Friday, May 17, 2002
Archaeopteryx is often touted as evidence that dinosaurs' scales eventually became modified to become feathers, and thus that evolution from reptiles to birds is a feasible idea. However, there are a few questions about this that I'd like to have answered before accepting this idea.
There were two groups of dinosaurs: saurischia (lizard-like, and including things like Triceratops, Stegosaurus, and pretty much all the dinosaurs that walked on four feet) and ornithischia (bird-like, and including Velociraptor, Tyrannosaurus rex, and most of the dinosaurs that walked on two legs). Now, the idea behind Archaeopteryx is that a member of ornithischia modified over time and eventually became a bird. There's a problem, however. Ornithischia doesn't have the right anatomy to give rise to birds. Saurischia does (or at least has a closer one). Archaeopteryx is definitely an ornithischid, and lacks a sternal keel for anchoring the bulky muscles necessary for flight. It also doesn't have the wishbone-shaped pelvis common to birds (which saurischia does possess). Even more important, it doesn't appear that archaeopteryx was anywhere close to flying or even gliding. Its back feet were best suited for running along the ground, not perching in trees as would be necessary. Now, saurischia does appear to have many of the anatomical features to possibly give rise to birds. However, we haven't seen any saurischids remotely resembling birds, casting doubt on the possibility that they did in fact do so. I also wonder why no reptiles since have developed feathers, if the variation was common enough back then to allow a new class to develop. This is certainly not conclusive proof against macroevolution, but I do think that these questions are worth being answered before accepting theory as fact.