Re: Ch. 8 - Patterns and Processes of Biological Evolution
Sorry for the delay folks! I had loaned this one from the Library, and returned it after having took notes on each Chapter. But I lost my notes! Now I've got the book again, so now I can finally continue.
This chapter focuses on creationist arguments in regards to gaps in the fossil record, the Cambrian explosion, irreducible complexity, and the distinction between micro and macro evolution.
Darwin himself addressed a few of these arguments in his famed "On the Origin of Species", notably the argument of irreducible complexity and the argument about gaps in the fossil record.
Darwin's reply to criticisms based upon the lack of fossils are mirrored by the direct sources quoted in this book that debunk creationism. It is clear that very few life forms ever fossilize, so it is unreasonable to expect fossils for every creature that ever existed. The gaps in the fossil record are to be expected given our knowledge of fossilization. But the fact that the fossils we DO find accord with and support evolutionary theory is strong evidence that the theory is correct. This argument seems to partly hinge on the common misconception that the only way to "prove" evolution is to appeal to fossils, but this is hardly the case. Another reason we shouldn't expect to find "missing links" is for the simple reason that creationist ideas of what a "missing link" should look like are flawed. They suppose that the ancestor midway between humans and apes should appear half ape and half human, but the proportion need not be maintained in this manner, as evolution does not progress by standard amounts of change in consistent spurts. The reason we don't find missing links is even more obvious: because generally they have localized ranges. A species that is in the process of evolving to be better suited for a particular environment will not be able to fully inhabit that place until it has become totally specialized and is best suited to that environment. At that point, they spread out. This is why we may find fossils of the ancestor and the descendant, but not the missing links--because they would be confined to a more localized area, and it would thus be harder to find them.
As for the Cambrian explosion, the book does a wonderful job showing that the "explosion" is overhyped by creationists and they misleadingly assert that basically all these different types of creatures from entirely different animal kingdoms appeared overnight. However, it is obvious that evolution was happening for a long time prior to the explosion, and also that the explosion itself spans a very, very long time period spanning millions of years. The creatures found are also more interrelated than creationists make it appear.
Then, of course, there is Behe's famous argument of "irreducible complexity", which he applies to various organic structures, usually on a cellular level. Nevermind his specific examples, though--it is clear that his argument is highly flawed. For Behe, something is irreducibly complex if removing any part of it makes it unable to perform its current function--but evolving structures routinely change functions as they adapt to environments, so it is clear that evolution is compatible with Behe's version of irreducible complexity.
Finally, I'm sure everyone has heard someone say at least once in their lives that "micro" evolution is true whereas "macro" evolution is false. But this is just silly. Most of the evidence in support of the theory of evolution does wonders to support what creationists call "macro" evolution. The fact that we cannot observe it in the way we can observe minor variation (like we do with Darwin's finches) doesn't make it false. It only means we have to find indirect observations based upon evidence. We have this in abundance--just look at the transitional fossils we have found, the distribution of species (ancestors typically live near descendants), vestigial structures (implying they had a use in another evolutionary line), and so on.
At any rate, I found it difficult reading much of the creationist tripe in these chapters, but it was at least rewarding to be able to read the critiques issued by a real scientist afterwards. Although, I must say, these arguments aren't nearly as silly as the "Vapor Canopy" argument used in the previous chapter!