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{{further |Abiogenesis}}
{{further |Abiogenesis}}


Earth remains the only place in the [[universe]] known to harbor [[life]].<ref name="NASA-1990">{{cite journal |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900013148.pdf |title=Extraterrestrial Life in the Universe |last=Graham |first=Robert W. |date=February 1990 |place=[[Glenn Research Center |Lewis Research Center]], Cleveland, Ohio |website=[[NASA]] |type=NASA Technical Memorandum 102363 |access-date=2 June 2015}}</ref><ref name="Alterman-2009">{{cite book |last=Altermann |first=Wladyslaw |year=2009 |chapter=From Fossils to Astrobiology – A Roadmap to Fata Morgana? |editor1-last=Seckbach |editor1-first=Joseph |editor2-last=Walsh |editor2-first=Maud |title=From Fossils to Astrobiology: Records of Life on Earth and the Search for Extraterrestrial Biosignatures |series=Cellular Origin, Life in Extreme Habitats and Astrobiology |volume=12 |location=Dordrecht, the Netherlands; London |publisher=[[Springer Science+Business Media]] |isbn=978-1-4020-8836-0 |lccn=2008933212 |page=xvii}}</ref> The [[Abiogenesis |origin of life]] on Earth was at least 3.77 billion years ago, possibly as early as 4.28 billion years ago.<ref name="NAT-20170301" /><ref name="PHY-20180820" /><ref name="NAT-20180820" /> The Earth's [[biosphere]] extends down to at least {{convert |12 |mi |km |order=flip |abbr=on}} below the surface,<ref name="NYT-20181219">{{cite news |url=https://www.nytimes.com/2018/12/19/science/subsurface-microbes.html |title=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. |last=Klein |first=JoAnna |date=19 December 2018 |work=[[The New York Times]] |access-date=21 December 2018}}</ref>{{better source needed |date=October 2023 |reason=Multiple news reports; better would be a scientific source here}} and up to at least {{convert |47 |mi |km |order=flip |abbr=on}}<ref name="SA-20191104">{{cite news |last=Loeb |first=Abraham |author-link=Abraham Loeb |title=Did Life from Earth Escape the Solar System Eons Ago? |url=https://blogs.scientificamerican.com/observations/did-life-from-earth-escape-the-solar-system-eons-ago/ |date=4 November 2019 |work=[[Scientific American]] |access-date=5 November 2019 }}</ref> into the [[Atmosphere of Earth |atmosphere]],<ref name="SD-19980625-UG">{{cite web |url=https://www.sciencedaily.com/releases/1998/08/980825080732.htm |title=First-Ever Scientific Estimate Of Total Bacteria On Earth Shows Far Greater Numbers Than Ever Known Before |author=University of Georgia |date=25 August 1998 |work=[[Science Daily]] |access-date=10 November 2014}}</ref><ref name="ABM-20150112">{{cite web |url=http://www.astrobio.net/extreme-life/life-might-thrive-dozen-miles-beneath-earths-surface/ |title=Life Might Thrive a Dozen Miles Beneath Earth's Surface |last=Hadhazy |first=Adam |date=12 January 2015 |work=[[Astrobiology Magazine]] |access-date=11 March 2017 |archive-url=https://web.archive.org/web/20201102170152/https://www.astrobio.net/extreme-life/life-might-thrive-dozen-miles-beneath-earths-surface/ |archive-date=2020-11-02 |url-status=usurped}}</ref><ref name="BBC-20151124">{{cite web |url=http://www.bbc.com/earth/story/20151124-meet-the-strange-creatures-that-live-in-solid-rock-deep-underground |title=The Strange Beasts That Live In Solid Rock Deep Underground |last=Fox-Skelly |first=Jasmin |date=24 November 2015 |work=[[BBC online]] |access-date=11 March 2017}}</ref> and includes [[pedosphere |soil]], [[Hydrothermal vent#Biological communities |hydrothermal vents]], and [[endolith |rock]].