Life Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Origin of life === {{Main|Abiogenesis}} The [[age of Earth]] is about 4.54 [[Bya|billion years]].<ref>{{cite journal |last=Dalrymple |first=G. Brent |title=The age of the Earth in the twentieth century: a problem (mostly) solved |journal=Special Publications, Geological Society of London |year=2001 |volume=190 |issue=1 |pages=205β221 |doi=10.1144/GSL.SP.2001.190.01.14 |bibcode=2001GSLSP.190..205D|s2cid=130092094 }}</ref> Life on Earth has existed for at least 3.5 billion years,<ref name="PNAS-20151014-pdf">{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |last4=Mao |first4=Wendy L. |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon |url=http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf |journal=PNAS |doi=10.1073/pnas.1517557112 |pmid=26483481 |pmc=4664351 |volume=112 |issue=47 |pages=14518β14521 |bibcode=2015PNAS..11214518B |url-status=live |archive-url=https://web.archive.org/web/20151106021508/http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf |archive-date=6 November 2015 |doi-access=free }}</ref><ref>{{Cite journal |title=Fossil evidence of Archaean life |journal=Philos. Trans. R. Soc. Lond. B Biol. Sci. |volume=361 |issue=1470 |pmc=1578735|doi=10.1098/rstb.2006.1834 |pmid=16754604 |date=June 2006 |pages=869β885 | last1 = Schopf | first1 = J.W.}}</ref><ref name="RavenJohnson2002">{{cite book |first1=Peter |last1=Hamilton Raven |first2=George |last2=Brooks Johnson |title=Biology |url=https://archive.org/details/biologyrave00rave |url-access=registration |date=2002 |publisher=McGraw-Hill Education |isbn=978-0-07-112261-0 |page=[https://archive.org/details/biologyrave00rave/page/68 68] |access-date=7 July 2013 }}</ref><ref>{{cite book |first1=Clare |last1=Milsom |first2=Sue |last2=Rigby |author2-link=Sue Rigby |title=Fossils at a Glance |edition=2nd |publisher=John Wiley & Sons |date=2009 |isbn=978-1-4051-9336-8 |page=134 |url=https://books.google.com/books?id=OdrCdxr7QdgC&pg=PA134 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194758/https://books.google.com/books?id=OdrCdxr7QdgC&pg=PA134 |url-status=live }}</ref> with the oldest physical [[Trace fossil|traces]] of life dating back 3.7 billion years.<ref name="NG-20131208">{{cite journal |first1=Yoko |last1=Ohtomo |first2=Takeshi |last2=Kakegawa |first3=Akizumi |last3=Ishida |first4=Toshiro |last4=Nagase |first5=Minik T. |last5=Rosing |title=Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks |journal=[[Nature Geoscience]] |doi=10.1038/ngeo2025 |date=8 December 2013 |volume=7 |issue=1 |pages=25β28 |bibcode=2014NatGe...7...25O}}</ref><ref name="AST-20131108">{{cite journal |last1=Noffke |first1=Nora |author-link=Nora Noffke |last2=Christian |first2=Daniel |last3=Wacey |first3=David |last4=Hazen |first4=Robert M. |title=Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia |date=8 November 2013 |journal=[[Astrobiology (journal)|Astrobiology]] |volume=13 |issue=12 |pages=1103β1124 |doi=10.1089/ast.2013.1030 |bibcode=2013AsBio..13.1103N |pmid=24205812 |pmc=3870916}}</ref> Estimates from molecular clocks, as summarized in the [[TimeTree]] public database, place the origin of life around 4.0 billion years ago.<ref>{{cite book |last=Hedges |first=S. B. Hedges |chapter=Life |pages=89β98 |title=The Timetree of Life |editor1=S. B. Hedges |editor2=S. Kumar |publisher=Oxford University Press |year=2009 |isbn=978-0-1995-3503-3}}</ref> Hypotheses on the origin of life attempt to explain the formation of a [[universal common ancestor]] from simple [[organic molecule]]s via pre-cellular life to [[protocell]]s and metabolism.