After all, from all of the above mentioned hypothesis and
experiments, to an extent, it was claimed that the organic components
for the origin of life was formed from the non-living matters in a
prebiotic conditions of the environment and atmosphere, and also
spatially claiming that the RNA was responsible for the storage of
genetic information instead of DNA. But still, it was not clear on
explaining about on how the polymerization of a RNA molecule and the
formation of membranes from lipids. The genetic sequences in RNA are
essentially instructions on how other molecules should be arranged in
proteins or how other molecules should be arranged. But it was not
clear that how the biologically inert matter helped in the evolution
of organic life and how the organic molecules were arranged in an
organized sequence. For these clarification, it was claimed by the
Clay Model Hypothesis which was proposed by Scottish Scientist,
Alexander Graham Cairns Smith in 1965.
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| Alexander Graham Cairns Smith |
The Clay Hypothesis postulates that complex organic molecules arose
gradually on pre-existing, non-organic replication surfaces of
silicate crystals in solution. The self replication of clay crystals
in solution might provide a simple intermediate step between
biologically inert matter and organic life. Montmorillonite, an
abundant clay, is a catalyst for the formation of membranes from
lipids and for the polymerization of RNA molecule. The clay minerals
of montmorillonite catalyze the formation of RNA in aqueous solution,
by joining nucleotides to form longer chains.
The clay hypothesis suggests how biologically inert matter helped the
evolution of early lifeforms that is; by the formation of clay
minerals naturally from silicates in solution. These clay crystals
has a property to preserve their external formal arrangement as they
grow, snap and grow further. 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 catalyzed by the surface properties of silicates.
The mineral crystals in clay could have arranged organic molecules
into organized patterns. When complex molecules perform a “genetic
takeover” from their clay “vehicle”, they become an independent
locus of replication which led to an evolutionary moment that might
be understood as the first exaptation that is a co-optional shift in
the function of a trait during the evolution of life.
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| Bart Kahr |
In 2007, an American chemistry professor, Bart Kahr done some
experiments using crystals along with his colleagues and concluded
that the crystals were not faithful enough to store and transfer
information from one generation to the next.
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