<ref name="NC-20200402">{{cite journal |author=Suzuki, Yohey |display-authors=et al. |title=Deep microbial proliferation at the basalt interface in 33.5–104 million-year-old oceanic crust |date=2 April 2020 |journal=[[Communications Biology]] |volume=3 |issue=136 |page=136 |doi=10.1038/s42003-020-0860-1 |pmid=32242062 |pmc=7118141 |doi-access=free }}</ref><ref name="EA-20200402">{{cite news |author=[[University of Tokyo]] |title=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 |url=https://www.eurekalert.org/pub_releases/2020-04/uot-dol033020.php |date=2 April 2020 |work=[[EurekAlert!]] |access-date=2 April 2020 }}</ref> Further, the biosphere has been found to extend at least {{convert |914.4 |m |ft mi |abbr=on}} below the ice of [[Antarctica]],<ref name="FR-20210215">{{cite journal |author=Griffiths, Huw J. |display-authors=et al. |title=Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Beneath an Antarctic Ice Shelf |date=15 February 2021 |journal=[[Frontiers in Marine Science]] |volume=8 |doi=10.3389/fmars.2021.642040 |doi-access=free }}</ref><ref name="NAT-20140820">{{cite journal |last=Fox |first=Douglas |date=20 August 2014 |title=Lakes under the ice: Antarctica's secret garden |journal=[[Nature (journal) |Nature]] |volume=512 |issue=7514 |pages=244–246 |bibcode=2014Natur.512..244F |doi=10.1038/512244a |pmid=25143097 |doi-access=free}}</ref> and includes the [[Deep sea#Biology |deepest parts of the ocean]],<ref name="LS-20130317">{{cite web |url=http://www.livescience.com/27954-microbes-mariana-trench.html |title=Microbes Thrive in Deepest Spot on Earth |last=Choi |first=Charles Q. |date=17 March 2013 |website=[[LiveScience]] |access-date=17 March 2013}}</ref><ref name="NG-20130317">{{cite journal |last1=Glud |first1=Ronnie |last2=Wenzhöfer |first2=Frank |last3=Middelboe |first3=Mathias |last4=Oguri |first4=Kazumasa |last5=Turnewitsch |first5=Robert |last6=Canfield |first6=Donald E. |last7=Kitazato |first7=Hiroshi |date=17 March 2013 |title=High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth |journal=[[Nature Geoscience]] |volume=6 |issue=4 |pages=284–288 |bibcode=2013NatGe...6..284G |doi=10.1038/ngeo1773}}</ref> down to rocks kilometers below the sea floor.<ref name="LS-20130317" /><ref name="LS-20130314">{{cite web |url=http://www.livescience.com/27899-ocean-subsurface-ecosystem-found.html |title=Intraterrestrials: Life Thrives in Ocean Floor |last=Oskin |first=Becky |date=14 March 2013 |website=[[LiveScience]] |access-date=17 March 2013}}</ref><ref name="BBC-20141215-RM">{{cite news |url=https://www.bbc.com/news/science-environment-30489814 |title=Microbes discovered by deepest marine drill analysed |last=Morelle |first=Rebecca |author-link=Rebecca Morelle |date=15 December 2014 |work=[[BBC News]] |access-date=15 December 2014}}</ref> In July 2020, [[Marine biology |marine biologists]] reported that [[Aerobic organism |aerobic]] [[microorganism]]s (mainly), in "[[Suspended animation |quasi-suspended animation]]", were found in [[Sediment |organically-poor sediments]], up to 101.5 million years old, {{convert |76.2 |m |ft |abbr=on}} below the [[Seabed |seafloor]] in the [[South Pacific Gyre]] (SPG) ("the deadest spot in the ocean"), and could be the [[List of longest-living organisms |longest-living life forms]] ever found.<ref name="NC-20200728">{{cite journal |author=Morono, Yuki |display-authors=et al. |title=Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years |date=28 July 2020 |journal=[[Nature Communications]] |volume=11 |number=3626 |page=3626 |doi=10.1038/s41467-020-17330-1 |pmid=32724059 |pmc=7387439 |bibcode=2020NatCo..11.3626M }}</ref> Under certain test conditions, life forms have been observed to [[Panspermia#Research in outer space |survive in the vacuum of outer space]].<ref name="Dose">{{cite journal |last1=Dose |first1=K. |last2=Bieger-Dose |first2=A. |last3=Dillmann |first3=R. |last4=Gill |first4=M. |last5=Kerz |first5=O. |last6=Klein |first6=A. |last7=Meinert |first7=H. |last8=Nawroth |first8=T. |last9=Risi |first9=S. |year=1995 |title=ERA-experiment "space biochemistry" |journal=Advances in Space Research |volume=16 |issue=8 |pages=119–129 |bibcode=1995AdSpR..16h.119D |doi=10.1016/0273-1177(95)00280-R |pmid=11542696 |last10=Stridde |first10=C.