Some brief notes from his lecture at the San Diego Museum of Natural History, 11/29/04
by Casey Luskin
On a night when I should not have taken a study break from finals (11/29/04), I heard Dr. Alan Feduccia (evolutionary biologist and chair of the Biology Dept at University of North Carolina, Chapel Hill) speak at the San Diego Natural History Museum on the origin of birds. Feduccia is a committed evolutionist but he is well known because of his rare views among evolutionist paleontologists that birds did not evolve from theropod dinosaurs. Some of his views are unorthodox, some are not. But none of his views were without evidence to bolster his claims. The lecture was well-attended as the San Diego Natural History Museum has had an extensive fossil exhibit on the origin of birds for some time. I was invited to attend by a friend who is former IDEA Club leader who currently works at the museum.
To begin, I'd like to highlight some of the main points he made during his talk:
Until the late 1960’s, Feduccia says many thought Archaeopteryx was a feathered dinosaur. Many paleontologists said Archaeopteryx showed flight evolved in a "ground-up" fashion, meaning that the first birds evolved from land-dwelling dinosaurs. But many from the ornithological world felt something was wrong with that story. In 1980, Feduccia was putting together a book on birds, which included a chapter on bird origins. But after analyzing the claims that birds came from theropod dinosaurs, Feduccia said he felt like he was being asked “to put a round peg in a square hole.”
Feduccia was critical of drawings of Archaeopteryx done by Gregory Paul. Paul drew Archaeopteryx as a small dromaeosaur. But Archaeopteryx wasn’t cursorial—it was arboreal. It didn’t have a vertical pubis, so Feduccia says Paul drew it wrong.
Feduccia asked in particular why a terrestrial creature would have a reversed toe which is a feature for sitting on branches? Feduccia has correlated the curvature of bird claws to behavior. Flatness of claw tells if it is ground-dwelling but Archaeopteryx had a curved claw, indicative of perching behavior, and possibly suited for climbing tree trunks. Feduccia said computer tomography has found that Archaeopteryx has a brain and ear-canals similar to modern birds. In terms of wing-loading, Feduccia found Archaeopteryx falls right in the center of modern birds. Finally, looking at feather shape has shown that Archaeopteryx was a good flier. Asymmetry in feathers can tell you how well a bird flies. Feduccia firmly believes that Archaeopteryx is nothing short of a modern-like bird because it had an elliptical wing and asymmetrical feathers. Secondarily flightless birds have symmetric feathers. This, and many other features cited by Feduccia indicate that Archaeopteryx was an arboreal bird that was a good flier. Yet, he pondered, it is still drawn by some as a cursorial dinosaur-like creature.
Feduccia recounted how cladists strongly emphasized the claims that birds arose from theropods. Cladistics is essentially a statistical analysis comparing characteristics in various organisms, which then are used to structure hypotheses about ancestry. But Feduccia says that cladistics is incapable of dealing with convergent evolution, which he believes is “very prevalent” in vertebrate history, particularly with regards to the origin of birds. Feduccia gave some examples of where cladistics fails. It will put aquatic reptiles like mosasaurs with other ones that are not related at all. Within modern birds, Feduccia notes that those who construct phylogenies based upon cladistics place loons and grebes as closely related because of certain similar characteristics which are bioechemically and embryologically distinct. In particular, the “cnemical crest”—a swimming adaptation—is very similar in grebes and loons but they are formed totally differently embryologically.
One of the main criticisms made by Feduccia is the claim that it is possible for flight to develop from the ground-up. He asked what selective advantage feathers would have for running? He noted that some have cited pre-adaptation because it has been claimed feathers were useful for some dinosaurs as an insulatory pelt or for heat radiation in hot-blooded dinosaurs. But feathers are not only finely tuned for flying, they are energetically and embryologically costly to produce. Feduccia observed that feathers are the perfect aerodynamic structure. They’re strong, light, asymmetric, produce slotting wings, and are like Velcro in that they can return back to their original position. Plus they’re waterproof. Essentially, he said they’re the most complex structure ever to grow out of vertebrate skin. He calls them the “perfect” aerodynamic structure for flight and yet supposedly they evolved for endothermy! Feduccia doesn’t buy it. He says that for facilitating endothermy they are no better than hair which is much simpler and much less biologically costly. Once you’ve evolved feathers for endothermy you must explain how they would elongate on the wings. Feduccia noted that many evolutionists claim feathers elongated to catch insects—but Feduccia said feathers really aren’t very good for that and it again is a stretch to claim a structure so well-suited for flying and poorly suited for catching insects evolved for the latter, and not the former. Essentially, feathers are very very embryologically costly, very good for flying, and not exceedingly good at anything else. Feduccia is skeptical that feathers would have arisen for a purpose other than flight. In a moment of levity, Feduccia showed a slide of fossils which exhibit the beginnings of ground-up flight, and the slide was blank.
