Earliest known life forms

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Evidence of possibly the oldest forms of life on Earth has been found in hydrothermal vent precipitates.[1][2]

The earliest known life forms on Earth are believed to be fossilized microorganisms found in hydrothermal vent precipitates, considered to be about 3.42 billion years old. The earliest time for the origin of life on Earth is at least 3.77 billion years ago, possibly as early as 4.28 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. The earliest direct known life on land may be stromatolites which have been found in 3.480-billion-year-old geyserite uncovered in the Dresser Formation of the Pilbara Craton of Western Australia and, as well, microfossils of microorganisms permineralized in 3.465-billion-year-old Apex chert rocks from the same Australian craton region.


Currently, the total number of living cells on the Earth is estimated to be 1030; the total number since the beginning of Earth, as 1040, and the total number for the entire time of a habitable planet Earth as 1041.[3][4] This is much larger than the total number of estimated stars (and Earth-like planets) in the observable universe as 1024, a number which is more than all the grains of beach sand on planet Earth;[5][6][7][8] but less than the total number of atoms estimated in the observable universe as 1082;[9] and the estimated total number of stars in an inflationary universe (observed and unobserved), as 10100.[10]

Earth remains the only place in the universe known to harbor life.[11][12] The origin of life on Earth was at least 3.77 billion years ago, possibly as early as 4.28–4.45 billion years ago.[2][13][14] The Earth's biosphere extends down to at least 19 km (12 mi) below the surface,[15][better source needed] and up to at least 76 km (47 mi)[16] into the atmosphere,[17][18][19] and includes soil, hydrothermal vents, and rock.[20][21] Further, the biosphere has been found to extend at least 914.4 m (3,000 ft; 0.5682 mi) below the ice of Antarctica,[22][23] and includes the deepest parts of the ocean,[24][25] down to rocks kilometers below the sea floor.[24][26][27] In July 2020, marine biologists reported that aerobic microorganisms (mainly), in "quasi-suspended animation", were found in organically-poor sediments, up to 101.5 million years old, 76.2 m (250 ft) below the seafloor in the South Pacific Gyre (SPG) ("the deadest spot in the ocean"), and could be the longest-living life forms ever found.[28] Under certain test conditions, life forms have been observed to survive in the vacuum of outer space.[29][30] More recently, in August 2020, bacteria were found to survive for three years in outer space, according to studies conducted on the International Space Station.[31] In February 2023, findings of a "dark microbiome" of unfamiliar microorganisms in the Atacama Desert in Chile, a Mars-like region of planet Earth, were reported.[32] The total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon.[33] According to one researcher, "You can find microbes everywhere – [they are] extremely adaptable to conditions, and survive wherever they are."[24]

Of all species of life forms that ever lived on Earth, over five billion,[34] more than 99% are estimated to be extinct.[35][36] Some estimates on the number of Earth's current species range from 10 million to 14 million,[37] of which about 1.2 million have been documented and over 86 percent remain undescribed.[38] However, a May 2016 scientific report estimates 1 trillion species currently on Earth, with only one-thousandth of one percent described.[39] Additionally, there are an estimated 10 nonillion (1031) individual viruses (including the related virions) on Earth, the most numerous type of biological entity,[40] which some biologists consider to be life forms.[41]

Fossil evidence[edit]

Archaea (prokaryotic microbes) were first found in extreme environments, such as hydrothermal vents.

The age of Earth is about 4.54 billion years;[42][43][44] the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago.[45] Some computer models suggest life began as early as 4.5 billion years ago.[13][14]

3.465-billion-year-old Australian Apex chert rocks may once have contained microorganisms, the earliest fossil evidence of life on Earth,[46][47] although the validity of these findings has been contested.[48] Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia.[49][50] Evidence of biogenic graphite,[51][52] and possibly stromatolites,[53][54][55] were discovered in 3.7 billion-year-old metasedimentary rocks in southwestern Greenland. Potential "remains of life" were found in 4.1 billion-year-old rocks in Western Australia.[56] "Putative filamentous microfossils", possibly of methanogens and/or methanotrophs, that lived about 3.42-billion-year-old in "a paleo-subseafloor hydrothermal vein system of the Barberton greenstone belt, have been identified in South Africa."[1]

