WRITTEN BY: RAYMOND TALLIS | APPEARS IN: ISSUE 46
POSTED BY: TPM ⋅ JULY 23, 2009 ⋅ EMAIL THIS POST ⋅ POST A COMMENT
FILED UNDER SCIENCE
Ray Tallis argues that there is no evolutionary explanation of consciousnessWe have grown accustomed – perhaps too accustomed – to the idea that every characteristic of living creatures has been generated by the operation of natural selection on spontaneous variation; that it is there because it has, or at the very least once had, survival value or was a consequence of other things that had a survival value. Consciousness, even human consciousness, we are told, is no exception to this rule. Biology does not tolerate anything biologically useless and, given that my brain consumes 20% of my energy supply, and quite a lot of this seems to be used by neurones that are supposed to be responsible for keeping me conscious, consciousness must have a use. And it follow from this that all the things that consciousness enables us to get up to – not only fleeing predators whom we are aware of but also creating art or writing books like The Origin of Species – must also be directly or indirectly related to survival – now, or at some time in the past. Whether or not this is true, the ubiquity of “neuro-evolutionary” accounts of everyday human life is a testimony to belief in the power of evolution to explain consciousness.
But how well-founded is this belief? Was it really natural selection that eventually brought into being creatures that could see that they were naturally selected? Was it the blind laws of physics that so organised the matter in us that it could see the laws of physics and that they were blind? If we are going to address these questions properly, we need to start far enough back to see them clearly. We need to ask by what means consciousness could have come into being – if it was not there in the beginning - and what advantages it confers.
The zero point of evolution is a primitive self-replicator, perhaps a silicate, hardly differentiated, though exquisitely structured, like a crystal. A succession of steps over huge stretches of time, and unconsciously guided by natural selection, led to single cell organisms with their nuclei, organelles, membranes and, eventually, one or two bits of kit such as flagella to aid swimming. That was the story of life for 2.5 billion years until the Cambrian explosion 500 million years ago. Then multi-cellular forms arrived; after which came more complex organisms, with distinctive organs and systems, to deal with the business of keeping the organism stable, accessing nutrients, evading predators, and - when sexual reproduction came on the scene to give natural selection more genetic variation to get its teeth into - finding mates.
The confidence that these developments can be explained in Darwinian terms seems increasingly well-founded; so let us set aside the Creationist appeal to “irreducible complexity”, as evidence that higher organisms could not have evolved step-by-step, and the related claim that Intelligent Design is required to explain the emergence of exquisite structures such as the eye. But what of the other great story: the emergence of sentience, and of more complex consciousness, and ultimately of self-consciousness? How well does this fit into the Darwinian picture?
Very badly, notwithstanding Richard Dawkins’ claim that “Cumulative selection, once it has begun, seems…powerful enough to make the evolution of intelligence probable, if not inevitable” (The Blind Watchmaker p.146). Consider vision: let us begin with the notional “ur-eye”, the light-sensitive spot on the skin of some ancestral creature. This might confer a tiny survival advantage, perhaps making it easier to avoid predators. And one could see how an ever more complex sensitive surface, wiring the organism into ever more exquisitely discriminated and versatile behaviour, might be explained by natural selection. There are now very good accounts of gradual changes, each conferring an advantage, leading to the emergence of the orbit, the retina, the lens and so on, without appealing to Intelligent Design. And there are plenty of intermediate forms, demonstrating the benefits of having photosensitive structures marking the staging posts to the kind of complex eyes seen in higher organisms. But this story doesn’t address three problems that a satisfactory evolutionary account of consciousness would need to deal with. Consider the emergence of sight from photosensitivity.
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NOTA DESTE BLOGGER:
Tallis é um filósofo e médico ateu:”I am a humanist and see my work as a doctor and as a philosopher as respectively an expression of, and as setting out the case for, my humanist convictions.”
Fonte.