}}</ref><ref name="Horneck">{{cite journal |last1=Horneck |first1=G. |author2=Eschweiler, U. |author3=Reitz, G. |author4=Wehner, J. |author5=Willimek, R. |author6=Strauch, K. |year=1995 |title=Biological responses to space: results of the experiment "Exobiological Unit" of ERA on EURECA I |journal=Adv. Space Res. |volume=16 |issue=8 |pages=105–118 |bibcode=1995AdSpR..16h.105H |doi=10.1016/0273-1177(95)00279-N |pmid=11542695}}</ref> 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]].<ref name="FM-20200826">{{cite journal |author=Kawaguchi, Yuko |display-authors=et al. |title=DNA Damage and Survival Time Course of Deinococcal Cell Pellets During 3 Years of Exposure to Outer Space |date=26 August 2020 |journal=[[Frontiers in Microbiology]] |volume=11 |page=2050 |doi=10.3389/fmicb.2020.02050 |pmid=32983036 |pmc=7479814 |s2cid=221300151 |doi-access=free }}</ref> In February 2023, findings of a "[[dark microbiome]]" of unfamiliar [[microorganism]]s in the [[Atacama Desert]] in [[Chile]], a [[Mars]]-like region of planet [[Earth]], were reported.<ref name="NC-20230221">{{cite journal |author=Azua-Bustos, Armando |display-authors=et al. |title=Dark microbiome and extremely low organics in Atacama fossil delta unveil Mars life detection limits |date=21 February 2023 |journal=[[Nature Communications]] |volume=14 |issue=808 |page=808 |doi=10.1038/s41467-023-36172-1 |pmid=36810853 |pmc=9944251 }}</ref> The total mass of the [[biosphere]] has been estimated to be as much as 4 trillion tons of [[carbon]].<ref name="AGCI-2015">{{cite web |url=http://www.agci.org/classroom/biosphere/index.php |title=The Biosphere: Diversity of Life |author=<!--Staff writer(s); no by-line.--> |work=Aspen Global Change Institute |location=Basalt, CO |access-date=19 July 2015 |archive-date=2 September 2010 |archive-url=https://web.archive.org/web/20100902111048/http://www.agci.org/classroom/biosphere/index.php}}</ref> According to one researcher, "You can find [[microbe]]s everywhere – [they are] extremely adaptable to conditions, and survive wherever they are."<ref name="LS-20130317" />
Earth remains the only place in the [[universe]] known to harbor [[life]].<ref name="NASA-1990">{{cite journal |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900013148.pdf |title=Extraterrestrial Life in the Universe |last=Graham |first=Robert W. |date=February 1990 |place=[[Glenn Research Center |Lewis Research Center]], Cleveland, Ohio |website=[[NASA]] |type=NASA Technical Memorandum 102363 |access-date=2 June 2015}}</ref><ref name="Alterman-2009">{{cite book |last=Altermann |first=Wladyslaw |year=2009 |chapter=From Fossils to Astrobiology – A Roadmap to Fata Morgana? |editor1-last=Seckbach |editor1-first=Joseph |editor2-last=Walsh |editor2-first=Maud |title=From Fossils to Astrobiology: Records of Life on Earth and the Search for Extraterrestrial Biosignatures |series=Cellular Origin, Life in Extreme Habitats and Astrobiology |volume=12 |location=Dordrecht, the Netherlands; London |publisher=[[Springer Science+Business Media]] |isbn=978-1-4020-8836-0 |lccn=2008933212 |page=xvii}}</ref> The [[Abiogenesis |origin of life]] on Earth was at least 3.77 billion years ago, possibly as early as 4.28–4.5 billion years ago.<ref name="NAT-20170301" /><ref name="PHY-20180820" /><ref name="NAT-20180820" /> The Earth's [[biosphere]] extends down to at least {{convert |12 |mi |km |order=flip |abbr=on}} below the surface,<ref name="NYT-20181219">{{cite news |url=https://www.nytimes.com/2018/12/19/science/subsurface-microbes.html |title=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. |last=Klein |first=JoAnna |date=19 December 2018 |work=[[The New York Times]] |access-date=21 December 2018}}</ref>{{better source needed |date=October 2023 |reason=Multiple news reports; better would be a scientific source here}} and up to at least {{convert |47 |mi |km |order=flip |abbr=on}}<ref name="SA-20191104">{{cite news |last=Loeb |first=Abraham |author-link=Abraham Loeb |title=Did Life from Earth Escape the