliest known mi crofossils (similar to 3,500 Myr before present) are structurally comp lex, and if it is assumed that the associated organisms required a lon g time to develop this degree of complexity, then the existence of lif e much earlier than this can be argued(1,2). But the known examples of crustal rocks older than similar to 3,500 Myr have experienced intens e metamorphism, which would have obliterated any fragile microfossils contained therein. It is therefore necessary to search for geochemical evidence of past biotic activity that has been preserved within miner als that are resistant to metamorphism. Here we report ion-microprobe measurements of the carbon-isotope composition of carbonaceous inclusi ons within grains of apatite (basic calcium phosphate) from the oldest known sediment sequences-a similar to 3,800-Myr-old banded iron forma tion from the Isua supracrustal belt, West Greenland(35), and a simila r formation from the nearby Akilia island that is possibly older than 3,850 Myr (ref, 3). The carbon in the carbonaceous inclusions is isoto pically light, indicative of biological activity; no known abiotic pro cess can explain the data. Unless some unknown abiotic process exists which is able both to create such isotopically light carbon and then s electively incorporate it into apatite grains, our results provide evi dence for the emergence of life on Earth by at least 3,800 Myr before present.