Editing Earth (section)

=== Origin of life and evolution ===
{{Main|Abiogenesis|Earliest known life forms|History of life}}
[[Chemical reaction]]s led to the first self-replicating molecules about four billion years ago. A half billion years later, the [[last universal common ancestor|last common ancestor of all current life]] arose.<ref name="sa282_6_90" /> The evolution of [[photosynthesis]] allowed the Sun's energy to be harvested directly by life forms. The resultant [[molecular oxygen]] (O2) accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective [[ozone layer]] (O3) in the upper atmosphere.<ref name="NYT-20131003">{{cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |title=Earth's Oxygen: A Mystery Easy to Take for Granted |url=https://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |archive-url=https://web.archive.org/web/20131003121909/http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |archive-date=3 October 2013 |url-access=limited |date=3 October 2013 |work=[[The New York Times]] |access-date=3 October 2013}}</ref> The incorporation of smaller cells within larger ones resulted in the [[endosymbiotic theory|development of complex cells]] called [[eukaryote]]s.<ref name="jas22_3_225" /> True multicellular organisms formed as cells within [[Colony (biology)|colonies]] became increasingly specialized. Aided by the absorption of harmful [[ultraviolet radiation]] by the ozone layer, life colonized Earth's surface.<ref name="burton20021129" /> Among the earliest [[fossil]] evidence for life is [[microbial mat]] fossils found in 3.48&nbsp;billion-year-old [[sandstone]] in [[Western Australia]],<ref>{{cite journal |last1=Noffke |first1=Nora |author-link=Nora Noffke |last2=Christian |first2=Daniel |last3=Wacey |first3=David |last4=Hazen |first4=Robert M. |author4-link=Robert Hazen |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]] |doi=10.1089/ast.2013.1030 |bibcode=2013AsBio..13.1103N |pmid=24205812 |pmc=3870916 |volume=13 |issue=12 |pages=1103–1124}}</ref> [[Biogenic substance|biogenic]] [[graphite]] found in 3.7&nbsp;billion-year-old [[metasediment]]ary rocks in [[Western Greenland]],<ref>{{cite journal |last1=Ohtomo |first1=Yoko |last2=Kakegawa |first2=Takeshi |last3=Ishida |first3=Akizumi |last4=Nagase |first4=Toshiro |last5=Rosing |first5=Minik T. |s2cid=54767854 |display-authors=3 |date=January 2014 |title=Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks |journal=[[Nature Geoscience]] |volume=7 |issue=1 |pages=25–28 |bibcode=2014NatGe...7...25O |doi=10.1038/ngeo2025 |issn=1752-0894}}</ref> and remains of [[biotic material]] found in 4.1&nbsp;billion-year-old rocks in Western Australia.<ref>{{cite news |last=Borenstein |first=Seth |title=Hints of life on what was thought to be desolate early Earth |url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |date=19 October 2015 |work=[[Excite (web portal)|Excite]] |location=Yonkers, NY |publisher=[[Mindspark Interactive Network]] |agency=[[Associated Press]] |access-date=20 October 2015 |archive-url=https://web.archive.org/web/20160818063111/https://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |archive-date=18 August 2016}}</ref><ref>{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |author-link3=T. Mark Harrison |last4=Mao |first4=Wendy L. |author4-link=Wendy Mao |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1&nbsp;billion-year-old zircon |journal=Proc. Natl. Acad. Sci. U.S.A. |doi=10.1073/pnas.1517557112 |issn=1091-6490 |pmid=26483481 |pmc=4664351 |volume=112 |issue=47 |pages=14518–4521 |bibcode=2015PNAS..11214518B |doi-access=free}} Early edition, published online before print.</ref> The [[Earliest known life forms|earliest direct evidence of life]] on Earth is contained in 3.45&nbsp;billion-year-old [[Australia (continent)|Australian]] rocks showing fossils of [[microorganism]]s.