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{{Short description|Scottish chemist (1931-2016)}}
{{Use dmy dates|date=April 2017}}
{{Use British English|date=April 2017}}
'''Alexander Graham Cairns-Smith''' [[FRSE]] (24 November 1931 – 26 August 2016) was an [[organic chemist]] and [[molecular biologist]] at the [[University of Glasgow]].<ref>{{cite book |url=https://books.google.com/books?id=Vws5AAAAIAAJ&q=Alexander+Graham+Cairns-Smith+1931 |title=Who's who of British Scientists |year=1971 |isbn=9780582114647}}</ref> He studied at the University of Edinburgh, where he gained a Ph.D. in Chemistry (1957).<ref>{{cite journal |last=Cairns Smith |first=A. G. |date=1957 |title=Studies in the acridine series |url=https://era.ed.ac.uk/handle/1842/29033 }}</ref> He was most famous for his controversial 1985 book ''Seven Clues to the Origin of Life''.
The book popularized a hypothesis he began to develop in the mid-1960s—that self-replication of [[clay]] crystals in solution might provide a simple intermediate step between biologically inert matter and [[organic life]]. He inspired other ideas about [[Abiogenesis|chemical evolution]], including the [[Miller–Urey experiment]] and the [[RNA World]], all of which are hypotheses that have greatly helped in explaining the [[origin of life]].▼
▲The book popularized a hypothesis he began to develop in the mid-1960s—that self-replication of [[clay]] crystals in solution might provide a simple intermediate step between biologically inert matter and [[organic life]]. He inspired other ideas about [[Abiogenesis|chemical evolution]], including the [[Miller–Urey experiment]] and the [[RNA World]], all of which are hypotheses that have
Cairns-Smith also published on the [[evolution]] of [[consciousness]], in ''Evolving the Mind'' (1996), favoring a role for [[quantum mechanics]] in human [[thought]].<ref>{{cite journal | last=Dennett | first=Daniel | url=http://cogprints.org/289/ | title=Quantum Incoherence: Review of Cairns-Smith, ''Evolving the Mind'' | journal=[[Nature (journal)|Nature]] | volume=381 | year=1996 | pages=486 |bibcode = 1996Natur.381..486T |doi = 10.1038/381486a0 }}</ref>▼
▲Cairns-Smith also published on the [[evolution]] of [[consciousness]], in ''Evolving the Mind'' (1996), favoring a role for [[quantum mechanics]] in human [[thought]].<ref>{{cite journal | last=Dennett | first=Daniel | url=http://cogprints.org/289/ | title=Quantum Incoherence: Review of Cairns-Smith, ''Evolving the Mind'' | journal=[[Nature (journal)|Nature]] | volume=381 | year=1996 | issue=6582 | pages=486 |bibcode = 1996Natur.381..486T |doi = 10.1038/381486a0 | s2cid=39799295 | doi-access=free }}</ref> He died on 26 August 2016.<ref>{{cite web |title=Cairns-Smith |url=http://announcements.telegraph.co.uk/deaths/206038/cairns-smith |website=Telegraph.co.uk |access-date=1 January 2022}}</ref>
The '''clay hypothesis''' suggests how biologically inert matter helped the evolution of early life forms: [[clay mineral]]s form naturally from [[Silicate minerals|silicates]] in solution. Clay crystals, as other [[crystals]], preserve their external formal arrangement as they grow, snap, and grow further. Clay crystal masses of a particular external form may happen to affect their [[natural environment|environment]] in ways that affect their chances of further replication. For example, a "stickier" clay crystal is more likely to [[silt]] a stream bed, creating an environment conducive to further [[sedimentation]]. It is conceivable that such effects could extend to the creation of flat areas likely to be exposed to air, dry, and turn to wind-borne dust, which could fall randomly in other streams. Thus—by simple, inorganic, physical processes—a selection environment might exist for the reproduction of clay crystals of the "stickier" shape.▼
==Clay hypothesis<!-- Links to this section on: History of Earth-->==
