Overwhelming Annoyance: Pt 2

5 01 2007

As would be expected, my review of a post on Overwhelming Evidence here was picked up on by some of the readership over there. In my original post I said that the website filters out the comments of those in favor of evolution, but I removed it from the original post as this proved incorrect: some have been ejected in the past for one reason or another but the website does not immediately filter out pro-evolutionary comments. It was my mistake and I have corrected it on the previous post. I attempted to create an account and log in with OE, but I never received a confirmation e-mail so I am unable to post there, thus my responding here rather than over on the original website. In any case, someone named TRoutMac (a self described “Intelligent (Graphic) Designer”) had some things to say about my reply. After correctly calling me on my mistake, he says this:

“It strikes me that much of our taxonomy already does rely, however, on “what animals look like”. That is, all vertebrates are grouped together. All animals with scales are grouped together, all animals with feathers, etc. That makes sense, nothing wrong with that. But to the extent that we make our taxonomic structure reflect a bogus theory, that taxonomic structure is going to be wrong and will ultimately need to be revised to SOME extent.”

Current systematics goes far beyond simply what animals “look like,” and although some of the early grouping Linnaeus did based upon appearances have held up, others have not. Such was the problem with Panda bears and Koala “bears”. When I was in elementary school, I was told that Pandas and Koalas look like bears, but they are not actually bears. This made sense as far as the Koala went, it being a marsupial and not looking very much like a bear at all, but I couldn’t quite figure out why a Panda shouldn’t be considered an actual bear. Add to this confusion the Red Panda, an animal that shows some characteristics close to the Panda and others that are closer to raccoons. Genetic verification, however, has shown that Pandas are indeed bears and most closely related to the Spectacled bear, thus putting the Panda where it truly belongs. As for the Koala, as I mentioned in my previous post children often get confused because of the name and the arboreal, fuzzy nature of the marsupial so it is not enough to go on superficial appearances alone.

The commenter also mentions some vague categories, only one actually being correct. Yes, Vertebrata is a subphylum of Chordata, encompassing all groups that have a protective covering over their spinal cord (as well as other characteristics such as skulls, so all vertebrates also belong to the unranked group Craniata). This is a rather large grouping, encompassing everything from fish to amphibians to reptiles to birds to mammals, all carrying common characteristics inherited from basal chordates. The other groups are superficial groupings that don’t really have any bearing, as fish and reptiles and birds all have scales but are not classified closely together. The same would go for feathers, birds and some dinosaurs both exhibiting feathers but they are not one in the same (birds being derived from dinosaurs). Morphology can tell us a lot about a creatures evolutionary history, this is most certainly true, but it is not all there is to it and oftentimes genetic studies help to clarify associations. Remember, we are dealing with the products (although they are still changing) of evolution that has been going on for billions of years, todays members carrying a string of innovations inherited from previous generations, hence convergent evolution and variation can make things a bit difficult to discern so we can’t always rely on appearances (just as we can’t exclusively rely on genetics).

TRoutMac also says this about my writings:

“The author of that response made a huge leap of faith in concluding that just because there are certain, limited similarities between birds and reptiles that birds are then necessarily “related.” Balderdash. That’s just more Darwinist dogma based on wild presuppositions.”

The actual history of the evolution of birds is still one that is being uncovered, and I do admit that it is perplexing. Archaeopteryx lithographica is a late Jurassic bird (the earliest one we know of, although it has more dinosaurian characteristics than bird characteristics) and yet the late Cretaceous theropods from China (i.e. those coming out of Liaoning) seem to have more derived characteristics than Archaeopteryx does. What happened here? Some, like Gregory S. Paul, have suggested that some of these late theropods were secondarily flightless, branching off from the group that led to (or contained) Archaeopteryx, but such a history is still under much debate. The complete story has yet to unfold but say that there are only a few “limited similarities between birds and [dinosaurs]” is silly. It is helpful to look at the derived characteristics of birds today, yes, but inferring dinosaurian ancestry on foot scales alone would be foolish. Dinosaurs and birds share many features, two of the most striking to me being how the boot of the pubis (part of a Saurischian dinosaur hip) swings backward through the Mesozoic, taking on the bird-like hip structure we observe from the appearance of birds onwards and the semi-lunate carpal in someDromeosaurids, allowing for an open-shut or “flapping” type motion of the hands.

