Before I was born, my dad turned down a chance to do graduate study at Harvard. He mentioned this to me a few years ago and said that while he now regrets not having taken the opportunity in one sense, if he had done so he would not have met my mother and therefore wouldn’t have his children and thus he’s glad he didn’t. And I told him that while I’m certainly very glad to be alive, if he had gone to Harvard he would likely have met someone else, had other children and would now love them as much as he loves me — and would be just as convinced that this alternative outcome was the best possible thing that could happen.
This is the concept of contingency and it is one that has long been misunderstood by intelligent design advocates, as biologist Joe Thornton pointed out in a letter to Carl Zimmer a couple years ago.
The letter concerned research he has done on the evolution of molecules, retracing the mutations that made them what they are today. ID creationist Micheal Behe, after initially downplaying the research, ultimately argued that it supported ID. It didn’t. And Thornton points out the way that IDCs confuse contingency with improbability.
Thanks for asking for my reaction to Behe’s post on our recent paper in Nature. His interpretation of our work is incorrect. He confuses “contingent” or “unlikely” with “impossible.” He ignores the key role of genetic drift in evolution. And he erroneously concludes that because the probability is low that some specific biological form will evolve, it must be impossible for ANY form to evolve….
Finally, Behe erroneously equates “evolving non-deterministically” with “impossible to evolve.” He supposes that if each of a set of specific evolutionary outcomes has a low probability, then none will evolve. This is like saying that, because the probability was vanishingly small that the 1996 Yankees would finish 92-70 with 871 runs scored and 787 allowed and then win the World Series in six games over Atlanta, the fact that all this occurred means it must have been willed by God.
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.
And this is precisely the problem with creationist probability arguments much of the time.