Editing Biodiversity (section)

=== Species diversity in geologic time frames ===
{{Further|History of life|Earliest known life forms}}

It is estimated that 5 to 50 billion species have existed on the planet.<ref>{{Cite journal |last=Barry |first=John C. |date=1992 |title=Extinction: Bad genes or bad luck? By David M. Raup. New York: W. W. Norton. 1991. xvii + 210 pp. ISBN 0-393-03008-3. $19.95 (cloth) |journal=American Journal of Physical Anthropology |volume=88 |issue=4 |pages=563–564 |doi=10.1002/ajpa.1330880410 }}</ref> Assuming that there may be a maximum of about 50 million species currently alive,<ref>{{Cite journal |last=May |first=Robert M. |date=1988-09-16 |title=How Many Species Are There on Earth? |journal=Science |volume=241 |issue=4872 |pages=1441–1449 |doi=10.1126/science.241.4872.1441 |pmid=17790039 |bibcode=1988Sci...241.1441M }}</ref> it stands to reason that greater than 99% of the planet's species went extinct prior to the evolution of humans.<ref>{{cite book |doi=10.1007/978-94-011-5874-9_7 |chapter=How do rare species avoid extinction? A paleontological view |title=The Biology of Rarity |date=1997 |last1=McKinney |first1=Michael L. |pages=110–129 |isbn=978-94-010-6483-5 }}</ref> Estimates on the number of Earth's current [[species]] range from 10&nbsp;million to 14&nbsp;million, of which about 1.2&nbsp;million have been documented and over 86% have not yet been described.<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 |accessdate=27 December 2014 }}</ref> However, a May 2016 scientific report estimates that 1 trillion species are 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]] |accessdate=6 May 2016 }}</ref> The total amount of related [[DNA]] [[base pair]]s on Earth is estimated at 5.0 x 10<sup>37</sup> and weighs 50&nbsp;billion [[tonne]]s. In comparison, the total [[Biomass (ecology)|mass]] of the [[biosphere]] has been estimated to be as much as four trillion tons of [[carbon]].<ref name="AGCI-2014">{{cite web |author=Staff |title=The Biosphere |url=http://www.agci.org/classroom/biosphere/index.php |date=2014 |work=[[The Given Institute|Aspen Global Change Institute]] |access-date=10 November 2014 |archive-url=https://web.archive.org/web/20141110164609/http://www.agci.org/classroom/biosphere/index.php |archive-date=10 November 2014 |url-status=live }}</ref> In July 2016, scientists reported identifying a set of 355 [[gene]]s from the [[last universal common ancestor]] (LUCA) of all [[organism]]s living on Earth.<ref name="NYT-20160725">{{cite news |last=Wade |first=Nicholas |authorlink=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=[[New York Times]] |accessdate=25 July 2016 }}</ref>

The [[age of Earth]] is about 4.54&nbsp;billion years.<ref name="USGS1997">{{cite web |url=http://pubs.usgs.gov/gip/geotime/age.html |title=Age of the Earth |date=9 July 2007 |publisher=[[United States Geological Survey]] |accessdate=2006-01-10}}</ref><ref>{{cite journal |last=Dalrymple |first=G. Brent | authorlink=Brent Dalrymple  | title=The age of the Earth in the twentieth century: a problem (mostly) solved | journal=Special Publications, Geological Society of London | date=2001 | volume=190 | issue=1 | pages=205–221 | doi=10.1144/GSL.SP.2001.190.01.14 |bibcode = 2001GSLSP.190..205D }}</ref><ref>{{cite journal |last1=Manhes |first1=Gérard |last2=Allègre |first2=Claude J. |last3=Dupré |first3=Bernard |last4=Hamelin |first4=Bruno |title=Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics |journal=Earth and Planetary Science Letters |date=May 1980 |volume=47 |issue=3 |pages=370–382 |doi=10.1016/0012-821X(80)90024-2 |bibcode=1980E&PSL..47..370M }}</ref> The earliest undisputed evidence of [[life]] dates at least from 3.7&nbsp;billion years ago, during the [[Eoarchean]] era after a geological [[Crust (geology)|crust]] started to solidify following the earlier molten [[Hadean]] eon.<ref name="Origin1">{{cite journal |last1=Schopf |first1=J. William |authorlink1=J. William Schopf |last2=Kudryavtsev |first2=Anatoliy B. |last3=Czaja |first3=Andrew D. |last4=Tripathi |first4=Abhishek B. |date=5 October 2007 |title=Evidence of Archean life: Stromatolites and microfossils |journal=[[Precambrian Research]] |location=Amsterdam, the Netherlands |publisher=Elsevier |volume=158 |pages=141–155 |issue=3–4 |doi=10.1016/j.precamres.2007.04.009 |bibcode=2007PreR..158..141S }}</ref><ref name="Origin2">{{cite journal |last=Schopf |first=J. William |date=29 June 2006 |title=Fossil evidence of Archaean life |journal=[[Philosophical Transactions of the Royal Society B]] |location=London |publisher=[[Royal Society]] |volume=361 |issue=1470 |pages=869–885 |doi=10.1098/rstb.2006.1834 |pmid=16754604 |pmc=1578735}}</ref><ref name="RavenJohnson2002">{{cite book |last1=Raven |first1=Peter H. |authorlink1=Peter H. Raven |last2=Johnson |first2=George B. |authorlink2=George B. Johnson |year=2002 |title=Biology |edition=6th |location=Boston, MA |publisher=[[McGraw-Hill Education|McGraw-Hill]] |isbn=0-07-112261-3 |lccn=2001030052 |oclc=45806501 |page=68}}</ref> There are [[microbial mat]] [[fossils]] found in 3.48&nbsp;billion-year-old [[sandstone]] discovered in [[Western Australia]]. Other early physical evidence of a [[biogenic substance]] is [[graphite]] in 3.7&nbsp;billion-year-old [[Metasediment|meta-sedimentary rocks]] discovered in [[Western Greenland]]..<ref name="NG-201312083">{{cite journal |last1=Ohtomo |first1=Yoko |last2=Kakegawa |first2=Takeshi |last3=Ishida |first3=Akizumi |last4=Nagase |first4=Toshiro |last5=Rosing |first5=Minik T. |title=Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks |journal=Nature Geoscience |date=January 2014 |volume=7 |issue=1 |pages=25–28 |doi=10.1038/ngeo2025 |bibcode=2014NatGe...7...25O }}</ref><ref name=":02">{{Cite journal |last1=Hassenkam |first1=T. |last2=Rosing |first2=M. T. |date=2017-11-02 |title=3.7 billion year old biogenic remains |journal=Communicative & Integrative Biology |language=en |volume=10 |issue=5–6 |pages=e1380759 |doi=10.1080/19420889.2017.1380759 |pmc=5731516 |pmid=29260796}}</ref> More recently, in 2015, "remains of [[Biotic material|biotic life]]" were found in 4.1&nbsp;billion-year-old rocks in Western [[Australia]]. According to one of the researchers, "If life arose relatively quickly on Earth...then it could be common in the [[universe]]."<ref name="apnews.excite.com 2015">{{cite news |last1=Borenstein |first1=Seth |title=Hints of life on what was thought to be desolate early Earth |url=https://apnews.com/hints-of-life-on-what-was-thought-to-be-desolate-early-earth-e6be2537b4cd46ffb9c0585bae2b2e51 |work=AP News |date=19 October 2015 }}</ref>