Bjoern raised several questions. >< mark his text, (DC) my replies.
>The central ideas of the talk were the testability of a scientific (or any) claim, the lacking fossil record, and consequently the flaws in the macro-evolutionary parts of the theory of evolution. Michael Behe and Michael Denton, among others, were quoted as authoritative sources, and the former’s mouse-trap analogy was presented.<
(DC): As Denton has apparently modified his views, it's necessary to specify which of his books is being touted as authoritative.
The definition of macroevolution in this context is also problematic. As used by ID or YEC advocates, it basically means "evolution I do not believe in" and so the presence or absence of fossil evidence would depend on the particular aspect of evolution in question.
>This experience spurts some comments and questions.
>First, is it a fact that the ID movement has succeeded in bringing the neoID argument out to the grass roots of Evangelical America? How is that, and could ASA learn from that? <
(DC): The intensive publicity efforts of ID advocates and the relative compatibility or confusability with YEC and certain noisy atheists make general ID claims an easier sell than detailed scientific work from whatever background (including
ID, e.g. claiming that Behe proves ID versus actually knowing details of his claims).
> From my conversations with the students here it seems that the only viable option for connecting science and theology is the ID thing. Would that be true for other evangelical seminaries as well? Nevertheless, I just can’t help to ponder why the ID argument should be the best thing to do for an evangelical Christian. Is this due to any specific theological assumptions, or is it just the alleged advantage the argument gives the Christian apologetic?<
(DC):Having just visited Gordon College, I found the biologists and the Dean of Chapel dubious about ID; I do not know about the views at the somewhat associated seminary or of other groups at Gordon.
>Second, with regards to the testability of ID and science in general I won’t bother the list (as I think this was duly debated a few months ago), and so goes for Behe and Denton. But I have a problem with the fossil record argument. Because I’m not a scientist I can’t deal with the issues of the empirical data of evolution on standing foot, and my general question is therefore: What is the true (or truth approximate) status of the fossil record corroborating the claims of the theory of evolution? I guess this question demands a very long and complex answer, but I hope that there is something like a short version of an answer. Most often this argument is posed so that the reliability or truth of micro-evolution doesn’t entail the reliability or truth of macro-evolution, and while the fossil record that verifies the reliability or truth of macro-evolution is insufficient, the argument goes, macro-evolution simply can’t be reliable or true. The argument also incidentally direc!
ts attention to the transitional forms in the fossil records, or the transitional forms that should have been there, and lays out in detail how it is nearly impossible for a fish-like animal to evolve into a bird-like animal (apologize my unscientific terminology). <
(DC):Three major factors determine the quality of the fossil record: the abundance of the organism, the durability of the organism, and the preservation potential of its environment. Something that is common, with a tough skeleton, and living in shallow marine habitats is likely to have a very good fossil record, and we can probably trace its evolutionary history quite well. On the other hand, a soft-bodied organism found on a single mountain peak is almost certainly not going to be fossilized. Thus, the degree to which the fossil record provides evidence on the evolution of a particular group is quite variable. The evolution of vertebrates and mollusks is generally quite well documented by fossils; the evolution of worms and mushrooms is generally documented only by molecular evidence and comparative morphological studies. This highlights one of the errors in the argument-if the fossil evidence is truly insufficient, this means that the fossil record is insufficient t!
o provide evidence, and evolution is neither confirmed nor denied. Molecular evidence suggests universal common descent, and various morphological features point to common ancestry and evolutionary changes, so the fossil record is not the only source of evidence for evolutionary patterns.
As noted above, the definition of macroevolution is problematic. As used by ID and YEC advocates, it tends to mean no common descent above a certain taxonomic level. Some YECs try to justify this by invalid, Platonic interpretation of the use of “kind” in the Bible; others simply draw some arbitrary level. The only concrete definitions that I have encountered have been either the assertion that every species is specially created or that the boundary is around the family level. In practice, the purported boundary between microevolution and macroevolution seems to vary with the degree of familiarity with the organism-humans are set apart, though the exact line drawn between human and other varies; family level is OK for mammals; and invertebrates are generally ignored. Special creation of species is untenable in the light of the numerous new species and occasional genus observed to arise within the past century, either in nature or in the lab. Nevertheless, it is popu!
lar. I have even had an engineer tell me that Darwin’s Black Box supports the special creation of species. The evolution of higher taxa, such as families, orders, classes, phyla, and kingdoms, is less suitable for observing in action for two reasons. First, such taxa are defined on the basis of major differences, which are likely to reflect the accumulation of several individual mutations over a long period of time rather than one huge mutation one afternoon in lab. Recognizing major differences is mostly by hindsight. An alien biologist checking out the earth in the late Devonian would probably have considered the earliest amphibians to be just a weird variety of lobefin fish. Secondly, for something novel to succeed, there must be a niche available for it. Not counting human-caused extinctions, the last major extinction was 65 million years ago. Most of the major options are already taken, so a dramatically new type of organism is unlikely to meet with success. Ho!
wever, experiments on fruit flies have produced individuals that do no
tera) or even of insects (Class Insecta) by mutating genes in charge of taxonomically important features. True flies have two (or rarely zero) wings; the hind wings are reduced to knobs used for balance, but lab mutations have produced four-winged individuals. Insects have six legs and two antennae; they apparently derive from crustaceans with many pairs of legs and two pairs of antennae. Thus, mutant fruit flies with legs rather than antennae represent a reversion to a very primitive level of arthropod evolution.
