LICAMELI@pucc.Princeton.EDU (Paul R Licameli) (10/30/89)
Someone posted an article about the inadequacies of the arguments in Michael Denton's book, _Evolution: A Theory in Crisis._ I read parts of the book a few years ago, and have some off-the-cuff comments to add from memory. Sorry I don't have the book to refer to as I write. I recall that Denton's specialty is supposed to be molecular biology, and the chapters of his book highlighting the supposed inconsistency of the evidence of molecular taxonomy with the theory of evolution were touted as the real linchpin of his arguments. (We all know that such evidence is used in classification of organisms, in the reconstruction of the history of biological diversification, and even as evidence for evolution itself if your audience is sophisticated enough.) I read those chapters and found them very unconvincing, showing a profound misunderstanding of the theory on the part of the author. What Denton shows, with detailed examples, is that if you compare the amino-acid or nucleotide sequence data for several members of one taxon with those of an outgroup member, you have a discrete measure of distance: the number of disagreements in the sequences. You find that the outsider is equidistant from them all, give or take one or two units. Then he crows that this refutes evolution, because if evolution happened we should expect to find that the supposedly primitive members of a taxon should be intermediate between the other members and the nonmember -- that an amphibian is closer to a fish than a reptile is, or some such example. When I read this, I wanted to shout, gad-DAMN it, Mike, go back to your freshman biology class and write one hundred times on the blackboard, CONTEMPORARY ORGANISMS ARE THE LEAVES OF A BUSH, NOT THE RUNGS OF A LADDER! As a matter of fact, this fundamental misunderstanding of just what the implications of evolution for taxonomy really are pervades his work; he claims much earlier in the book that evolutionary theory should predict linear chains -- not hierarchical bundles -- in the classification of _contemporary_ organisms. But it just ain't so. Any kind of true intermediate is between earlier and later organisms, not between contemporaries; a so-called "primitive" contemporary is just one that agrees with a distant ancestor in whatever phenotypic trait we are considering. Any biologist worth his salt knows this point of theory. Anyone who doesn't appreciate it misunderstands the claims of evolutionary theory and has no place trying to refute them. The reality is that the pattern of evidence he documents is exactly what the evolutionary theorist expects to find, assuming (caveat, yes, ASSUMING) that selectively neutral point mutations can and do occur continually in different lineages, regardless of their _adaptive_ history, and that different lineages have a common history of mutations until the time of their genetic isolation from each other. What would not sit well with evolutionary theory is the absence of a consistent clustering pattern from a large number of comparisons. Now certainly _Evolution: A Theory in Crisis_ -- coming as it does from a fellow not aligned with any overtly creationist group, but rather claiming to be led to his skepticism by the evidence of his own eyes -- has been valuable grist for the eager ICR mill. From what I can gather from reading some back issues of _Acts and Facts,_ their newletter, it seems that their debaters now tote this book along and have it at the ready in case any opponent brings up the topic of molecular homology. Now note: Denton's fallacious argument rests upon the very _perfection_ of the hierarchical classification of organisms, in all its manifestations, molecular, anatomical, or whatever. But in ICR literature predating his book, when the authors discuss molecules at all they spend their time documenting the minor anomalies that do crop up (such as the indication from cytochrome c that suggests that primates diverged from the rest of the placental mammals before the marsupials), the flaws in the consistency of molecular and other taxonomies. Is the real evidence against evolution the one or the other? They certainly never clarify it -- or need to -- for their audiences, and the poor bloke put on the defensive can't clarify things without getting technical. In conclusion, I submit that ICR's new secular hero doesn't know what he's braying about; and given the inconsistency of their past arguments with their present reliance on Denton, either the ICR folks don't either, or they are being quite dishonest. Paul R. Licameli P.S. There was some mention of S. J. Gould's comments on Denton -- I'm curious. Pointers?