The Failures of Mathematical Anti-Evolutionism
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The Failures of Mathematical Anti-Evolutionism (Jason Rosenhouse) (z-lib.org)
(Moorhead and Kaplan 1967, 96)
We now move on to the statements made by Waddington and Medawar. Johnson would have you believe they responded to Ulam’s insightful mathematics by refusing even to consider it, demanding that evolution be taken as an unassailable starting point. In reality, their remarks came in the discussion after Ulam’s presentation, and 4.4 the perils of long-term modeling 103 after the criticisms of his model just described had been raised. It was in this context that Waddington said: Could I put your question upside down? You are asking, is there enough time for evolution to produce such complicated things as the eye? Let me put it the other way around: Evolution has produced such complicated things as the eye; can we deduce from this anything about the system by which it has been produced? One possible deduction would be that this thing worked by algorithms rather than by describing bits. … (Moorhead and Kaplan 1967, 28) This certainly does not sound like an expression of mindless dog- matism. It sounds more like Waddington is suggesting a potentially fruitful starting point for an investigation, one more likely to be successful than what Ulam put forth. Waddington and Medawar were simply putting into practice the principle we discussed in Section 1.3: If extensive physical evidence suggests that something occurred, but a simplistic mathematical model says it is impossible, then it is the model and not the evidence that must yield. Which brings us, finally, to Mayr’s statement. No one familiar with anti-evolution literature will be surprised that Johnson has omitted crucial context for understanding Mayr’s point. Johnson even shortened a sentence without giving any indication that he had done so. Mayr’s full statement was this: So all I am saying is we have so much variation in all of these things that somehow or other by adjusting these figures we will come out all right. We are comforted by knowing that evolution has occurred. (Moorhead and Kaplan 1967, 30) Had Johnson quoted the full sentence, his readers might have won- dered what Mayr meant by “we have so much variation in all of these things.” And that, in turn, would have required providing some further context. 104 4 the legacy of the wistar conference Here is that context: The statement I just quoted comes at the end of a very long speech by Mayr in the discussion after Ulam’s presentation. Mayr spoke for several minutes, uninterrupted. In this speech, he went through several of Ulam’s parameters and pointed to concrete reasons why it was so hard to assign numerical values to them. The parameters themselves, he argued, are influenced by so many other variables that they can take on wildly different values in different contexts. His point was twofold. The first was that Ulam’s model was just too simplistic to be useful for anything. The second was that, precisely because the relevant parameters are so numerous and variable, mathematics is not useful for answering a question such as, “Did evolution have enough time to produce an eye?” Summarizing, here is what actually happened at Wistar: Ulam presented a mathematical model for studying rates of evolution that, by his own repeated admission, was simplistic, not biologically realis- tic, and intended only as a starting point for discussion. The biologists then pointed out specific, concrete ways in which the model was unrealistic. They were able to do this so readily because of their familiarity with recent experimental work in this area and their immersion in the relevant theoretical concepts. They then suggested a better approach to devising a mathematical model for something like the evolution of the eye. This gives rather a different impression than that gained from Johnson’s account. I have belabored this discussion for two reasons. The first is that it is a specific example of a general phenomenon in anti-evolutionist literature: a complete lack of conscience about accurately presenting the views of their opponents. Johnson, you can be sure, had no interest in the technical minutiae of what was discussed at Wistar. Instead he just selected a few out-of-context phrases he could use for rhetorical effect and presented a highly distorted view of what happened, strictly for the purpose of making biologists look bad. This sort of thing is entirely standard among anti-evolutionists, which is one of the reasons scientists generally view them with such disfavor. 4.5 the two pillars of mathematical anti-evolutionism 105 The second reason is that it perfectly illustrates one of the themes of this book: distinguishing good mathematical modeling from bad mathematical modeling. There is a reason biologists do not engage in the sort of long-term modeling attempted by Eden and Ulam. Earlier, we said that mathematical modeling is the art of discarding most of reality, in the hope that what little remains is the really important part. Particularly in physics, this sort of thing is often possible. When seeking useful solutions to physical problems, it is often true that you only need to consider a small number of variables. In contrast, when you are studying the possible outcomes of millions of years of evolution, you need to keep all the variables. There is no useful mathematical model to be found because all the myriad variables are important. This was precisely Mayr’s point. He certainly was not saying that Darwinism is adhered to dogmatically as an unquestioned axiom. Instead he was saying something more like this: We have copious physical evidence that modern life forms are the end results of a lengthy evolutionary process. Since this implies the eye is the product of evolution along with everything else, we accept that as a working hypothesis. And since no mathematical model could possibly include enough of nature’s complexity to be convincing, we are not worried that a few back-of-the-envelope calculations will provide a good reason for abandoning that hypothesis. 4.5 the two pillars of mathematical anti-evolutionism The proceedings of the Wistar conference are sometimes fascinating and sometimes frustrating. There are moments of great lucidity and insight, but also moments where you feel people are talking past each other or failing to make important points. This is to be expected when reading transcripts of in-the-moment conversations, as opposed to polished papers. 106 4 the legacy of the wistar conference For me, the conference heroes were Ernst Mayr and Conrad Waddington. Mayr’s own presentation bore the witty title, “Evolu- tionary Challenges to the Mathematical Interpretation of Evolution.” It was a brilliant elaboration on the theme of what goes wrong in trying to devise long-term mathematical models for evolution. Waddington supplied an eloquent summary paper that presented the issues with a lucidity that had sometimes been lost during the formal presentations. They both participated in many of the discussions, and most of what they said was cogent and on point. For example, I had to smile when I came across this statement from Waddington’s summary paper at the end of the conference. Bear with me, since this is worth quoting in detail: I think what the biologist is saying in this connection is that we have a space of all possible nucleotide sequences with associated amino acid sequences, so that you have the DNA and the protein which you can consider as a complement. … This set was entered at the beginning of life, starting at some point or points and was explored to find sets which would operate adequately enough to ensure transmission. The space was explored to some extent, but always sequentially from the last position to some neighboring position. As soon as it was explored enough to get sufficient of these couples together to work with fair efficiency, they became insulated from the whole of the rest of the space … Therefore, life has only explored a minute fraction of the total nucleotide space. In the part which it has explored, which is the only part relevant to evolution, biologists are asserting that the meaningful section of it is quite large in comparison with all the things that could conceivably be made out of it in single steps. It is a much larger fraction than is the space of meaningful strings of English words. I think this is the point. We are asserting that it is a large fraction 4.5 the two pillars of mathematical anti-evolutionism 107 of the total space which could be made from the nucleotides involved, but still we are saying that the meaningful space is a minute fraction of the total nucleotide space. Download 0.99 Mb. Do'stlaringiz bilan baham: |
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