Editing Cell (biology) (section)

=== Origin of life ===

{{further|Abiogenesis|Evolution of cells}}

[[File:Stromatolites.jpg|thumb|[[Stromatolites]] are left behind by [[cyanobacteria]], also called blue-green algae. They are among the oldest fossils of life on Earth. This one-billion-year-old fossil is from [[Glacier National Park (U.S.)|Glacier National Park]] in the United States.]]

Small molecules needed for life may have been carried to Earth on meteorites, created at [[Hydrothermal vent|deep-sea vents]], or [[Miller–Urey experiment|synthesized by lightning in a reducing atmosphere]]. There is little experimental data defining what the first self-replicating forms were. [[RNA]] may have been [[RNA world hypothesis|the earliest self-replicating molecule]], as it can both store genetic information and catalyze chemical reactions.<ref name=OrgelLE>{{cite journal |last= Orgel |first=L. E. |title=The origin of life--a review of facts and speculations |journal=Trends in Biochemical Sciences |volume=23 |issue=12 |pages=491–495 |date=December 1998 |pmid=9868373 |doi=10.1016/S0968-0004(98)01300-0 }}</ref>

Cells emerged around 4 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. |display-authors=3 |title=Evidence for early life in Earth's oldest hydrothermal vent precipitates |journal=[[Nature (journal)|Nature]] |date=1 March 2017 |volume=543 |issue=7643 |pages=60–64 |doi=10.1038/nature21377 |doi-access=free |pmid=28252057 |bibcode=2017Natur.543...60D |url=http://eprints.whiterose.ac.uk/112179/ |access-date=2 March 2017 |url-status=live |archive-url=https://web.archive.org/web/20170908201821/http://eprints.whiterose.ac.uk/112179/ |archive-date=8 September 2017}}</ref><ref>{{Cite journal |last1=Betts |first1=Holly C. |last2=Puttick |first2=Mark N. |last3=Clark |first3=James W. |last4=Williams |first4=Tom A. |last5=Donoghue |first5=Philip C. J. |last6=Pisani |first6=Davide |date=20 August 2018 |title=Integrated genomic and fossil evidence illuminates life's early evolution and eukaryote origin |journal=Nature Ecology & Evolution |volume=2 |issue=10 |pages=1556–1562 |doi=10.1038/s41559-018-0644-x |pmid=30127539|pmc=6152910 |bibcode=2018NatEE...2.1556B }}</ref> The first cells were most likely [[heterotroph]]s. The early cell membranes were probably simpler and more permeable than modern ones, with only a single fatty acid chain per lipid. Lipids spontaneously form bilayered [[Vesicle (biology and chemistry)|vesicles]] in water, and could have preceded RNA.<ref name="Griffiths 2007">{{cite journal |last=Griffiths |first=G. |title=Cell evolution and the problem of membrane topology |journal=Nature Reviews. Molecular Cell Biology |volume=8 |issue=12 |pages=1018–1024 |date=December 2007 |pmid=17971839 |doi=10.1038/nrm2287 |s2cid=31072778 |doi-access=free }}</ref><ref name="ScienceDaily 2021">{{cite web |title=First cells may have emerged because building blocks of proteins stabilized membranes |url=https://www.sciencedaily.com/releases/2019/08/190812155502.htm |access-date=2021-09-18 |website=ScienceDaily |archive-date=2021-09-18 |archive-url=https://web.archive.org/web/20210918102211/https://www.sciencedaily.com/releases/2019/08/190812155502.htm |url-status=live }}</ref>