(continued . Subject: SWAA Lecture Date: 18 Jan 1993 16:25:42 GMT Dobzhansky's review summ

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(continued ... From: philjohn@garnet.berkeley.edu (Phillip Johnson) Subject: SWAA Lecture Date: 18 Jan 1993 16:25:42 GMT ) Dobzhansky's review summarized Grasse's central thesis succinctly: The book of Pierre P. Grasse is a frontal attack on all kinds of "Darwinism." Its purpose is "to destroy the myth of evolution as a simple, understood, and explained phenomenon," and to show that evolution is a mystery about which little is, and perhaps can be, known. Grasse was an evolutionist, but his dissent from Darwinism could hardly have been more radical if he had been a creationist. It is not merely that he built a detailed empirical case against the neo-Darwinian picture of evolution. At the philosophical level, he challenged the crucial doctrine of uniformitarianism, which holds that processes detectable by our present-day science were also responsible for the great transformations that occurred in the remote past. According to Grasse, evolving species acquire a new store of genetic information through "a phenomenon whose equivalent cannot be seen in the creatures living at the present time (either because it is not there or because we are unable to see it)." Grasse acknowledged that such speculation "arouses the suspicions of many biologists... [because] it conjures up visions of the ghost of vitalism or of some mystical power which guides the destiny of living things...." He defended himself from these charges by arguing that the evidence of genetics, zoology, and paleontology refutes the Darwinian theory that random mutation and natural selection were important sources of evolutionary innovation. Given the state of the empirical evidence, to acknowledge the existence of some as yet undiscovered orienting force that guided evolution was merely to face the facts. Grasse even turned the charges of mysticism against his opponents, commenting sarcastically that nothing could be more mystical than the Darwinian view that "nature acts blindly, unintelligently, but by an infinitely benevolent good fortune builds mechanisms so intricate that we have not even finished with analysis of their structure and have not the slightest insight of the physical principles and functioning of some of them." Dobzhansky disagreed with Grasse fundamentally, but he acknowledged at the outset that his French counterpart knew as much about the scientific evidence regarding animal evolution as anyone in the world. As he put it, Now one can disagree with Grasse but not ignore him. He is the most distinguished of French zoologists, the editor of the 28 volumes of Traite de Zoologie, author of numerous original investigations, and ex-president of the Academie des Sciences. His knowledge of the living world is encyclopedic. In short, Grasse had not gone wrong due to ignorance. Then where had he gone wrong? According to Dobzhansky, the problem was that the most distinguished of French zoologists did not understand the rules of scientific reasoning. As Dobzhansky summed up the situation: The mutation-selection theory attempts, more or less successfully, to make the causes of evolution acces- sible to reason. The postulate that the evolution is "oriented" by some unknown force explains nothing. This is not to say that the synthetic...theory has explained everything. Far from this, this theory opens to view a great field which needs investigation. Nothing is easier than to point out that this or that problem is unsolved and puzzling. But to reject what is known, and to appeal to some wonderful future dis- covery which may explain it all, is contrary to sound scientific method. The sentence with which Grasse ends his book is disturbing: "It is possible that in this domain biology, impotent, yields the floor to metaphysics." I began with the Dobzhansky/Grasse exchange to make the point that whether one believes or disbelieves in Darwinism does not necessarily depend upon how much one knows about the facts of biology. Belief that the various types of plants and animals were created by an extension of the kind of changes Dobzhansky's experiments brought about in fruitflies is at bottom a question of metaphysics. By metaphysics, I mean nothing more pretentious than the assumptions we all make about just which possibilities are worth considering seriously. For example, Pierre Grasse was willing to consider, and eventually to endorse, the possibility that the so-called "evolution in action" which the neo-Darwinists were observing is merely a variation within the limits of the existing genotype and not a source of genuine evolutionary innovation. To put the point in the language used by some contemporary biologists, Grasse proposed to "decouple macroevolution from microevolution." Such proposals havegenerally foundered on the inability to establish sufficiently credible distinctive macroevolutionary mechanisms. (For example, the widely publicized "new theory" of punctuated equilibrium turned out to be just a gloss upon Ernst Mayr's thoroughly Darwinian theory of peripatric speciation.) Grasse differed from the Darwinists in that he was willing to consider the possibility that science does not know, and may never know, how new quantities of genetic information have come into the world. From Dobzhansky's viewpoint, to consider such a possibility would be to give up on science. As Dobzhansky saw it, we already know a lot about how plants and animal populations vary in the everyday world of ecological time. Dog breeders have given us St. Bernards and dachshunds, laboratory experiments have produced monstrous fruitflies, mainland species have differentiated after migrating to offshore islands, and the ratio of dark to light peppered moths in a population changed when the background trees were dark due to industrial air pollution. To be sure, none of these examples demonstrated the kind of innovation that Grasse had in mind. In the absence of a better theory, however, Darwinists consider it reasonable to assume that these observable variations illustrate the working in ecological time of a grand process that over geological ages created fruitflies and peppered moths and scientific observers in the first place. By making that extrapolation Darwinists create a scientific paradigm which can be fleshed out with further research, and improved. For a critic to suggest the possible existence of some factor outside the paradigm is helpful only if he can also propose a research strategy for investigating it. To Dobzhansky, therefore, Grasse's insistence that the sources of new genetic information might be a mystery to our science was pointless and harmful to the cause of science. (continued in next message...)


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