Solar System Eons Ago? |url=https://blogs.scientificamerican.com/observations/did-life-from-earth-escape-the-solar-system-eons-ago/ |date=4 November 2019 |work=[[Scientific American]] |access-date=5 November 2019 }}</ref> into the [[Atmosphere of Earth |atmosphere]],<ref name="SD-19980625-UG">{{cite web |url=https://www.sciencedaily.com/releases/1998/08/980825080732.htm |title=First-Ever Scientific Estimate Of Total Bacteria On Earth Shows Far Greater Numbers Than Ever Known Before |author=University of Georgia |date=25 August 1998 |work=[[Science Daily]] |access-date=10 November 2014}}</ref><ref name="ABM-20150112">{{cite web |url=http://www.astrobio.net/extreme-life/life-might-thrive-dozen-miles-beneath-earths-surface/ |title=Life Might Thrive a Dozen Miles Beneath Earth's Surface |last=Hadhazy |first=Adam |date=12 January 2015 |work=[[Astrobiology Magazine]] |access-date=11 March 2017 |archive-url=https://web.archive.org/web/20201102170152/https://www.astrobio.net/extreme-life/life-might-thrive-dozen-miles-beneath-earths-surface/ |archive-date=2020-11-02 |url-status=usurped}}</ref><ref name="BBC-20151124">{{cite web |url=http://www.bbc.com/earth/story/20151124-meet-the-strange-creatures-that-live-in-solid-rock-deep-underground |title=The Strange Beasts That Live In Solid Rock Deep Underground |last=Fox-Skelly |first=Jasmin |date=24 November 2015 |work=[[BBC online]] |access-date=11 March 2017}}</ref> and includes [[pedosphere |soil]], [[Hydrothermal vent#Biological communities |hydrothermal vents]], and [[endolith |rock]].<ref name="NC-20200402">{{cite journal |author=Suzuki, Yohey |display-authors=et al. |title=Deep microbial proliferation at the basalt interface in 33.5–104 million-year-old oceanic crust |date=2 April 2020 |journal=[[Communications Biology]] |volume=3 |issue=136 |page=136 |doi=10.1038/s42003-020-0860-1 |pmid=32242062 |pmc=7118141 |doi-access=free }}</ref><ref name="EA-20200402">{{cite news |author=[[University of Tokyo]] |title=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 |url=https://www.eurekalert.org/pub_releases/2020-04/uot-dol033020.php |date=2 April 2020 |work=[[EurekAlert!]] |access-date=2 April 2020 }}</ref> Further, the biosphere has been found to extend at least {{convert |914.4 |m |ft mi |abbr=on}} below the ice of [[Antarctica]],<ref name="FR-20210215">{{cite journal |author=Griffiths, Huw J. |display-authors=et al. |title=Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Beneath an Antarctic Ice Shelf |date=15 February 2021 |journal=[[Frontiers in Marine Science]] |volume=8 |doi=10.3389/fmars.2021.642040 |doi-access=free }}</ref><ref name="NAT-20140820">{{cite journal |last=Fox |first=Douglas |date=20 August 2014 |title=Lakes under the ice: Antarctica's secret garden |journal=[[Nature (journal) |Nature]] |volume=512 |issue=7514 |pages=244–246 |bibcode=2014Natur.512..244F |doi=10.1038/512244a |pmid=25143097 |doi-access=free}}</ref> and includes the [[Deep sea#Biology |deepest parts of the ocean]],<ref name="LS-20130317">{{cite web |url=http://www.livescience.com/27954-microbes-mariana-trench.html |title=Microbes Thrive in Deepest Spot on Earth |last=Choi |first=Charles Q. |date=17 March 2013 |website=[[LiveScience]] |access-date=17 March 2013}}</ref><ref name="NG-20130317">{{cite journal |last1=Glud |first1=Ronnie |last2=Wenzhöfer |first2=Frank |last3=Middelboe |first3=Mathias |last4=Oguri |first4=Kazumasa |last5=Turnewitsch |first5=Robert |last6=Canfield |first6=Donald E. |last7=Kitazato |first7=Hiroshi |date=17 March 2013 |title=High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth |journal=[[Nature Geoscience]] |volume=6 |issue=4 |pages=284–288 |bibcode=2013NatGe...6..284G |doi=10.1038/ngeo1773}}</ref> down to rocks kilometers below the sea floor.