g-rh@cca.UUCP (Richard Harter) (02/21/84)
This is a continuation of the enlightening and amazing discussion that Byron and I are having for the delectation of an enthralled net. Since I haven't saved either my original article or Byron's comments I cannot accurately reply to him. I shall resolve the problem by postulating a position for him and replying to that. (This is really no different than what most people on the net do and it eliminates repetitious quotation.) First of all, for those who were surprised by the line I put in about Archaeopteryx, I suggest that you read chapter 6 of "The Hot-Blooded Dinosaurs" by Adrian J. Desmond. If Desmond does not strike your fancy (being a sometimes debatable popularizer) I suggest you read Ostrom's letter to Nature -- Ostrom, J.H., 1973, The ancestry of birds. Nature, 242, p.136. To quote Desmond quoting Ostrom, "'Indeed,' remarked Ostrom, 'if feather impressions had not been preserved all Archaeopteryx specimens would have been identified as coelurosaurian dinosaurs.'" p. 205, Desmond. Chapter 6, entitled "A griffin rescues evolution", discusses in Archaeopteryx in detail. In particular, it is shown that (pp 209-211) that Archaeopteryx was capable neither of flying or gliding. Desmond also goes into the contention that Aves should be classified as a subclass of of Dinosauria. Kitcher (pp. 109) quotes Colbert (1980) in citing the essentially reptilian nature of Archaeopteryx. He claims, without discussion, that there are good reasons why fossilized flying forms are rare. He does not point out that there is a rather large gap between Archaeopteryx (mid Jurassic) and true bird fossils, e.g. Hesperonis (late Cretaceous) which flew (and had reptilian teeth.) To be fair, his main thrust is to show that Gish's treatment of the therapsid/mammal transition sequence is, ah, less than accurate. Nonetheless, Kitcher's treatment of Aves is dishonest. It simply is not known whether Archaeopteryx is ancestral to Aves. It is not known that the Coelurosaurians are ancestral, although it is plausible. It is not known when Aves originated. And, finally, no significant links in the supposed transition sequence have been found. Kitcher's book, incidentally, is not all that great. It has the following rather general faults: It is biased, hostile, and filled with rhetorical tricks. It lacks perspective, in that it neither gives a good overall picture of the creationist movement nor of modern evolutionary biology. I will grant that he does a nice hatchet job on selected arguments; on the whole, however, it is more heat than light. Consider a hypothetical reader who has a sparse knowledge of creationism and of modern evolutionary biology. On one hand, the reader is not given any real understanding of the real strengths of evolutionary biology; on the other hand he is left with a rather confused and incoherent picture of creationism. In short, I feel that Kitcher had too much fun grappling in the mud with his selected opponents and did a poor job of making his case. A rather more general objection that I have is that I don't think much of him as a philosopher of science. For example, consider the discussion pp50-54 (Darwin's daring). He claims that "The heart of Darwinian evolutionary theory is a family of problem solving strategies, related by their common employment of a particular style of historical narrative." He goes on to illustrate this concept with the tenrecs in Madagascar. Now it is all very well to say that Darwinian scenarios have great explanatory force, but are the explanations correct? In point of fact, we seldom know. The advantage of the scenarios is that they point out questions to ask. However, the fact that a particular sequence of events is plausible, given our current stage of knowledge, does not mean that it is correct or even a close approximation. More to the point, he does not differentiate very well between informed speculation and solid knowledge. For example, the therapsid/mammal transition sequence is fairly solid in that there is a well defined sequence of fossils with intermediate forms. In general darwinian scenarios and population dynamics are informed speculation -- we don't know enough about either what happened or about the underlying mechanisms. Byron quoted a number of passages from me at length which he commented on. To tell the truth, I found it rather hard to see any relevance between his quotations and his comments. Indeed I found it difficult to make much sense out of his comments. This, no doubt, is a failing on my part. However, I did gather the impression that he felt that the observation that there is a great deal that we don't know is a declaration that we shouldn't do science. This seems so peculiar a line of reasoning that I feel confident that I must have missed the full subtlety of his reasoning. In the event that he may merely be somewhat confused I will make the following observations. His first difficulty, as I see it, is that he doesn't distinguish between different kinds of scientific knowledge. It is convenient to distinguish between law, current fact, and past fact. The distinguishing feature of scientific law is that it is independent of time and place. Most of physics and chemistry has this character. It is the thing that makes experiments repeatable. It is also the real reason that it makes sense to talk about falsifiable theories. Current fact (e.g. descriptive astronomy, taxonomy) is a matter of observing and classifying what currently exists. Past fact (e.g. cosmology, evolution, archaeology) is the attempt to reconstruct what happened in the past. The reconstruction of the past is a matter of inference from current fact and from known law. In the nature of things it is a rather chancy business. To begin with, the current evidence is likely to be incomplete. Similarly, our knowledge of the governing laws is also incomplete. More subtly, the problem is always underdetermined. Finally, outside events must be considered. The latter point is frequently overlooked by people whose training is in the law end of science. An essential feature of a good experiment is that one arranges things to minimize the impact of outside events. As a result, outside intervention has no place in scientific law. On the other hand, it must be taken into account when we are attempting to reconstruct the past. This may take the form of giant meteors or nearby supernova exterminating the dinosaurs, black monoliths, or even supernatural beings. The key point is to ignore possible outside events which, in the nature of things, have no observable consequences. It is not that they couldn't have occurred -- we simply have no way to check on the matter. In contrast, there are outside events which are potentially checkable but which we are not at present able to check. Our tendency here is to prefer those which fit in most conveniently with our current reconstruction. For example, the case for abiogenesis is more convenient than compelling. Then there are situations where there is some evidence but it is incomplete. For example, one can make a respectable case that there the human mind is qualitatively unique and that this uniqueness is relatively recent, say 50 to 100 thousand years ago. (The case is scarcely compelling.) If this is true then one is strongly inclined to look for a causative event. Reconstruction of the past is a matter of possible pasts; the currently favored theory is likely to be out of favor tomorrow. For example, continental drift is now in and is thought to be well established. Planetary formation theory has wobbled all over the place. Man's family tree is rewritten every decade or so. It is of some importance to have a handle on what is known, and what is merely fashionable. The reconstruction of the history of life has a very mixed character. We know that the Earth is old. We know that there is a genetic unity to life. We have a paleontological record that records a succession of species. We also have a vast body of theory to explain the observed facts. There are really three theories of evolution. Theory I simply says that the physical and genetic continuity of life has not been broken. Theory II is the current reconstruction of the sequence of species. Theory III is the current theory of how species transform. Theory II wanders quite a bit for obvious reasons; theory III has problems which I have already discussed. Interestingly enough, theory I (upon which everything else hangs) has become much firmly based in the last thirty years. Now I conjecture that Byron feels that the (correct) observation that theory III is not well grounded is equivalent to a declaration that theory III is not science. I also conjecture that he feels that observing various inadequacies in theories II and III are equivalent to denying the validity of theory I. Finally, I conjecture that he is convinced that entertaining the possibility of conscious outside intervention is equivalent to accepting the literal truth of the Bible. No doubt, I have misunderstood him completely; however I have every confidence that he will be willing to instruct us on by errors. Respectfully submitted in the tradition of the Net Richard Harter