The Origin of Life - CrystalsCrystalsThis page is about crystals, and the possible role they played in the origin of life.I think that the process most likely to be responsible for the origin of life is the process of crystalisation.
A. G. Cairns-SmithThe idea that crystals were the first living organisms was first proposed - and eloquently advocated - by A. G. Cairns- Smith, the Scottish chemist.The idea was first publicly proposed in a paper in 1966. Several books about it followed:
By contrast, "Seven clues.." is a popular work - presented as a Sherlock Holmes mystery - and makes for an easy introduction to the idea. The theory was favourably mentioned in Richard Dawkins' "The Selfish Gene", 1976 (page 21-22), and in greater depth in Chapter 6 of "The Blind Watchmaker", 1982. See my page of references for more details.
IntroductionEssentially, the idea is that the first organisms were "naked replicators" - rather than cells. A search for the most suitable candidates for such replicators strongly suggests that clay minerals are the most likely players. Other carbon-based alternatives based on carbon compounds appear to be unattractive by comparison.The crystals would have grown using conventional crystal growth processes, and would have divided when mechanical stress causes them to break into pieces.
Information is replicated across the layers of crystals during crystal growth. Specifically, the fault structure, domain structure and cross-sectional shape are all copied.
When the crystal breaks, the information is exposed at the ends of both the resulting crystals. It is this information that forms the heritable information of the crystals, and acts as the basis for genetic evolution. Physical aspects of the crystal acted as the phenotype - and caused selection to choose between different genotypes. Prominent targets for selection would have included brittleness, weight and speed of growth. Also, the surface grooves of the crystal would have played a role in catalysing reactions among other compounds in the solution. More information about how information storage in a crystal can take place is available here. Heredity in crystals appears to be a simple, natural and common occurence. Consequently, crystals appear to be the most obvious and plausible self-replicating agents in a pre-biotic environment. Crystals grow best in a solution which is just super-saturated. On another page I describe why these conditions arise frequently. If the correct conditions are present, crystal growth enjoys a form of natural error correction. This is the only type of error correction known to occur naturally outside of modern biology. The resulting high fidelity with which crystals can transmit information between their layers makes them the most obvious and natural candidates for the first living organisms.
TakeoverIf our ancestors were crystals, how come our genes are not crystalline?The answer to this question involves a genetic takeover. More information about genetic takeovers can be found here. The transition to cellular, nucleic acid-based life can only have happened a considerable time after the origin of life. Cells and nucleic acid represent high-technology devices that are extremely unlikely to have formed by chance - and consequently must have been constructed by an evolutionary process based on existing lifeforms.
NeglectCairns-Smith's work appears to have been neglected in modern times. Most books on the origin of life cite his work in their first chapter - point out the lack of any evidence supporting it - and then continue to other matters.For example, Paul Davis (in The Fifth Miracle) states: "It has to be said that there is very little experimental evidence to support Cairns-Smith's clay theory." (p.117). J. Maynard Smith's cursory treatment in The Major Transitions in Evolution is also fairly typical. He says: "Heredity has not been convincingly demonstrated". I have a page devoted to why I think the neglect has happened, and what the prospects are for doing something about it - here.
CriticismA page of criticism of the theory is available.
The most plausible theory - by farCairns-Smith's theories remain by far the most plausible account of the origin of life I've ever encountered. The extent to which his ideas have been neglected appears almost tragic. I believe his work should receive much more serious attention - and expect that it will eventually become the accepted theory of life's origin.The reasons for Cairns-Smith's rejection of "protocells" and organic materials (as described in "Genetic Takeover") remains instructive reading today.
Modern significanceThe theory has very significant implications for modern attempts to create living organisms from inorganic materials. If Cairns-Smith is correct, creating primitive evolving physical systems may be fantastically simple - and indeed they may even be forming continuously all around us.Certainly - even if we ignore his theory of the origin of life - Cairns-Smith's work is of pivotal importance - because it indicates a mechanism by which genetic takeovers may occur in established living systems. As life may shortly be facing the first genetic takeover for billions of years, this theory has a special relevance today.
ReferencesFor a page of references to Cairns-Smith's theories see here.
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