<ref name="LS-20130317" /><ref name="LS-20130314">{{cite web |url=http://www.livescience.com/27899-ocean-subsurface-ecosystem-found.html |title=Intraterrestrials: Life Thrives in Ocean Floor |last=Oskin |first=Becky |date=14 March 2013 |website=[[LiveScience]] |access-date=17 March 2013}}</ref><ref name="BBC-20141215-RM">{{cite news |url=https://www.bbc.com/news/science-environment-30489814 |title=Microbes discovered by deepest marine drill analysed |last=Morelle |first=Rebecca |author-link=Rebecca Morelle |date=15 December 2014 |work=[[BBC News]] |access-date=15 December 2014}}</ref> In July 2020, [[Marine biology |marine biologists]] reported that [[Aerobic organism |aerobic]] [[microorganism]]s (mainly), in "[[Suspended animation |quasi-suspended animation]]", were found in [[Sediment |organically-poor sediments]], up to 101.5 million years old, {{convert |76.2 |m |ft |abbr=on}} below the [[Seabed |seafloor]] in the [[South Pacific Gyre]] (SPG) ("the deadest spot in the ocean"), and could be the [[List of longest-living organisms |longest-living life forms]] ever found.<ref name="NC-20200728">{{cite journal |author=Morono, Yuki |display-authors=et al. |title=Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years |date=28 July 2020 |journal=[[Nature Communications]] |volume=11 |number=3626 |page=3626 |doi=10.1038/s41467-020-17330-1 |pmid=32724059 |pmc=7387439 |bibcode=2020NatCo..11.3626M }}</ref> Under certain test conditions, life forms have been observed to [[Panspermia#Research in outer space |survive in the vacuum of outer space]].<ref name="Dose">{{cite journal |last1=Dose |first1=K. |last2=Bieger-Dose |first2=A. |last3=Dillmann |first3=R. |last4=Gill |first4=M. |last5=Kerz |first5=O. |last6=Klein |first6=A. |last7=Meinert |first7=H. |last8=Nawroth |first8=T. |last9=Risi |first9=S. |year=1995 |title=ERA-experiment "space biochemistry" |journal=Advances in Space Research |volume=16 |issue=8 |pages=119–129 |bibcode=1995AdSpR..16h.119D |doi=10.1016/0273-1177(95)00280-R |pmid=11542696 |last10=Stridde |first10=C.}}</ref><ref name="Horneck">{{cite journal |last1=Horneck |first1=G. |author2=Eschweiler, U. |author3=Reitz, G. |author4=Wehner, J. |author5=Willimek, R. |author6=Strauch, K. |year=1995 |title=Biological responses to space: results of the experiment "Exobiological Unit" of ERA on EURECA I |journal=Adv. Space Res. |volume=16 |issue=8 |pages=105–118 |bibcode=1995AdSpR..16h.105H |doi=10.1016/0273-1177(95)00279-N |pmid=11542695}}</ref> 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]].<ref name="FM-20200826">{{cite journal |author=Kawaguchi, Yuko |display-authors=et al. |title=DNA Damage and Survival Time Course of Deinococcal Cell Pellets During 3 Years of Exposure to Outer Space |date=26 August 2020 |journal=[[Frontiers in Microbiology]] |volume=11 |page=2050 |doi=10.3389/fmicb.2020.02050 |pmid=32983036 |pmc=7479814 |s2cid=221300151 |doi-access=free }}</ref> In February 2023, findings of a "[[dark microbiome]]" of unfamiliar [[microorganism]]s in the [[Atacama Desert]] in [[Chile]], a [[Mars]]-like region of planet [[Earth]], were reported.<ref name="NC-20230221">{{cite journal |author=Azua-Bustos, Armando |display-authors=et al. |title=Dark microbiome and extremely low organics in Atacama fossil delta unveil Mars life detection limits |date=21 February 2023 |journal=[[Nature Communications]] |volume=14 |issue=808 |page=808 |doi=10.1038/s41467-023-36172-1 |pmid=36810853 |pmc=9944251 }}</ref> The total mass of the [[biosphere]] has been estimated to be as much as 4 trillion tons of [[carbon]].<ref name="AGCI-2015">{{cite web |url=http://www.agci.org/classroom/biosphere/index.php |title=The Biosphere: Diversity of Life |author=<!--Staff writer(s); no by-line.--> |work=Aspen Global Change Institute |location=Basalt, CO |access-date=19 July 2015 |archive-date=2 September 2010 |archive-url=https://web.archive.org/web/20100902111048/http://www.agci.org/classroom/biosphere/index.php}}</ref> According to one researcher, "You can find [[microbe]]s everywhere – [they are] extremely adaptable to conditions, and survive wherever they are."<ref name="LS-20130317" />