The theory of panspermia speculates that life on Earth may have come from biological matter carried by space dust[57] or meteorites.[58]

Fossilized microorganisms (microfossils) have been found in hydrothermal vent precipitates from an ancient sea-bed in the Nuvvuagittuq Belt of Quebec, Canada. These may be as old as 4.28 billion years, the oldest evidence of life on Earth, suggesting "an almost instantaneous emergence of life" after ocean formation 4.41 billion years ago.[2] Some researchers even speculate that life may have started nearly 4.5 billion years ago.[13][14] According to biologist Stephen Blair Hedges, "If life arose relatively quickly on Earth ... then it could be common in the universe".[59][60][61] The possibility that terrestrial life forms may have been seeded from outer space has been considered.[62][63] In January 2018, a study found that 4.5 billion-year-old meteorites found on Earth contained liquid water along with prebiotic complex organic substances that may be ingredients for life.[58]

As for life on land, in 2019 scientists reported the discovery of a fossilized fungus, named Ourasphaira giraldae, in the Canadian Arctic, that may have grown on land a billion years ago, well before plants are thought to have been living on land.[64][65][66] In July 2018, scientists reported that the earliest life on land may have been bacteria 3.22 billion years ago.[67] In May 2017, evidence of microbial life on land may have been found in 3.48 billion-year-old geyserite in the Pilbara Craton of Western Australia.[68][69]

Genomic evidence[edit]

By comparing the genomes of modern organisms (in the domains Bacteria and Archaea), it is evident that there was a last universal common ancestor (LUCA). In 2016, M. C. Weiss and colleagues proposed a minimal set of genes that each occurred in at least two groups of Bacteria and two groups of Archaea. They argued that such a distribution of genes would be unlikely to arise by horizontal gene transfer, and so any such genes must have derived from the LUCA.[70] A molecular clock model suggests that the LUCA may have lived 4.477—4.519 billion years ago, within the Hadean eon.[13][14][a]


Earliest known life forms

See also[edit]


  1. ^ LUCA is not thought to be the first life on Earth, but rather the only type of organism of its time to still have living descendants.