<ref>{{cite web |url=http://phoenix.lpl.arizona.edu/mars145.php |title=Habitability and Biology: What are the Properties of Life? |access-date=6 June 2013 |website=Phoenix Mars Mission |publisher=The University of Arizona |url-status=live |archive-url=https://web.archive.org/web/20140417155949/http://phoenix.lpl.arizona.edu/mars145.php |archive-date=17 April 2014 }}</ref> In 2016, a set of 355 [[gene]]s from the [[last universal common ancestor]] was tentatively identified.<ref name="NYT-20160725">{{cite news |last=Wade |first=Nicholas |author-link=Nicholas Wade |title=Meet Luca, the Ancestor of All Living Things |url=https://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html |date=25 July 2016 |work=[[The New York Times]] |access-date=25 July 2016 |url-status=live |archive-url=https://web.archive.org/web/20160728053822/http://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html |archive-date=28 July 2016 }}</ref> The biosphere is postulated to have developed, from the origin of life onwards, at least some 3.5 billion years ago.<ref name="Campbell 2006">{{cite book |last=Campbell |first=Neil A. |author2=Brad Williamson |author3=Robin J. Heyden |title=Biology: Exploring Life |publisher=Pearson Prentice Hall |year=2006 |location=Boston, Massachusetts |url=http://www.phschool.com/el_marketing.html |isbn=978-0-13-250882-7 |url-status=dead |archive-url=https://web.archive.org/web/20141102041816/http://www.phschool.com/el_marketing.html |archive-date=2 November 2014 |access-date=15 June 2016 }}</ref> The earliest evidence for life on Earth includes [[Biogenic substance|biogenic]] [[graphite]] found in 3.7 billion-year-old [[Metasediment|metasedimentary rocks]] from [[Western Greenland]]<ref name="NG-20131208"/> and [[microbial mat]] [[fossils]] found in 3.48 billion-year-old [[sandstone]] from [[Western Australia]].<ref name="AST-20131108"/> More recently, in 2015, "remains of [[Biotic material|biotic life]]" were found in 4.1 billion-year-old rocks in Western Australia.<ref name="PNAS-20151014-pdf"/> In 2017, putative fossilised [[microorganism]]s (or [[Micropaleontology#Microfossils|microfossils]]) were announced to have been discovered in [[hydrothermal vent|hydrothermal vent precipitates]] in the [[Nuvvuagittuq Greenstone Belt|Nuvvuagittuq Belt]] of Quebec, Canada that were as old as 4.28 billion years, the oldest record of life on Earth, suggesting "an almost instantaneous emergence of life" after [[Origin of water on Earth#History of water on Earth|ocean formation 4.4 billion years ago]], and not long after the [[Age of the Earth|formation of the Earth]] 4.54 billion years ago.<ref name="NAT-20170301">{{cite journal |last1=Dodd |first1=Matthew S. |last2=Papineau |first2=Dominic |last3=Grenne |first3=Tor |last4=Slack |first4=John F. |last5=Rittner |first5=Martin |last6=Pirajno |first6=Franco |last7=O'Neil |first7=Jonathan |last8=Little |first8=Crispin T.S. |title=Evidence for early life in Earth's oldest hydrothermal vent precipitates |url=http://eprints.whiterose.ac.uk/112179/ |journal=[[Nature (journal)|Nature]] |date=1 March 2017 |volume=543 |issue=7643 |pages=60β64 |doi=10.1038/nature21377 |pmid=28252057 |access-date=2 March 2017 |bibcode=2017Natur.543...60D |url-status=live |archive-url=https://web.archive.org/web/20170908201821/http://eprints.whiterose.ac.uk/112179/ |archive-date=8 September 2017 |doi-access=free }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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