Graham Cairns-Smith
Encyclopedia
Alexander Graham Cairns-Smith (born 1931) is an organic chemist and molecular biologist at the University of Glasgow
, most famous for his controversial 1985 book, Seven Clues to the Origin of Life. The book popularized a hypothesis he had developed since the mid-1960s, that a simple intermediate step between biologically inert matter and organic life might be provided by the self-replication of clay crystals in solution. He was disenchanted with the other ideas about chemical evolution
including the Miller-Urey experiment
and the RNA World.
Cairns-Smith has also published on the evolution
of consciousness
, in Evolving the Mind (1996), favoring a role for quantum mechanics
in human thought.
s form naturally from silicates
in solution. Clay crystals, as other crystals, preserve their external formal arrangement as they grow, snap and grow further. Masses of clay crystals of a particular external form may happen to affect their environment
in ways which 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 at random in other streams. Thus by simple, inorganic, physical processes, a selection environment might exist for the reproduction of clay crystals of the 'stickier' shape.
There follows a process of natural selection for clay crystals which trap certain forms of molecules to their surfaces (those which enhance their replication potential). Quite complex proto-organic molecules can be catalysed
by the surface properties of silicates
. The final step occurs when these complex molecules perform a 'Genetic Takeover' from their clay 'vehicle', becoming an independent locus of replication - an evolutionary moment that might be understood as the first exaptation
.
Despite its frequent citation as a useful model of the kind of process that might have been involved in the prehistory of DNA
, the 'clay hypothesis' of abiogenesis
has not been widely accepted. As it was current and fashionable at that time, Richard Dawkins
used it as the example model of abiogenesis in his 1986 book The Blind Watchmaker
.
biochemistries and presented some evidence to support this possibility in a paper for a biological research journal in 1975.
University of Glasgow
The University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...
, most famous for his controversial 1985 book, Seven Clues to the Origin of Life. The book popularized a hypothesis he had developed since the mid-1960s, that a simple intermediate step between biologically inert matter and organic life might be provided by the self-replication of clay crystals in solution. He was disenchanted with the other ideas about chemical evolution
Chemical evolution
Chemical evolution may refer to:*Nucleosynthesis, the creation of chemical elements in the universe either through the Big Bang, or supernovae*Abiogenesis, the transition from nonliving elements to living systems...
including the Miller-Urey experiment
Miller-Urey experiment
The Miller and Urey experiment was an experiment that simulated hypothetical conditions thought at the time to be present on the early Earth, and tested for the occurrence of chemical origins of life. Specifically, the experiment tested Alexander Oparin's and J. B. S...
and the RNA World.
Cairns-Smith has also published on the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
of consciousness
Consciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
, in Evolving the Mind (1996), favoring a role for quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
in human thought.
Clay hypothesis
In simplified form, the clay hypothesis runs as follows: ClayClay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s form naturally from silicates
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...
in solution. Clay crystals, as other crystals, preserve their external formal arrangement as they grow, snap and grow further. Masses of clay crystals of a particular external form may happen to affect their environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
in ways which affect their chances of further replication — for example, a 'stickier' clay crystal is more likely to silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
a stream bed, creating an environment conducive to further sedimentation
Sedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
. 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 at random in other streams. Thus by simple, inorganic, physical processes, a selection environment might exist for the reproduction of clay crystals of the 'stickier' shape.
There follows a process of natural selection for clay crystals which trap certain forms of molecules to their surfaces (those which enhance their replication potential). Quite complex proto-organic molecules can be catalysed
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
by the surface properties of silicates
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...
. The final step occurs when these complex molecules perform a 'Genetic Takeover' from their clay 'vehicle', becoming an independent locus of replication - an evolutionary moment that might be understood as the first exaptation
Exaptation
Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour...
.
Despite its frequent citation as a useful model of the kind of process that might have been involved in the prehistory of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
, the 'clay hypothesis' of abiogenesis
Abiogenesis
Abiogenesis or biopoesis is the study of how biological life arises from inorganic matter through natural processes, and the method by which life on Earth arose...
has not been widely accepted. As it was current and fashionable at that time, Richard Dawkins
Richard Dawkins
Clinton Richard Dawkins, FRS, FRSL , known as Richard Dawkins, is a British ethologist, evolutionary biologist and author...
used it as the example model of abiogenesis in his 1986 book The Blind Watchmaker
The Blind Watchmaker
The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design is a 1986 book by Richard Dawkins in which he presents an explanation of, and argument for, the theory of evolution by means of natural selection. He also presents arguments to refute certain criticisms made on...
.
Extraterrestrial biochemistry
Smith suggests that the ancestors of humans might have had alienExtraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...
biochemistries and presented some evidence to support this possibility in a paper for a biological research journal in 1975.
Selected publications
- Cairns-Smith, A. G. (1968) An approach to a blueprint for a primitive organism, in: Waddington, The Origin of Life: Towards a Theoretical Biology, volume 1, pp. 57–66.
- Cairns-Smith, A. G. (1982) Genetic Takeover and the Mineral Origins of Life, Cambridge University Press, New York, ISBN 0-521-23312-7 (1985 reprint).
- Cairns-Smith, A. G. (1985) Seven Clues to the Origin of Life, Cambridge University Press, New York, ISBN 0-521-27522-9.
- Cairns-Smith, A. G. (1996) Evolving the Mind. On the Nature of Matter and the Origin of Consciousness, Cambridge University Press, New York, ISBN 0-521-40220-4.
External links
- Academic website, University of GlasgowUniversity of GlasgowThe University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...
- A bibliography of Cairns-Smith's origins of life publications, originoflife.net