Evolutionary purpose September 26, 2010

I am really interested in how our minds work. Not having a background in neuroscience, neurobiology, or neuro-anything for that matter, I'm currently limited to reading lighter material on the subject until my understanding goes deeper. I've read books that cover the social side of how our minds (fail to) work (e.g. The Drunkard's Walk) and some that are more technical (but still light) such as How We Decide and On Being Certain.

At the moment I'm reading Seeing Red: A Study in Consciousness. In it Nicholas Humphrey, the author, aims to present an evolutionary purpose for consciousness which he argues is independent of perception. At one point in the book Humphrey writes the following regarding sensations: It is fair to assume the capacity has been designed in by natural selection.

I take issue with the assumption. I've always had a problem with this approach to reasoning about any single element of a species. Why must everything be 'designed in' by natural selection? It seems just as likely to me that any given attribute we or any other species posses could simply be a side effect of some other positive attribute which actually was 'designed in' by natural selection.

To be clear, my issue is not with the notion of human evolution specifically favoring sensations. A number of reasons come to mind in support of this point of view. My problem is really the order of the reasoning. To say that 'This attribute exists, therefore it must have an evolutionary purpose' seems absurd to me. I find it hard to believe that random genetic mutations are so delicate as to change only one thing at a time or that natural selection is so precise to weed out everything except the bare minimum needed to win.

Unless I'm missing something fundamental with evolution and natural selection, I suspect that Humphrey only presented his reasoning in this order for dramatic effect.  After all, it is his stated goal to give an evolutionary purpose to consciousness.

However, it's still disconcerting how often I see that logic being used to reason about how we got in our current evolutionary state. It seems to be quite common among these light-neurosciency books I've been reading.

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