Monday, October 19, 2009

The Probability Of Evolutionary Pathways

Joe Thornton of the University of Oregon and the Howard Hughes Medical Institute writes these thoughts about how to understand and appreciate the probability of evolution following one specific pathway among many possible:

Consider the future: there are countless possible that could emerge from our present state, making the probability of the one that actually does evolve extraordinarily  low.  Does this mean that the future state that will ultimately emerge is  impossible?  Obviously not.  To say that our present biology did not evolve  deterministically means simply that other states could have evolved instead; it does not imply that it did not evolve.

Consider your own life history as an analogy.  We can all look back at the road  we have traveled and identify chance events that had profound effects on how our lives turned out.  “If the movie I wanted to see that night when I was 25 hadn’t been sold out,  I never would have gone to that party at my friend’s house, where I met my future spouse….”  Everyone can tell a story like this.  The probability of the life we actually lead is extraordinarily small.  That obviously doesn’t mean that its historical unfolding was impossible.

That we inhabit an improbably reality requires a divine explanation only if we, like Behe, take the teleological view that this is the only reality that could exist.  But if we recognize that the present is one of  many possibilities, then there is no difficulty reconciling the nature of  evolutionary processes with the complexity of biological forms. As history unfolds, potential pathways to different futures are constantly opening and  closing. Darwinian processes are entirely adequate to move living forms  along these pathways to a remarkable realization – but just one realization out of many others that could have, but didn’t, take place.

Beautifully written.

The entire article is worth reading as it explains how complex traits with interlocking components can evolve through a combination of natural selection and random genetic drift acting on adaptive mutations and neutral intermediates. And this is not just theory. Joe Thornton leads a team that does experiments to show how this can happen. The article encapsulates modern evolutionary thinking about the evolution of complexity quite well.

That it is a devastating put down of the arguments made by the Intelligent Design community makes it especially pleasurable to read. 

No comments:

Post a Comment