Joined: Jan. 2007
Wesley Elsberry writes: "However, the presence of the argument claiming that thylacine/wolf similarities represent a problem for homology, and thus evolutionary explanation, is confirmed both by the documentation of the proceedings and by notes from an attendee that I've now consulted."
Actually, I did not question the evolutionary explanation, but I guess that would spoil your story. Folks, I am really not your enemy here. I have no problem with evolution, in principle. My skepticism is with several of the evidential arguments. I came here asking for a justification/ defense of one of the most fundamental claims of evolution. My question was, how is it that similarities such as the pentadactyl pattern are such powerful evidence for evolution, in light of equal and greater levels of similarity in distant species, such as displayed in the marsupial and placental cousin species?
This was my question. There are many, many more examples of similarities that do not fit the common descent pattern. Why are those that can be fitted to the common descent pattern cited as such powerful evidence? Without some justification, this fundamental claim of evolution appears to be selective. Unfortunately, good justification is hard to come by. The vast majority of the responses simply avoided the question and made up their own.
For instance, Stephen Wells responded, "For starters, how about some discussion of dentition and skull morphology, with regard to the claim that the thylacine and the wolf have 'almost identical' dentition?" Where did that claim come from?
Jeannot responded, "So Mr Hunter, you think that convergence is somehow problematic for the theory of evolution? ... if you want to use convergence as an argument against the ToE, you'll have to prove that convergent evolution is impossible." This is a combination strawman plus shifting the burden of the proof. Deadman responded with another version of this strawman: "Should I throw up my hands now and shout "We've met our Waterloo, they [similar looking species] LOOK alike!?" He then pointed to some references (good background material but they don't answer the question).
Brightmoon responded: "is cornelius trying to say that thylacine anatomy is similar because of separate creation ?" Huh? Aardvark responded: "Are you trying to say that there is some kind of law preventing evolution from creating superficially similar animals?" No, I'm not saying that. I'm trying to find good justification for one of your claims. Wesley continued to avoid the question with this: "What you've left off, though, is the fact that the physical constraints that *define* the niche also will be perfectly straightforward explanations for why some changes will be favored (they improved differential reproduction) and others will be disfavored (they decreased differential reproduction)." Of course. Now, how about answering my question?
There were, however, a few answers to the question. N. Wells gave this answer:
"The important thing about the forelimbs of birds, bats, dogs, pterosaurs, pigs, moles, anteaters, dolphins, and so forth is that their differences overwhelm their similarities, but their similarities are deeper and are the result of common inheritance. In contrast, their similarities are in many ways far less than the similarities between golden moles and marsupial moles or between ‘flying’ squirrels and ‘flying’ phalangers, but the latter similarities are superficial and are appear not to have resulted from shared inheritance. Both sets of comparisons and contrasts provide powerful evidence for evolution."
Unfortunately the explanation that one type of similarity is "deep" and the other "superficial" isn't going to satisfy very many people. This explanation really just raises more questions. When I asked for details, he deferred to Deadman who did give an answer:
"Skin would appear to me to be far more susceptible to evolutionary change than bones and the bones of the two animals in question are distinct in regard to this gliding adaptation, no? Optima in relation to physical constraints in light of a common "bauplan" , eh? That common "bauplan" includes pentadactyly that is found throughout mammals and hence would carry a bit more "weight" , dont'cha think? By the way, if this post seems a bit muddled, it's because I just woke up and it's 5:30 AM"
This seems like a perfectly reasonable answer, as far as it goes. The problem is it is farily subjective. Do we really want to make one of the fundamental evidential claims for evolution contingent on an opinion about what might, and might not, be more difficult for evolution to accomplish?
The one other answer was given by Douglas Theobald: "The difference is simple. In one case we have structural similarity that has a functional explanation (wolves). In the other case, we have the much more puzzling phenomenon of structural similarity in spite of functional diversity (pentadactyl limbs). This latter problem is what common ancestry explains, quite elegantly. Hence it is this latter type of similarity that is evidence for evolutionary homology."
Yes, of course, the personal incredulity of evolutionists is well documented. This is the standard response, but appeals to personal incredulity hardly make for strong scientific evidence. Nor does it help when evolutionists mysteriously drop this incredulity when such instances arise in distant species where common descent cannot be summoned as the explanation. In these cases we are told there was a structural convergence where the functions differ.
What we have here are a vast number of similarities across the spectrum in biology, often arising via different genes and development pathways, and often showing up in distant species. Whereever possible, they are ascribed to common descent. Otherwise they are said to have evolved independently. So far so good. But the former do not qualify as particularly powerful, objective, evidence for evolution.