  1. ^ 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.
  2. ^ a b c Dodd, Matthew S.; Papineau, Dominic; Grenne, Tor; slack, John F.; Rittner, Martin; Pirajno, Franco; O'Neil, Jonathan; Little, Crispin T. S. (2 March 2017). "Evidence for early life in Earth's oldest hydrothermal vent precipitates" (PDF). Nature. 543 (7643): 60–64. Bibcode:2017Natur.543...60D. doi:10.1038/nature21377. PMID 28252057. S2CID 2420384.
  3. ^ Overbye, Dennis (1 December 2023). "Exactly How Much Life Is on Earth? - According to a new study, living cells outnumber stars in the universe, highlighting the deep, underrated link between geophysics and biology". The New York Times. Archived from the original on 1 December 2023. Retrieved 1 December 2023.
  4. ^ Crockford, Peter W.. The geologic history of primary productivity. Current Biology. 6 November 2023 [Retrieved 1 December 2023];33(21):P7741-4750.E5.
  5. ^ Staff (2020). "How many stars are there in the Universe?". European Space Agency. Archived from the original on 17 January 2020. Retrieved January 17, 2020.
  6. ^ Mackie, Glen (1 February 2002). "To see the Universe in a Grain of Taranaki Sand". Swinburne University of Technology. Archived from the original on 28 December 2022. Retrieved 1 December 2023.
  7. ^ Mack, Eric (19 March 2015). "There may be more Earth-like planets than grains of sand on all our beaches - New research contends that the Milky Way alone is flush with billions of potentially habitable planets -- and that's just one sliver of the universe". CNET. Archived from the original on 1 December 2023. Retrieved 1 December 2023.
  8. ^ T. Bovaird, T.; Lineweaver, C.H.; Jacobsen, S.K. (13 March 2015). "Using the inclinations of Kepler systems to prioritize new Titius–Bode-based exoplanet predictions". Monthly Notices of the Royal Astronomical Society. 448 (4): 3608–3627. doi:10.1093/mnras/stv221. Archived from the original on 1 December 2023. Retrieved 1 December 2023.
  9. ^ Baker, Harry (11 July 2021). "How many atoms are in the observable universe?". Live Science. Archived from the original on 1 December 2023. Retrieved 1 December 2023.
  10. ^ Totani, Tomonori (3 February 2020). "Emergence of life in an inflationary universe". Scientific Reports. 10 (1671). doi:10.1038/s41598-020-58060-0. Archived from the original on 1 December 2023. Retrieved 1 December 2023.
  11. ^ Graham, Robert W. (February 1990). "Extraterrestrial Life in the Universe" (PDF). NASA (NASA Technical Memorandum 102363). Lewis Research Center, Cleveland, Ohio. Retrieved 2 June 2015.
  12. ^ Altermann, Wladyslaw (2009). "From Fossils to Astrobiology – A Roadmap to Fata Morgana?". In Seckbach, Joseph; Walsh, Maud (eds.). From Fossils to Astrobiology: Records of Life on Earth and the Search for Extraterrestrial Biosignatures. Cellular Origin, Life in Extreme Habitats and Astrobiology. Vol. 12. Dordrecht, the Netherlands; London: Springer Science+Business Media. p. xvii. ISBN 978-1-4020-8836-0. LCCN 2008933212.
  13. ^ a b c d Staff (20 August 2018). "A timescale for the origin and evolution of all of life on Earth". Phys.org. Retrieved 20 August 2018.
  14. ^ a b c d Betts, Holly C.; Putick, Mark N.; Clark, James W.; Williams, Tom A.; Donoghue, Philip C.J.; Pisani, Davide (20 August 2018). "Integrated genomic and fossil evidence illuminates life's early evolution and eukaryote origin". Nature. 2 (10): 1556–1562. doi:10.1038/s41559-018-0644-x. PMC 6152910. PMID 30127539.
  15. ^ Klein, JoAnna (19 December 2018). "Deep Beneath Your Feet, They Live in the Octillions – The real journey to the center of the Earth has begun, and scientists are discovering subsurface microbial beings that shake up what we think we know about life". The New York Times. Retrieved 21 December 2018.
  16. ^ Loeb, Abraham (4 November 2019). "Did Life from Earth Escape the Solar System Eons Ago?". Scientific American. Retrieved 5 November 2019.