Feduccia also commented on Confuciousornis, which Feduccia (like most others) believes is a true bird. Feduccia was critical of those who have called it an earthbound dinosaur, such as what he called “Unscientific American.” He noted that it has the foot of a kingfisher and is incapable of significant ground activity. Ornithologists say it was a tree-perching bird. Furthermore, like Archaeopteryx, it had curved claws, indicating an arboreal lifestyle.
But what about all those alleged "feathered dinosaurs?" Feduccia divided them into two categories—those with dino-fuzz, and those with true feathers which have a central rachis and branching barbs. Sinosauropteryx had dino-fuzz. According to Feduccia, Dinofuzz need not have anything to do with the origin of true feathers. Feduccia says dinofuzz was very similar to many collagenic fiber structures found in other fossil organisms such as icthyosaurs, pterosaurs, ornithischian dinosaurs, and fossils species. He even said some pterosaurs have such collagenic fibers which clearly are filamentous structures, but had nothing to do with feathers. He sees no reason to assume that the dinofuzz on theropods was any different.
Feduccia was skeptical of those who claimed that some dinosaurs had a downy-covering. He observed that some baby ostriches are covered in downy feathers, but if they get wet, if they are not quickly warmed by the mothers wings, can easily die of hypothermia. For a species to spend its time covered in such feathers would be extremely maladaptive.
Feduccia did cite one fossil organism he thinks had proto-feathers—Longisquama. Had “parafeathers” with a hollow rachis, and attached individually by papillae. He said it had a nice furcula, and thinks this could be the origin of feathers.
Because Feduccia rejects dinofuzz as evidence for the origin of feathers, he thinks that any true feathered dinosaurs would have to be pennaceous. The first evidence of such supposedly found was Caudipteryx in 1998. But Feduccia says Caudipteryx is simply a bird--it is not a feathered dinosaur. Firstly, its center of gravity is forward like the center of gravity in a bird. Secondly, its wing which is essentially that of a modern bird with feathers perfectly in place like a modern bird. However, he thinks that its features indicate that it is in the process of becoming a secondarily flightless bird. He claimed that if a modern-day emu (a flightless bird) were preserved in the Chinese deposits of that age, many paleontologists would mistakenly think they are feathered dinosaurs. For Feduccia, a major problem with the claim that Caudipteryx represented an intermediate between dinosaurs and birds is that it comes long after Archaeopteryx, and Archaeopteryx was already a true bird.
Feduccia thinks one “trump character” in the debate should be the digits on the limbs. Both theropod dinosaurs and modern birds have tridactyl (three-fingered) hands---for many, this has been said to solidify the link that birds came from such theropod dinosaurs. He noted that in all amniotes, digits emerge during development from a cartilaginous array. The part that turns into digit 4 is always the same, providing a reference point for numbering the other digits. Feduccia says that developmental evidence supports that birds fingers are numbers 2, 3, and 4. (Our thumb is digit 1, and our pinky finger is digit 5.) This claim has been confirmed by studies of ostrich development, where digits 1 and 5 can be seen as small stubbs which become reabsorbed, straddling what become the fully developed digits 2, 3, and 4. But fossil evidence has established that in theropod dinosaurs, their three-fingers are digit numbers 1, 2, and 3. As Feduccia put it, there is a “digital mismatch.” This is significant because Feduccia believes it would be very difficult to a trait like this to change or switch once it had evolved. Feduccia says development of a hand is very developmentally constrained. Once you are committed to developing digits 2, 3 and 4 switching to 1, 2 and 3 would be very dramatic. Feduccia concluded this provides strong evidence that birds cannot be descended from these theropod dinosaurs.
If digits are indicative of ancestry, and birds didn’t come from theropods, then from whence did they come? To find the ancestors of birds requires going back to a time before reptiles had committed to the “1-2-3” or “2-3-4” digit orientations. He says we must go back to the late Triassic or early Jurassic to find animals that haven’t committed to 1-2-3. Thus, Feduccia believes the origin of birds is ancient. There are also not fossils showing how birds could have evolved on this route, and so Feduccia is content to believe that many fossils are yet to be found.
Feduccia names a number of reptiles which are “uncommitted” in terms of their digits which could be possible candidates for the avian basal stock. But he cannot tell for sure which, if any, represent actual ancestors. Finally, Feduccia’s favorite specimen is Microraptor, because he thinks it supports the claim that avian flight evolved from the trees-down.