Of all [[species]] of life forms that ever lived on Earth, over five billion,<ref name="Book-Biology">{{cite book |url=https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 |title=The Biology of Rarity: Causes and consequences of rare – common differences |year=1996 |publisher=Springer |isbn=978-0-412-63380-5 |editor1=Kunin, W.E. |access-date=26 May 2015 |editor2=Gaston, Kevin}}</ref> more than 99% are estimated to be [[Extinction |extinct]].<ref name="StearnsStearns2000">{{cite book |last1=Stearns |first1=Beverly Peterson |last2=Stearns |first2=S. C. |last3=Stearns |first3=Stephen C. |title=Watching, from the Edge of Extinction |url=https://books.google.com/books?id=0BHeC-tXIB4C&q=99%20percent |year=2000 |publisher=[[Yale University Press]] |isbn=978-0-300-08469-6 |page=preface x |access-date=30 May 2017 }}</ref><ref name="NYT-20141108-MJN">{{cite news |last=Novacek |first=Michael J. |title=Prehistory's Brilliant Future |url=https://www.nytimes.com/2014/11/09/opinion/sunday/prehistorys-brilliant-future.html |date=8 November 2014 |work=The New York Times |access-date=25 December 2014 }}</ref> Some estimates on the number of Earth's current species range from 10 million to 14 million,<ref name="MillerSpoolman2012">{{cite book |author1=G. Miller |author2=Scott Spoolman |title=Environmental Science – Biodiversity Is a Crucial Part of the Earth's Natural Capital |url=https://books.google.com/books?id=NYEJAAAAQBAJ&pg=PA62 |date=2012 |publisher=[[Cengage Learning]] |isbn=978-1-133-70787-5 |page=62 |access-date=27 December 2014 }}</ref> of which about 1.2 million have been documented and over 86 percent remain undescribed.<ref name="PLoS-20110823">{{cite journal |last1=Mora |first1=C. |last2=Tittensor |first2=D.P. |last3=Adl |first3=S. |last4=Simpson |first4=A.G. |last5=Worm |first5=B. |title=How many species are there on Earth and in the ocean? |date=23 August 2011 |journal=[[PLOS Biology]] |doi=10.1371/journal.pbio.1001127 |pmid=21886479 |pmc=3160336 |volume=9 |issue=8 |pages=e1001127 |doi-access=free }}</ref> However, a May 2016 scientific report estimates 1 trillion species currently on Earth, with only one-thousandth of one percent described.<ref name="NSF-2016002">{{cite news |author=Staff |title=Researchers find that Earth may be home to 1 trillion species |url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446 |date=2 May 2016 |work=[[National Science Foundation]] |access-date=6 May 2016 }}</ref> Additionally, there are an estimated 10 nonillion (10 to the 31st power) individual [[virus]]es (including the related [[virion]]s) on Earth, the most numerous type of biological entity,<ref name="NRM-2005">{{cite journal | vauthors = Edwards RA, Rohwer F |title=Viral metagenomics |journal=[[Nature Reviews Microbiology]] |volume=3 |issue=6 |pages=504–10 |date=June 2005 |pmid=15886693 |doi=10.1038/nrmicro1163 |s2cid=8059643 }}</ref> which some biologists consider to be life forms.<ref name="SA-20080808">{{cite web |last=Villarreal |first=Luis P. |title=Are Viruses Alive? - Although viruses challenge our concept of what "living" means, they are vital members of the web of life |url=https://www.scientificamerican.com/article/are-viruses-alive-2004/ |date=8 August 2008 |work=[[Scientific American]] |access-date=19 May 2020 }}</ref>