  17. ^ University of Georgia (25 August 1998). "First-Ever Scientific Estimate Of Total Bacteria On Earth Shows Far Greater Numbers Than Ever Known Before". Science Daily. Retrieved 10 November 2014.
  18. ^ Hadhazy, Adam (12 January 2015). "Life Might Thrive a Dozen Miles Beneath Earth's Surface". Astrobiology Magazine. Archived from the original on 2020-11-02. Retrieved 11 March 2017.{{cite web}}: CS1 maint: unfit URL (link)
  19. ^ Fox-Skelly, Jasmin (24 November 2015). "The Strange Beasts That Live In Solid Rock Deep Underground". BBC online. Retrieved 11 March 2017.
  20. ^ Suzuki, Yohey; et al. (2 April 2020). "Deep microbial proliferation at the basalt interface in 33.5–104 million-year-old oceanic crust". Communications Biology. 3 (136): 136. doi:10.1038/s42003-020-0860-1. PMC 7118141. PMID 32242062.
  21. ^ University of Tokyo (2 April 2020). "Discovery of life in solid rock deep beneath sea may inspire new search for life on Mars – Bacteria live in tiny clay-filled cracks in solid rock millions of years old". EurekAlert!. Retrieved 2 April 2020.
  22. ^ Griffiths, Huw J.; et al. (15 February 2021). "Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Beneath an Antarctic Ice Shelf". Frontiers in Marine Science. 8. doi:10.3389/fmars.2021.642040.
  23. ^ Fox, Douglas (20 August 2014). "Lakes under the ice: Antarctica's secret garden". Nature. 512 (7514): 244–246. Bibcode:2014Natur.512..244F. doi:10.1038/512244a. PMID 25143097.
  24. ^ a b c Choi, Charles Q. (17 March 2013). "Microbes Thrive in Deepest Spot on Earth". LiveScience. Retrieved 17 March 2013.
  25. ^ Glud, Ronnie; Wenzhöfer, Frank; Middelboe, Mathias; Oguri, Kazumasa; Turnewitsch, Robert; Canfield, Donald E.; Kitazato, Hiroshi (17 March 2013). "High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth". Nature Geoscience. 6 (4): 284–288. Bibcode:2013NatGe...6..284G. doi:10.1038/ngeo1773.
  26. ^ Oskin, Becky (14 March 2013). "Intraterrestrials: Life Thrives in Ocean Floor". LiveScience. Retrieved 17 March 2013.
  27. ^ Morelle, Rebecca (15 December 2014). "Microbes discovered by deepest marine drill analysed". BBC News. Retrieved 15 December 2014.
  28. ^ Morono, Yuki; et al. (28 July 2020). "Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years". Nature Communications. 11 (3626): 3626. Bibcode:2020NatCo..11.3626M. doi:10.1038/s41467-020-17330-1. PMC 7387439. PMID 32724059.
  29. ^ Dose, K.; Bieger-Dose, A.; Dillmann, R.; Gill, M.; Kerz, O.; Klein, A.; Meinert, H.; Nawroth, T.; Risi, S.; Stridde, C. (1995). "ERA-experiment "space biochemistry"". Advances in Space Research. 16 (8): 119–129. Bibcode:1995AdSpR..16h.119D. doi:10.1016/0273-1177(95)00280-R. PMID 11542696.
  30. ^ Horneck, G.; Eschweiler, U.; Reitz, G.; Wehner, J.; Willimek, R.; Strauch, K. (1995). "Biological responses to space: results of the experiment "Exobiological Unit" of ERA on EURECA I". Adv. Space Res. 16 (8): 105–118. Bibcode:1995AdSpR..16h.105H. doi:10.1016/0273-1177(95)00279-N. PMID 11542695.
  31. ^ Kawaguchi, Yuko; et al. (26 August 2020). "DNA Damage and Survival Time Course of Deinococcal Cell Pellets During 3 Years of Exposure to Outer Space". Frontiers in Microbiology. 11: 2050. doi:10.3389/fmicb.2020.02050. PMC 7479814. PMID 32983036. S2CID 221300151.
  32. ^ Azua-Bustos, Armando; et al. (21 February 2023). "Dark microbiome and extremely low organics in Atacama fossil delta unveil Mars life detection limits". Nature Communications. 14 (808): 808. doi:10.1038/s41467-023-36172-1. PMC 9944251. PMID 36810853.
  33. ^ "The Biosphere: Diversity of Life". Aspen Global Change Institute. Basalt, CO. Archived from the original on 2 September 2010. Retrieved 19 July 2015.
  34. ^ Kunin, W.E.; Gaston, Kevin, eds. (1996). The Biology of Rarity: Causes and consequences of rare – common differences. Springer. ISBN 978-0-412-63380-5. Retrieved 26 May 2015.
