Archean Molecular Fossils and the Early Rise of Eukaryotes

In the citing paper

“Until recently the earliest organic biomarker evidence for eukaryotic sterol synthesis was dated to 2.7 Ga (Brocks et al., 1999), but those records have now been convincingly tied to contamination (French et al., 2015).”

In the citing paper

“However, the chemical breakdown (diagenesis) of some biomolecules produces recognizable compounds that are preserved long-term. These breakdown products are often dubbed “molecular fossils” (Brocks et al., 1999; Summons et al., 1999).”

In the citing paper

“It is stratigraphically equivalent to WRL-1, which was the subject of the first report, to our knowledge, of Archean biomarkers for cyanobacteria and eukaryotes (1).”

In the citing paper

“Moreover, extractable acyclic isoprenoids and a homologous series of extractable n-alkanes (C 10-23+ ), both of which were prominent in previous Archean biomarker studies (1-3, 5, 7, 22, 23), were also below detection limits or cumulative laboratory blank concentrations in the AIDP samples.”

In the citing paper

“According to currently available H/C ratios and other indicators of thermal history, the metamorphic grades of AIDP-2 and AIDP-3 are similar to (1-4, 6, 7, 15, 21, 26) or lower than (5,22,23) the metamorphic grades of the rocks from which biomarkers have been previously reported.”

In the citing paper

“Consistent with earlier work (1,10,39,40), the bulk organic carbon was found to be anomalously 13 C-depleted, with δ 13 C values ranging from -32‰ to -50‰ (Fig. 2 and SI Appendix, Table S5).”

In the citing paper

“The spatial distribution of AIDP-2 and AIDP-3 geographically brackets and nearly spans the entire stratigraphic section from which all of the other Pilbara biomarkers have been previously reported (1,3,4,21).”

In the citing paper

“the analyses of the saw blade (before it was heat treated) and the sawed surfaces of the RHDH2A quarter-core highlight that sawing can contribute significant but variable hydrocarbon contaminants to the substrate, yet the cumulative blanks reported in previous studies did not record the hydrocarbon contribution from sawing (1,4,6,7).”

In the citing paper

“The HyPy hydrocarbon δ 13 C values reported here are, to our knowledge, the first compound-specific isotopic measurements that are in agreement with the strongly 13 C-depleted kerogens (δ 13 C bulk < -39‰) of the Neoarchean (1,10,39,40).”