"mineral evolution" (fwd)

[Michael Richard]

Here's an different take on that phrase:

Cairns-Smith

http://en.wikipedia.org/wiki/Graham_Cairns-Smith

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In simplified form, clay theory runs as follows: Clays 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 theory' 
of abiogenesis has not been widely accepted. Richard Dawkins uses it as an 
example in his 1986 book The Blind Watchmaker -- it was current and 
fashionable at that time.

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