  35. ^ Stearns, Beverly Peterson; Stearns, S. C.; Stearns, Stephen C. (2000). Watching, from the Edge of Extinction. Yale University Press. p. preface x. ISBN 978-0-300-08469-6. Retrieved 30 May 2017.
  36. ^ Novacek, Michael J. (8 November 2014). "Prehistory's Brilliant Future". The New York Times. Retrieved 25 December 2014.
  37. ^ G. Miller; Scott Spoolman (2012). Environmental Science – Biodiversity Is a Crucial Part of the Earth's Natural Capital. Cengage Learning. p. 62. ISBN 978-1-133-70787-5. Retrieved 27 December 2014.
  38. ^ Mora, C.; Tittensor, D.P.; Adl, S.; Simpson, A.G.; Worm, B. (23 August 2011). "How many species are there on Earth and in the ocean?". PLOS Biology. 9 (8): e1001127. doi:10.1371/journal.pbio.1001127. PMC 3160336. PMID 21886479.
  39. ^ Staff (2 May 2016). "Researchers find that Earth may be home to 1 trillion species". National Science Foundation. Retrieved 6 May 2016.
  40. ^ Edwards RA, Rohwer F (June 2005). "Viral metagenomics". Nature Reviews Microbiology. 3 (6): 504–10. doi:10.1038/nrmicro1163. PMID 15886693. S2CID 8059643.
  41. ^ Villarreal, Luis P. (8 August 2008). "Are Viruses Alive? - Although viruses challenge our concept of what "living" means, they are vital members of the web of life". Scientific American. Retrieved 19 May 2020.
  42. ^ "Age of the Earth". United States Geological Survey. 9 July 2007. Retrieved 2006-01-10.
  43. ^ Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London. 190 (1): 205–221. Bibcode:2001GSLSP.190..205D. doi:10.1144/GSL.SP.2001.190.01.14. S2CID 130092094.
  44. ^ Manhesa, Gérard; Allègre, Claude J.; Dupréa, Bernard; Hamelin, Bruno (May 1980). "Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics". Earth and Planetary Science Letters. 47 (3): 370–382. Bibcode:1980E&PSL..47..370M. doi:10.1016/0012-821X(80)90024-2. ISSN 0012-821X.
  45. ^ Multiple Sources:
  46. ^ Tyrell, Kelly April (18 December 2017). "Oldest fossils ever found show life on Earth began before 3.5 billion years ago". University of Wisconsin–Madison. Retrieved 18 December 2017.
  47. ^ Schopf, J. William; Kitajima, Kouki; Spicuzza, Michael J.; Kudryavtsev, Anatolly B.; Valley, John W. (2017). "SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions". PNAS. 115 (1): 53–58. Bibcode:2018PNAS..115...53S. doi:10.1073/pnas.1718063115. PMC 5776830. PMID 29255053.
  48. ^ Brasier, Martin D.; Green, Owen R.; Lindsay, John F.; McLoughlin, Nicola; Steele, Andrew; Stoakes, Cris (2005-10-21). "Critical testing of Earth's oldest putative fossil assemblage from the ~3.5Ga Apex chert, Chinaman Creek, Western Australia". Precambrian Research. 140 (1): 55–102. doi:10.1016/j.precamres.2005.06.008. ISSN 0301-9268.
  49. ^ 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): 1103–1124. Bibcode:2013AsBio..13.1103N. doi:10.1089/ast.2013.1030. ISSN 1531-1074. PMC 3870916. PMID 24205812.
  50. ^ Djokic, Tara; Van Kranendonk, Martin J.; Campbell, Kathleen A.; Walter, Malcolm R.; Ward, Colin R. (9 May 2017). "Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits". Nature Communications. 8: 15263. Bibcode:2017NatCo...815263D. doi:10.1038/ncomms15263. PMC 5436104. PMID 28486437.
  51. ^ 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.
  52. ^ Hassenkam, T.; Rosing, M. T. (2017-11-02). "3.7 billion year old biogenic remains". Communicative & Integrative Biology. 10 (5–6): e1380759. doi:10.1080/19420889.2017.1380759. ISSN 1942-0889. PMC 5731516. PMID 29260796.
  53. ^ Wade, Nicholas (31 August 2016). "World's Oldest Fossils Found in Greenland". The New York Times. Retrieved 31 August 2016.
  54. ^ a b Allwood, Abigail C. (22 September 2016). "Evidence of life in Earth's oldest rocks". Nature. 537 (7621): 500–5021. doi:10.1038/nature19429. PMID 27580031. S2CID 205250633.
