This research paper describes findings from the oldest known rocks of marine sedimentary origin from the southwestern coast of Greenland. Evidence suggests that these rocks preserve a biogeochemical record of early life. On the basis of the age of these rocks, the emergence of the biosphere appears to overlap with a period of intense global bombardment. This finding could also be consistent with evidence from molecular biology that places the ancestry of primitive bacteria living in extreme thermal environments near the last common ancestor of all known life.
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