Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Life Before Life
Other theories focus on the replication mechanism, which doesn’t necessarily require organic matter to occur.
For example, the British chemist Graham Cairns-Smith argued that the first living beings were not carbon composts but clay crystals, i.e. minerals. He agrees with skeptics who think that the birth of the first cell is just statistically impossible (he calculated the probability of all the events required to create a DNA molecule and concluded that there wasn’t enough matter or time in the universe to achieve it). However, rather than invoking an external force, Cairns-Smith thinks that the most plausible explanation is in the other direction: life is not the towering accomplishment of Nature, but a mere leftover from something bigger that pre-existed. He compares it to some unlikely rock structures that can be found in natural parks: how could chance create such equilibrium-defying structures? They were actually part of a much bigger structure that crumbled to pieces. It was relatively easy for them to be created as part of the bigger structure. Now that the bigger structure is gone, they look surreal and unlikely. Ditto for life: Cairns-Smith believes that life is merely what is left of something that was much more likely to arise than a mouse or a bird. In his opinion, life is the remnant of a mineral process. Life's ancestors were self-replicating patterns of defects in clay crystals. One day those patterns started replicating in a different substance, carbon molecules. In a sense, Cairns-Smith wants to extend evolution to the pre-biotic world, to the world before life was born. (But these molecules are still purely self-replicating entities: it remains unexplained how they started growing bodies...) Basically, Cairns-Smith argued that evolution came first, and life came afterwards, as an accidental side-effect.
Synthetic self-replicating molecules that behave like living organisms have been crafted in the laboratory. The US chemist Julius Rebek ("Self-replicating system”, 1990) recreated artificially the principles of life postulated by the biologist Richard Dawkins: "complementary" molecules (ones that fit into each other by way of spatial structure and chemical bonds) and even self-complementary molecules.
The US chemist Jeffrey Wicken showed that the thermodynamic forces underlying the principles of variation and selection begin to operate in prebiotic evolution and lead to the emergence and development of individual, ecological and socioeconomic life. He treated the prebiosphere (i.e., the Earth before life emerged) as a non-isolated closed system in which energy sources create steady thermodynamic cycles. Some of this energy is captured and dissipated through the formation of ever more complex chemical structures. Soon, autocatalytic systems capable of reproduction appear. Living systems, according to his theory, are but "informed autocatalytic systems".
British biochemist Nick Lane pointed out that the "primordial soup" didn't have enough energy to start the chemical reactions necessary to produce life's chemistry. He argued in favor of life coming from the bottom of the ocean, in hot mineral-drenched waters. Natural gradients originate when these solutions cool down, and these gradients may have been the precursors of cell membranes.
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