Re: DNA

"Val Mirov" <val.mirov@[EMAIL PROTECTED]
> wrote in message 
news:1118049730.446516.32660@[EMAIL PROTECTED]
>> THe first self-replicators didn't very likely have DNA at all, or many
of
>> the more complex structures of a modern cell.
>
> Oh Yeah? How do you figure that out? Try driving your car without an
> engine.

Don't sneer until you know something about a subject: it makes you look
like 
an asshole.

People who actually want to know about the possibilities concerning 
replication without DNA or cells might like to start with Dr. A. Graham 
Cairns-Smith's controversial 1985 book, 'Seven Clues to the Origins of 
Life'. The book popularized a theory he had developed since the mid-1960s,

that a simple intermediate step between inanimate matter and organic life 
might be provided by the self-replication of *clay crystals in solution*.

In simplified form, his '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. M***** 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.

Katt.