Uncovering Ancient DNA in Petroleum: Insights into Earth Hidden Life Events and Geological History
Specific macromolecules in petroleum, preserved through geological processes from ancient organisms, are recognized as molecular fossils or geochemical markers (GMs). Our selected GMs indicate that the source rocks of Nanyang Oilfield formed in an anoxic, saline, and stratified lacustrine environment with marine influence. Contrary to science fiction notions that oil originates from ancient large animals, mainstream academia has consistently asserted that oil is derived from the organic matter of lower life forms, formed over extended geological processes, with intact DNA no longer persisting in oil post-formation. However, this study successfully extracted 3,159,020 DNA fragments from the petroleum samples using the nanoparticle affinity bead technology, followed by sequencing and classification via the mega screen method. These fragments, categorized as original in situ DNA (oriDNA), recent environmental DNA (preDNA), and paleo-environmental DNA (paeDNA), exhibit a "Genome Accumulated over Time" (GAT) pattern of "old-less, new-many". This aligns with findings from GMs while offering more specific genetic information. The analysis reveals evidence of historical events, including animal extinctions, marine invasions, ancient bird species presence, Asian Homo erectus activities, and modern human influences in preDNA. Notably, the mitogenomic data positions Asian Homo erectus closer to modern humans than to chimpanzees at the maternal basis. The absence of deamination in petroleum ancient DNA (aDNA) fragments is likely due to the anaerobic, anhydrous environment and the screening process that excludes degraded fragments. Consequently, the authenticity criteria and scope of application of traditional aDNA methods require reevaluation. Surprisingly, the near-absence of oriDNA has impeded our efforts to determine the specific biological origins of the oil. These findings position petroleum as a novel, non-skeletal source of aDNA, offering insights into ancient animal activities, geological changes, and human origins while underscoring its potential as an untapped resource for studying genetic preservation across geological timescales.