Archean molecular fossils and the early rise of eukaryotes.

Entrez PubMed: "Molecular fossils of biological lipids are preserved in 2700-million-year-old shales from the Pilbara Craton, Australia. Sequential extraction of adjacent samples shows that these hydrocarbon biomarkers are indigenous and syngenetic to the Archean shales, greatly extending the known geological range of such molecules. The presence of abundant 2alpha-methylhopanes, which are characteristic of cyanobacteria, indicates that oxygenic photosynthesis evolved well before the atmosphere became oxidizing. The presence of steranes, particularly cholestane and its 28- to 30-carbon analogs, provides persuasive evidence for the existence of eukaryotes 500 million to 1 billion years before the extant fossil record indicates that the lineage arose."

Archean molecular fossils and the early rise of eukaryotes. Brocks JJ, Logan GA, Buick R, Summons RE. Science. 1999 Aug 13;285(5430):1033-6.
Comment on: Science. 1999 Aug 13;285(5430):1025-6.