| Charles Darwin, in the notebooks he wrote immediately after his Beagle circumnavigation, wrestled with the problem of consciousness: what place had it in an evolutionary world? How and when did it commence? What role does it play in the struggle for existence? Ultimately he gave it up as a ‘question too far’ and returned to the more tractable problems of evolutionary biology. The problem has not been solved from his day to ours. …If we say, [for example,] ‘redness’ or ‘sharpness’ or ‘itchiness’ is just how it is to be, or to ‘live through’, a particular cerebral state we may have got some little distance towards identifying the issue. But far from all the way. For we seem to be led back to Darwin’s questions. How far down the living world can we trace this ‘inwardness’? The evolutionary tree shows no discontinuities all the way down to the prokaryocytes. And beyond the prokaryocytes, the thoroughgoing evolutionist would insist, is the macromolecular chemistry of the pre-biotic ocean. Surely it is madness to conclude that molecules and atoms also have this ‘inwardness’? Some have argued that consciousness emerges ‘suddenly’, as a quantum leap. The best-known sponsor of this novel answer to Darwin’s question is the Oxford mathematician Roger Penrose. He argues, as many have done before him, that an explanation of consciousness is not possible within orthodox Newtonian science, the paradigm within which neuroscience is presently situated. He looks to new developments in our understanding of what matter ‘is’ and in particular to the counter-intuitive features of quantum mechanics. Penrose has set out his arguments in two valuable books, The Emperor’s New Mind and Shadows of the Mind. In both cases he argues that the mind is more than a computer, that it must involve other and as yet unknown principles. He argues that these unknown principles derive from the post-classical physics of quantum mechanics. In Shadows of the Mind he takes up Stuart Hameroff’s idea that microtubules are the most likely sites for large-scale quantum states to occur in the nervous system. Why microtubules? Both Penrose and Hameroff recognise that nerve cells and synapses are too large and complicated to exhibit quantum effects. It is argued, however, that microtubules and their associated water molecules may provide conditions in which quantum coherence can develop (cf. superfluidity, superconductivity). In particular, both Penrose and Hameroff draw attention to a controlling electron situated between the α- and β-subunits of the tubulin molecule. They point out that alterations in the quantum states of this electron lead to conformational changes in the tubulin subunits and that these are propagated along the microtubule. Microtubules are, of course, not confined to nerve cells but form the cytoskeleton of most cells in the animal body and are also to be found all the way down the scala naturae to protozoa such as Paramecium. Does quantum coherence occur in these cells also?... Some will think this a reductio ad absurdum, others will perhaps suspend judgement. …The virtue of ‘microtubular consciousness’ is that it helps account for the origin of consciousness in the living world. It answers, in other words, one of Darwin’s questions. It provides an avenue of escape from the even more vicious reductio of conventional panspsychists: consciousness at the level of atoms. | — C. U. M. Smith, Elements of Molecular Neurobiology, Appendix 1 | Indexes/08 |
1 comments:
Prokaryocytes and beyond, in-depth evolution will stick, polymer chemistry is the former marine organisms. Certainly crazy concluded that the molecular and atomic, also have this' mean '?
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