Of all [[species]] of life forms that ever lived on Earth, over five billion,<ref name="Book-Biology">{{cite book |url=https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 |title=The Biology of Rarity: Causes and consequences of rare – common differences |year=1996 |publisher=Springer |isbn=978-0-412-63380-5 |editor1=Kunin, W.E. |access-date=26 May 2015 |editor2=Gaston, Kevin}}</ref> more than 99% are estimated to be [[Extinction |extinct]].<ref name="StearnsStearns2000">{{cite book |last1=Stearns |first1=Beverly Peterson |last2=Stearns |first2=S. C. |last3=Stearns |first3=Stephen C. |title=Watching, from the Edge of Extinction |url=https://books.google.com/books?id=0BHeC-tXIB4C&q=99%20percent |year=2000 |publisher=[[Yale University Press]] |isbn=978-0-300-08469-6 |page=preface x |access-date=30 May 2017 }}</ref><ref name="NYT-20141108-MJN">{{cite news |last=Novacek |first=Michael J. |title=Prehistory's Brilliant Future |url=https://www.nytimes.com/2014/11/09/opinion/sunday/prehistorys-brilliant-future.html |date=8 November 2014 |work=The New York Times |access-date=25 December 2014 }}</ref> Some estimates on the number of Earth's current species range from 10 million to 14 million,<ref name="MillerSpoolman2012">{{cite book |author1=G. Miller |author2=Scott Spoolman |title=Environmental Science – Biodiversity Is a Crucial Part of the Earth's Natural Capital |url=https://books.google.com/books?id=NYEJAAAAQBAJ&pg=PA62 |date=2012 |publisher=[[Cengage Learning]] |isbn=978-1-133-70787-5 |page=62 |access-date=27 December 2014 }}</ref> of which about 1.2 million have been documented and over 86 percent remain undescribed.<ref name="PLoS-20110823">{{cite journal |last1=Mora |first1=C. |last2=Tittensor |first2=D.P. |last3=Adl |first3=S. |last4=Simpson |first4=A.G. |last5=Worm |first5=B. |title=How many species are there on Earth and in the ocean? |date=23 August 2011 |journal=[[PLOS Biology]] |doi=10.1371/journal.pbio.1001127 |pmid=21886479 |pmc=3160336 |volume=9 |issue=8 |pages=e1001127 |doi-access=free }}</ref> However, a May 2016 scientific report estimates 1 trillion species currently on Earth, with only one-thousandth of one percent described.<ref name="NSF-2016002">{{cite news |author=Staff |title=Researchers find that Earth may be home to 1 trillion species |url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446 |date=2 May 2016 |work=[[National Science Foundation]] |access-date=6 May 2016 }}</ref> Additionally, there are an estimated 10 nonillion (10 to the 31st power) individual [[virus]]es (including the related [[virion]]s) on Earth, the most numerous type of biological entity,<ref name="NRM-2005">{{cite journal | vauthors = Edwards RA, Rohwer F |title=Viral metagenomics |journal=[[Nature Reviews Microbiology]] |volume=3 |issue=6 |pages=504–10 |date=June 2005 |pmid=15886693 |doi=10.1038/nrmicro1163 |s2cid=8059643 }}</ref> which some biologists consider to be life forms.<ref name="SA-20080808">{{cite web |last=Villarreal |first=Luis P. |title=Are Viruses Alive? - Although viruses challenge our concept of what "living" means, they are vital members of the web of life |url=https://www.scientificamerican.com/article/are-viruses-alive-2004/ |date=8 August 2008 |work=[[Scientific American]] |access-date=19 May 2020 }}</ref>