Transitional forms require a bit of defining as well. It is highly unlikely that we will actually discover the fossil remains of the very individual that gave rise to a later population. More likely, we might have a third cousin twice removed, or perhaps the great great great great grandson of the third cousin, whose family stuck with the intermediate morphology while the direct lineage continued to evolve into the new form. Thus, if we define transitional forms as individuals showing characteristics of both the ancestral and descendant form and thus reflecting a major evolutionary transition, there are plenty of these. On the other hand, a transitional form strictly defined as the direct ancestor itself is probably impossible conclusively identify. By defining transitional form in the latter way, a paleontologist can readily get himself widely quoted in the YEC literature as an authoritative scientist declaring that transitional forms do not exist. However, the former!
definition is both closer to the popular understanding and what is relevant for the truth of evolutionary continuity. Transitional forms are likely to be somewhat rare. Although the occasional YEC caricature as a mix and match assortment of fully-developed parts is grossly inaccurate, it is true that a transitional form will have something of a mix of features. As a result, it is not going to be particularly effective at competing with either the ancestral form or with the descendant form. For example, the earliest amphibians would not have been as good swimmers as the fishes. They were much better crawlers than fish, but not nearly as good as later amphibians, who also were able to get out on land. Thus, the very primitive amphibians would probably become extinct as more advanced amphibians developed. Furthermore, stability is often a good thing evolutionarily-if it ain’t broke, don’t fix it. Many organisms show extensive periods of little change, punctuated by bri!
ef spurts of variability. Unless someone collects the right layer and
documentation of the transition.
Nevertheless, there are some quite good transitional forms. Within the vertebrates, the jawless fishes and conodonts represent intermediate levels between other chordates and the jawed fishes. The hagfish and lamprey have managed to survive to the present while retaining this primitive condition by finding specialized niches. Several evolutionary transitions can be observed, including changes in the amount and structure of the armor, and body streamlining and modification of the tail for better swimming. Within the bony fishes, the primitive lobefins have limb bones and teeth similar to those of the early amphibians; lungs and other adaptations to breathing air also appear relatively early in this group. Other amphibian-like features appear within the lobefins over time; for example, a recently-found specimen from Pennsylvania is a fin with both fish-like rays and tetrapod-like toes. The earliest amphibians retain many fishlike features, including lateral lines (sense !
organs functional only in water), flattened tails, etc. The transition from amphibian to reptile is gradual enough that there is some uncertainty as to where to draw the line-determining the kind of egg that a fossil hatched out of is quite difficult. Reptile to mammal transition is again well-documented. The distinguishing mark of true mammals has been arbitrarily drawn at the point where a reptile-like jaw joint is replaced with a mammal-like joint, but even this official dividing line is a bit fuzzy (like the skin of the advanced mammal-like reptiles) because there are some early mammals with a double jaw joint. The first mammal-like feature to appear is a particular configuration of the skull bones. Before too long, the teeth began to have greater variation. Other mammal-like features then appear in this lineage, even indirect evidence suggesting the presence of milk, fur, and high levels of metabolism. The reptile to bird transition likewise has some good transit!
ional forms, though also some gaps, as expected for fragile terrestria
t about any taxon with a decent fossil record, and even some with generally poor records but with fossil soft-bodied transitional forms in the Cambrian. Mollusks are particularly good, with their durable shells. Also, as the group I study, their transitions are the most familiar, but they are hardly the main topic of YEC and ID claims.
Estimating probability for any transition is an exercise in hand waving. We do not know exactly what mutations were necessary nor the probability of any given mutation nor what alternative mutations would have given an equivalent result.
Some arguments against transitional forms are semantic tricks rather than scientific claims. These typically depend upon an Aristotelian insistence on dividing middle terms. E.g., Archaeopteryx is either a bird or a reptile. Therefore it is not a transitional form. Of course, the uncertainty of which category to place it in actually reflects its transitional status, so this argument is self-defeating, if carefully analyzed.
A few of the YEC anti-transitional form arguments are simply fictions based on idle speculation. Scott Huse, in The Collapse of Evolution, wants to know where are the prized reptile-bird transitional fossils, half scaled and half feathered. A trip to a local park with bread crumbs would reveal that modern pigeons have scales on their legs. Similarly, the “textbook” It Couldn’t Just Happen claims that amphibians could not evolve from fish because fish have gills and amphibians have lungs. Many fish, including those most closely related to amphibians, have lungs; many amphibians have gills or else get by without lungs or gills, and every year millions of tadpoles and young salamanders successfully make the transition between gills and lungs.
Other aspects of evolution besides transitional forms are also reflected in the fossil record. Primitive organisms with comparable potential for fossilization appear before more advanced forms. The oldest known fossils are bacteria. Later, primitive eukaryotes appear, followed by more advanced forms such as algae. The oldest animals clearly assignable to a phylum are sponges and cnidarians, two of the most primitive phyla. Next come relatively generic representatives of more advanced phyla, and then generally increasing specialization. Meanwhile, the plants invade the land and advance from liverworts through club mosses and ferns to conifers and flowering plants.
Dr. David Campbell
"Old Seashells"
Biology Department
Saint Mary's College of Maryland
18952 E. Fisher Road
St. Mary's City, MD 20686-3001 USA
dcampbell@osprey.smcm.edu, 301 862-0372 Fax: 301 862-0996
"Mollusks murmured 'Morning!'. And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!
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