  55. ^ a b Wei-Haas, Maya (17 October 2018). "'World's oldest fossils' may just be pretty rocks – Analysis of 3.7-billion-year-old outcrops has reignited controversy over when life on Earth began". National Geographic. Archived from the original on October 17, 2018. Retrieved 19 October 2018.
  56. ^ 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): 14518–14521. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. PMC 4664351. PMID 26483481.
  57. ^ Berera, Arjun (6 November 2017). "Space dust collisions as a planetary escape mechanism". Astrobiology. 17 (12): 1274–1282. arXiv:1711.01895. Bibcode:2017AsBio..17.1274B. doi:10.1089/ast.2017.1662. PMID 29148823. S2CID 126012488.
  58. ^ a b Chan, Queenie H. S.; et al. (10 January 2018). "Organic matter in extraterrestrial water-bearing salt crystals". Science Advances. 4 (1, eaao3521): eaao3521. doi:10.1126/sciadv.aao3521. PMC 5770164. PMID 29349297.
  59. ^ Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Associated Press. Retrieved 9 October 2018.
  60. ^ Schouten, Lucy (20 October 2015). "When did life first emerge on Earth? Maybe a lot earlier than we thought". The Christian Science Monitor. Boston, Massachusetts: Christian Science Publishing Society. ISSN 0882-7729. Archived from the original on 22 March 2016. Retrieved 9 October 2018.
  61. ^ Johnston, Ian (2 October 2017). "Life first emerged in 'warm little ponds' almost as old as the Earth itself – Charles Darwin's famous idea backed by new scientific study". The Independent. Retrieved 2 October 2017.
  62. ^ Steele, Edward J.; et al. (1 August 2018). "Cause of Cambrian Explosion – Terrestrial or Cosmic?". Progress in Biophysics and Molecular Biology. 136: 3–23. doi:10.1016/j.pbiomolbio.2018.03.004. PMID 29544820. S2CID 4486796.
  63. ^ McRae, Mike (28 December 2021). "A Weird Paper Tests The Limits of Science by Claiming Octopuses Came From Space". ScienceAlert. Retrieved 29 December 2021.
  64. ^ Zimmer, Carl (22 May 2019). "How Did Life Arrive on Land? A Billion-Year-Old Fungus May Hold Clues – A cache of microscopic fossils from the Arctic hints that fungi reached land long before plants". The New York Times. Retrieved 23 May 2019.
  65. ^ Loron, Corentin C.; François, Camille; Rainbird, Robert H.; Turner, Elizabeth C.; Borensztajn, Stephan; Javaux, Emmanuelle J. (22 May 2019). "Early fungi from the Proterozoic era in Arctic Canada". Nature. Springer Science and Business Media LLC. 570 (7760): 232–235. Bibcode:2019Natur.570..232L. doi:10.1038/s41586-019-1217-0. ISSN 0028-0836. PMID 31118507. S2CID 162180486.
  66. ^ Timmer, John (22 May 2019). "Billion-year-old fossils may be early fungus". Ars Technica. Retrieved 23 May 2019.
  67. ^ Homann, Martin; et al. (23 July 2018). "Microbial life and biogeochemical cycling on land 3,220 million years ago" (PDF). Nature Geoscience. 11 (9): 665–671. Bibcode:2018NatGe..11..665H. doi:10.1038/s41561-018-0190-9. S2CID 134935568.
  68. ^ Staff (9 May 2017). "Oldest evidence of life on land found in 3.48-billion-year-old Australian rocks". Phys.org. Retrieved 13 May 2017.
  69. ^ University of New South Wales (26 September 2019). "Earliest signs of life: Scientists find microbial remains in ancient rocks". EurekAlert!. Retrieved 27 September 2019.
  70. ^ Weiss, M. C.; Sousa, F. L.; Mrnjavac, N.; Neukirchen, S.; Roettger, M.; Nelson-Sathi, S.; Martin, W. F. (2016). "The physiology and habitat of the last universal common ancestor". Nature Microbiology. 1 (9): 16116. doi:10.1038/nmicrobiol.2016.116. PMID 27562259. S2CID 2997255.
  71. ^ Porada H.; Ghergut J.; Bouougri El H. (2008). "Kinneyia-Type Wrinkle Structures – Critical Review And Model Of Formation". PALAIOS. 23 (2): 65–77. Bibcode:2008Palai..23...65P. doi:10.2110/palo.2006.p06-095r. S2CID 128464944.

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