Revision as of 21:09, 14 November 2023

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 evidence of life on Earth is from microfossils of microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks, although the validity of these microfossils is debated.

Biospheres

Further information: Abiogenesis

Earth remains the only place in the universe known to harbor life.[3][4] The origin of life on Earth was at least 3.77 billion years ago, possibly as early as 4.28–4.5 billion years ago.[2][5][6] The Earth's biosphere extends down to at least 19 km (12 mi) below the surface,[7][better source needed] and up to at least 76 km (47 mi)[8] into the atmosphere,[9][10][11] and includes soil, hydrothermal vents, and rock.[12][13] Further, the biosphere has been found to extend at least 914.4 m (3,000 ft; 0.5682 mi) below the ice of Antarctica,[14][15] and includes the deepest parts of the ocean,[16][17] down to rocks kilometers below the sea floor.[16][18][19] 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.[20] Under certain test conditions, life forms have been observed to survive in the vacuum of outer space.[21][22] 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.[23] 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.[24] The total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon.[25] According to one researcher, "You can find microbes everywhere – [they are] extremely adaptable to conditions, and survive wherever they are."[16]

Of all species of life forms that ever lived on Earth, over five billion,[26] more than 99% are estimated to be extinct.[27][28] Some estimates on the number of Earth's current species range from 10 million to 14 million,[29] of which about 1.2 million have been documented and over 86 percent remain undescribed.[30] However, a May 2016 scientific report estimates 1 trillion species currently on Earth, with only one-thousandth of one percent described.[31] Additionally, there are an estimated 10 nonillion (10 to the 31st power) individual viruses (including the related virions) on Earth, the most numerous type of biological entity,[32] which some biologists consider to be life forms.[33]

Fossil evidence

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

The age of Earth is about 4.54 billion years;[34][35][36] the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago.[37] Some computer models suggest life began as early as 4.5 billion years ago.[5][6]

3.465-billion-year-old Australian Apex chert rocks may once have contained microorganisms, the earliest fossil evidence of life on Earth,[38][39] although the validity of these findings has been contested.[40] Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia.[41][42] Evidence of biogenic graphite,[43][44] and possibly stromatolites,[45][46][47] 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.[48] "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[49] or meteorites.[50]

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.[5][6] According to biologist Stephen Blair Hedges, "If life arose relatively quickly on Earth ... then it could be common in the universe".[51][52][53] The possibility that terrestrial life forms may have been seeded from outer space has been considered.[54][55] 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.[50]

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.[56][57][58] In July 2018, scientists reported that the earliest life on land may have been bacteria 3.22 billion years ago.[59] 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.[60][61]

Genomic evidence

Main article: Last universal common ancestor

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.[62] A molecular clock model suggests that the LUCA may have lived 4.477—4.519 billion years ago, within the Hadean eon.[5][6][a]

Earliest known life forms

See also

Footnotes

  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.

References

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