Earliest known life forms
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The earliest known life forms on Earth may be as old as 4.1 billion years (or Ga) according to biologically fractionated graphite inside a single zircon grain in the Jack Hills range of Australia.[2] The earliest evidence of life found in a stratigraphic unit, not just a single mineral grain, is the 3.7 Ga metasedimentary rocks containing graphite from the Isua Supracrustal Belt in Greenland.[3] The earliest direct known life on Earth are stromatolite fossils which have been found in 3.480-billion-year-old geyserite uncovered in the Dresser Formation of the Pilbara Craton of Western Australia.[4] Various microfossils of microorganisms have been found in 3.4 Ga rocks, including 3.465-billion-year-old Apex chert rocks from the same Australian craton region,[5] and in 3.42 Ga hydrothermal vent precipitates from Barberton, South Africa.[1] Much later in the geologic record, likely starting in 1.73 Ga, preserved molecular compounds of biologic origin are indicative of aerobic life.[6] Therefore, the earliest time for the origin of life on Earth is at least 3.5 billion years ago and possibly as early as 4.1 billion years ago — not long after the oceans formed 4.5 billion years ago and after the formation of the Earth 4.54 billion years ago.[7]
- ^ a b Cavalazzi, Barbara; et al. (14 July 2021). "Cellular remains in a ~3.42-billion-year-old subseafloor hydrothermal environment". Science Advances. 7 (9): eabf3963. Bibcode:2021SciA....7.3963C. doi:10.1126/sciadv.abf3963. PMC 8279515. PMID 34261651.
{{cite journal}}: CS1 maint: article number as page number (link) - ^ Bell, Elizabeth; Boehnke, Patrick; Harrison, T. Mark; Mao, Wendy L. (24 November 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon". Proceedings of the National Academy of Sciences of the United States of America. 112 (47): 14518–21. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. PMC 4664351. PMID 26483481.
- ^ Ohtomo, Yoko; Kakegawa, Takeshi; Ishida, Akizumi; et al. (January 2014). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience. 7 (1): 25–28. Bibcode:2014NatGe...7...25O. doi:10.1038/ngeo2025. ISSN 1752-0894. S2CID 54767854.
- ^ Noffke, Nora; Christian, Daniel; Wacey, David; Hazen, Robert M. (16 November 2013). "Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia". Astrobiology. 13 (12): 1103–24. Bibcode:2013AsBio..13.1103N. doi:10.1089/ast.2013.1030. ISSN 1531-1074. PMC 3870916. PMID 24205812.
- ^ Cite error: The named reference
PNAS-2017was invoked but never defined (see the help page). - ^ Hallmann, Christian; French, Katherine L.; Brocks, Jochen J. (2022-04-01). "Biomarkers in the Precambrian: Earth's Ancient Sedimentary Record of Life". Elements. 18 (2): 93–99. Bibcode:2022Eleme..18...93H. doi:10.2138/gselements.18.2.93. ISSN 1811-5217. S2CID 253517035.
- ^ "Age of the Earth". United States Geological Survey. 9 July 2007. Retrieved 2006-01-10.