Although fossils don’t often give us clues about soft tissues, we are lucky in that the lung structure of theropod dinosaurs requires some skeletal differences that are nearly identical to those in birds, suggesting that these reptiles had systems of air-sacs similar to what we see in turkeys and other birds today. This is important, as it would mean that the unique lung system for birds potentially developed before they took to the air, the birds taking advantage of an earlier advancement of evolution present in the dinosaurs. You can have a look at a comparison of the bones suggesting this finding yourself here. Dinosaurs also seem to have some bird-like characteristics as far as nest-brooding and sleeping posture, involving more bird-like care of the young than crocodile-like. While the exact behaviors will likely never be known, we have fossils of Oviraptor brooding over their eggs and dinosaur nest fossils that suggest the young stayed in the nest for some time. It is important to note here the strongest evidence for post-hatching care comes from the Maiasaura, an Ornithischian (or bird-hipped) dinosaur, the group that did not lead to modern birds. This could mean that care of the young was a more common feature among all dinosaurs and not just common to theropods, although evidence for this is certainly lacking. Another curious fossil is that of Mei long (Chinese for “Dragon soundly sleeping), a troodontid found in a sleeping position akin to what we see in birds as a means of conserving heat. Some could argue that this is a taphonomical anomaly, the body arranged like this after death, but that seems highly unlikely as when dinosaurs decompose the head arches back like they’re trying to touch their nose to their tail, not nearly folded over in a sleeping position.

Like I said previously, the exact evolutionary history of how birds evolved is still very much a mystery, but this does not mean we are without any clues or data. Over and over again, every fossil we find relevant to this lineage points to the fact that birds evolved from reptiles and such a statement is not in dispute. Even those who disagree from most paleontologists and cladistic scientists like Fedducia still point to a reptilian origin for birds. If there is no connection, then why all these derived characters and odd things like birds with teeth and dinosaurs with feathers? Even if the argument is made that dinosaurs and birds are not related, Microraptor is still a dinosaur and would have to evolve all these bird-like characteristics (like feathers) from somewhere. I cannot honestly understand how anyone can look at these fossils and all the similarities between dinosaurs and birds and not come away with a sense of connection between the two (unless, of course, they already ascribe to an ideological agenda that would prevent such interpretation a priori).

TRoutMac finishes by asserting that I don’t know enough to refute Helena’s arguments about taxonomy and evolution, but I feel this is untrue. I may not be a published scientist yet, nor do I assert to know everything that every happened in evolutionary history (as you can tell from this post I try to admit when I don’t know something or have made an error), but I do understand enough to say that you can’t lump fish and reptiles together on the basis of scales or birds, bats, and insects together on the basis of flight or merely look at an organism and judge it by its appearance. This discussion has been based upon the discussion of charismatic megafauna, but what about the vast majority of life in bacterial and plant forms? How ludicrous it would be to classify bacteria by the way it looked or say that because two plants are similar, they must belong to the same group (classification of such groups, even by todays standards, still remains difficult). Our currently classification system may not be perfect, but it is open to readjustments and changes, always striving to get a more accurate picture of the interconnectedness of life and that interconnectedness then speaks to evolution. No one is saying “Well, you found a new fossil dinosaur with feathers that’s different and changes our idea of evolution, so you can either destroy it, change it, or shove it in somewhere that it does no harm to evolutionary lineages already in place.” Not at all. I’m tired of ID advocates invoking conspiracy or a religious-type attitude over something that is plain to see: evolution happens, but the theories explaining how it happens can change. If you really want to talk controversy, look into the battle going on about cladistics vs traditional classification; that’s where the real controversy is.




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