There follows a process of natural selection for clay crystals that trap certain forms of [[molecules]] to their surfaces that may enhance their replication potential. Complex proto-organic molecules can be [[Catalysis|catalysed]] by the surface properties of [[Silicate minerals|silicates]]. When complex molecules perform a "genetic takeover" from their clay "vehicle", become an independent locus of replication – an evolutionary moment that might be understood as the first [[exaptation]].▼
▲The '''clay hypothesis''' suggests how biologically inert matter helped the evolution of early life forms: [[clay mineral]]s form naturally from [[Silicate minerals|silicates]] in solution. Clay crystals, as other [[crystals]], preserve their external formal arrangement as they grow, snap,{{clarify|date=July 2019}} and grow further. Clay crystal masses of a particular external form may happen to affect their [[natural environment|environment]] in ways that affect their chances of further replication. For example, a "stickier" clay crystal is more likely to [[silt]] a stream bed, creating an environment conducive to further [[sedimentation]]. It is conceivable that such effects could extend to the creation of flat areas likely to be exposed to air, dry, and turn to wind-borne dust, which could fall randomly in other streams. Thus—by simple, inorganic, physical processes—a selection environment might exist for the reproduction of clay crystals of the "stickier" shape.<ref>{{cite book |last=Dawkins |first=Richard |author-link=Richard Dawkins |title=The Blind Watchmaker: why the evidence of evolution reveals a universe without design |year=2015 |publisher=W. W. Norton & Company |isbn=978-0393351491 |page=156}}</ref>
▲There follows a process of natural selection for clay crystals that trap certain forms of [[molecules]] to their surfaces that may enhance their replication potential. Complex proto-organic molecules can be [[Catalysis|catalysed]] by the surface properties of [[Silicate minerals|silicates]]. When complex molecules perform a "genetic takeover" from their clay "vehicle", they become an independent locus of replication – an evolutionary moment that might be understood as the first [[exaptation]].
==Selected publications==
* {{citation | last=Cairns-Smith | first=Alexander Graham | chapter=An approach to a blueprint for a primitive organism |chapter-url=https://books.google.com/books?id=fMJwt2rr80MC&q=%22Cairns-Smith%22&pg=PA1 | editor-last=Waddington | editor-first=C. H. | title=The Origin of Life: Towards a Theoretical Biology | pages=57–66 | isbn=978-0-202-36302-8 | year=2009 | publisher=Aldine Transaction | volume=1 |ref=none }} Reissue of {{citation | editor-last=Waddington | editor-first=C. H. | title=Towards a Theoretical Biology: Prolegomena | volume=1 | year=1968 | publisher=Edinburgh University Press | isbn=978-0852240182 |ref=none }}
* {{citation | last=Cairns-Smith | first=Alexander Graham | title=Genetic Takeover and the Mineral Origins of Life | url=https://books.google.com/books?id=mnBqQgAACAAJ | year=1987 | isbn=9780521346825 | publisher=CambridgeUP |ref=none }} (Paperback reprint of 1982 edition)
* {{citation | last=Cairns-Smith | first=Alexander Graham | title=Seven Clues to the Origin of Life | url=https://archive.org/details/sevencluestoorig00agca | isbn=9780521398282 | publisher=Cambridge University Press | year=1990 | url-access=registration |ref=none }} (Canto reprint of the original 1986 edition)
* {{citation | last=Cairns-Smith | first=Alexander Graham | title=Evolving the Mind: On the Nature of Matter and the Origin of Consciousness |url=
▲ | title=Evolving the Mind: On the Nature of Matter and the Origin of Consciousness |url=http://books.google.com/books?id=WCCZEO3ZL04C
==See also==
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==External links==
* [https://web.archive.org/web/20120218065807/http://www.chem.gla.ac.uk/~bobh/agcs.html Academic website], [[University of Glasgow]]
* [http://originoflife.net/cairns_smith/index.html A bibliography of Cairns-Smith's origins of life publications], [http://originoflife.net originoflife.net]
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