<ref>{{cite web |last=Tyrell |first=Kelly April |title=Oldest fossils ever found show life on Earth began before 3.5 billion years ago |url=https://news.wisc.edu/oldest-fossils-ever-found-show-life-on-earth-began-before-3-5-billion-years-ago/ |date=18 December 2017 |publisher=[[University of Wisconsin–Madison]] |access-date=18 December 2017 |archive-date=31 March 2021 |archive-url=https://web.archive.org/web/20210331100351/https://news.wisc.edu/oldest-fossils-found-show-life-began-before-3-5-billion-years-ago/ |url-status=live }}</ref><ref>{{cite journal |last1=Schopf |first1=J. William |last2=Kitajima |first2=Kouki |last3=Spicuzza |first3=Michael J. |last4=Kudryavtsev |first4=Anatolly B. |last5=Valley |first5=John W. |title=SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions |year=2017 |journal=[[Proceedings of the National Academy of Sciences of the United States of America|PNAS]] |volume=115 |issue=1 |pages=53–58 |doi=10.1073/pnas.1718063115 |pmid=29255053 |pmc=5776830 |bibcode=2018PNAS..115...53S |doi-access=free}}</ref>[[File:Archean.png|right|thumb|500x500px|An artist's impression of the [[Archean]], the [[Geologic time scale#Divisions of geologic time|eon]] after Earth's formation, featuring round [[stromatolite]]s, which are early oxygen-producing forms of life from billions of years ago. After the [[Late Heavy Bombardment]], [[Earth's crust]] had cooled, its water-rich barren [[planetary surface|surface]] is marked by [[continent]]s and [[volcano]]es, with the Moon still orbiting Earth half as far as it is today, appearing 2.8 times larger and producing strong [[tide]]s.<ref name="Lunar and Planetary Institute">{{cite web |title=Earth-Moon Dynamics |url=https://www.lpi.usra.edu/exploration/training/illustrations/earthMoon/ |access-date=2 September 2022 |website=Lunar and Planetary Institute |archive-date=7 September 2015 |archive-url=https://web.archive.org/web/20150907215806/https://www.lpi.usra.edu/exploration/training/illustrations/earthMoon/ |url-status=live }}</ref>]]During the [[Neoproterozoic]], 1000nto 539 Ma, much of Earth might have been covered in ice. This hypothesis has been termed "[[Snowball Earth]]", and it is of particular interest because it preceded the [[Cambrian explosion]], when multicellular life forms significantly increased in complexity.<ref>{{cite book|page=42|title=Climate Change and the Course of Global History|last1=Brooke|first1=John L.|year= 2014|publisher=Cambridge University Press|isbn=978-0-521-87164-8}}</ref><ref>{{cite book|page=56|title=Epigenetic Mechanisms of the Cambrian Explosion|last1=Cabej|first1=Nelson R.|year=2019|publisher=Elsevier Science|isbn=978-0-12-814312-4}}</ref> Following the Cambrian explosion, 53 Ma, there have been at least five major [[Extinction event|mass extinctions]] and many minor ones.<ref name="Stanley_2016" /> Apart from the proposed current [[Holocene extinction]] event, the [[Cretaceous–Paleogene extinction event|most recent]] was 66 Ma, when [[Chicxulub impactor|an asteroid impact]] triggered the extinction of non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, [[mammal]]s, lizards and birds. Mammalian life has diversified over the past 66 Mys, and several million years ago, an African [[ape]] species gained the ability to stand upright.<ref name="gould1994" /><ref>{{Cite journal |last1=Daver |first1=G. |last2=Guy |first2=F. |last3=Mackaye |first3=H. T. |last4=Likius |first4=A. |last5=Boisserie |first5=J.-R. |last6=Moussa |first6=A. |last7=Pallas |first7=L. |last8=Vignaud |first8=P. |last9=Clarisse |first9=N. D. |date=2022 |title=Postcranial evidence of late Miocene hominin bipedalism in Chad |url=https://www.nature.com/articles/s41586-022-04901-z |journal=Nature |language=en |volume=609 |issue=7925 |pages=94–100 |doi=10.1038/s41586-022-04901-z |pmid=36002567 |bibcode=2022Natur.609...94D |issn=1476-4687 |access-date=29 March 2024 |archive-date=27 August 2022 |archive-url=https://web.archive.org/web/20220827082104/https://www.nature.com/articles/s41586-022-04901-z |url-status=live }}</ref> This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which led to the [[Human evolution|evolution of humans]]. The [[History of agriculture|development of agriculture]], and then [[List of ancient civilizations|civilization]], led to humans having an [[Human impact on the environment|influence on Earth]] and the nature and quantity of other life forms that continues to this day.<ref name="bgsa119_1_140" />