And according to Barbara Stahl, in Vertebrate History: Problems in Evolution, (pp. 349-350) "how [feathers] arose initially, presumably from reptiles scales, defies analysis...It seems, from the complex construction of feathers, that their evolution from reptilian scales would have required an immense period of time and involved a series of intermediate structures. So far, the fossil record does not bear out that supposition."

Mr. Poling:

And it is unlikely to. Skin impressions only fossilize under certain rare conditions. We have no idea whether the Dinosaurian lineages considered to be closely related to birds had feathers or not. Indeed, to my knowledge there are no skin impressions of such Mammals as the Sabre Toothed Cat or Dire Wolf. Based solely on fossil and skeletal evidence, how do we know those two animals didn't have feathers? Taking this analysis further, there are no skin impressions from the majority of fossilized birds. Based solely on this fossil and skeletal evidence, how do we know they had feathers? I don't much care for trying to use feathers as a method to debunk evolution when we can't even tell that fossil birds had feathers and fossil mammals had hair.

Indeed, this goes right back to the idea of the fossil record not showing intermediate structures in the evolution of feathers. The fossil record doesn't even show, in most cases, creatures we know had to have feathers had feathers. Also, it appears that the period of time some think necessary to derive feathers is being used against the theory of feather evolution. Let's say, for the sake of argument, that birds did indeed evolve from Dinosaurs. Let's also say, for the sake of argument, that the lineage that would eventually evolve into birds started down that road at the very dawn of Dinosaur evolution. The first Dinosaur appears in the late Triassic, 235 million years ago. The first bird shows up in the Mid Jurassic, 166 million years ago. That gives feathers 70 million years to evolve. Whether this is sufficient time for feathers to evolve in the hypothesis of Barbara Stahl, I do not know. "Immense" could mean just about anything.

Addendum:

Natural selection can happen quickly, in extreme cases as rapidly as a few years. Assuming one physical change, in the populations of animals leading to birds, every ten years, there were 7,000,000 changes in the physical characteristics of scales, protofeathers and avian feathers between the evolution of the first dinosaur and of Archaeopteryx. If the fundamental structure of feathers, protofeathers, or true feathers of a morphology different from modern avian feathers were present in the first dinosaur (as discussed below), then there were 7,000,000 refinements to structures that had already been evolving for tens or hundreds of millions of years.

Mr. Buckna:

Another question for Darwinists to ponder is: how could scales become feathers, and not only be useful in the intermediate stages, but provide a comparative advantage?

Mr. Poling:

How could hair not only be useful in the intermediate stages, but provide a comparative advantage? Two types of animals have evolved hair in the history of the planet: mammals and pterosaurs. Undoubtedly the hair of mammals and pterosaurs are different chemically and arose independently, yet they still arose. Why? Insulation, most likely. It is therefore not unlikely that feathers could evolve for the same reason. They may have begun as an insular covering, and as dinosaurs moved into the trees more uses were found. There's been a thread discussing this very question on the Dinosaur Mailing List for several weeks. Message count is probably around 200 or more ... which means there's a large number of different possibilities discussed for the rise and then specialization of feathers.

Addendum:

Mr. Buckna appears to be using a rather popular argument among creationists and anti-evolutionists, that avian feathers are good for flight and flight only. Another way they may phrase the same argument is that avian flight is impossible without feathers and feathers are good only for flight, therefore both birds and feathers must have been created simultaneously. The problem with this argument is that avian feathers are not good only for flight:

• Avian feathers are incredible insulators (who has not owned a down-filled winter jacket at some point in their life?). It is very possible that feathers began their evolutionary trek as insulatory structures. Large non-avian dinosaurs, like large mammals, probably did not need much insulation. Small, warm-blooded dinosaurs would have needed insulatory structures even during the warmer Mesozoic, just as the small, warm-blooded mammals of the time likely did. This is especially true of those non-avian dinosaurs that lived on Antarctica, Australia and northern North America, close to the poles. It is not, then, a long leap of logic to hypothesize that dinosaur insulation took the form of feathers or something similar.

  It should be obvious to the reader that warm-bloodedness would have given all dinosaurs a great advantage over the cold-blooded reptiles and possibly cold-blooded non-mammalian therapsids. Any structure that would allow dinosaurs to maintain their body heat with lower energy cost would have given them an even greater competitive advantage. As a purely insulatory structure, feathers, protofeathers or "hair" would have been incredibly advantageous.

• Avian feathers are incredible display structures, especially in terms of colors. These structures allow the birds to attract mates and to serve as threat display to rivals, and in rare cases act as camouflage when the flora is also extremely colorful. Shape also can play a part, as it does in peacocks. As reptiles, birds have superior color vision compared to mammals, and any structure capable of superior color display would very likely become set in the population through sexual selection, regardless of its other advantages. Non-avian dinosaurs, with the same superior color vision, may also have used such structures for display purposes.

• Avian feathers are incredible camouflage. Not only can feathers be brightly colored to advertise the presence of the animal, they can be dully colored and/or take on patterns to break up the shape of the animal and hide its existence. Although many small non-avian dinosaurs may have had the kind of camouflage we see on birds today, larger dinosaurs may have had a completely unique camouflage, perhaps like that of World War II merchant ships that, while gaudy, broke up their lines and made them hard to spot at sea. Any camouflage that hid non-avian dinosaurs from predators or prey would be a definite advantage.

The most likely scenario is that the selective pressures outlined above acted in concert in shaping avian feathers. Dinosaurs were and are incredibly diverse, coming in all shapes and sizes. It is very likely that very early in their evolution, non-avian dinosaurs took to the trees. This arboreal lifestyle may have caused the exaptation of their insulatory or display/camouflage structures into insulatory, display/camouflage and flight structures, the avian feathers we know today.

Perhaps falls from trees selected those animals with structures that slowed their fall (the usefulness and comparative advantage of this should be obvious). The fundamental structure may have evolved directly because of this or, more likely, was already present when non-avian dinosaurs took to the trees and changed as needs changed. If the shape of the feathers played a part in display or camouflage, it is possible that the feathers already had a shape that slowed the fall, thus allowing the bearer to survive and pass that characteristic on to offspring. After many generations, the airfoil shape we know today was set, giving avian dinosaurs the ability to quickly and safely transport themselves wherever they could thrive, an incredible evolutionary advantage.

This is only one scenario. It is possible that something entirely different occurred. The fossil record is annoyingly mute on the subject, providing no evidence (or only a single instance, if Sinosauropteryx turns out to be feathered) for the true evolution of avian feathers. There are several possible reasons for this.

The fossil record is biased toward large animals. Large bones are more likely to survive to be fossilized than small bones. If you were to count every bone laying on the ground on the continent of Africa, most of the bones you would find would be of large animals. Studies have been done to test this hypothesis, and indeed, in the test areas, nearly all the bones found were of large animals. The thousands of small animals were not represented by the bone clutter. Similarly, only a very small percentage of small animals are represented in the fossil record.

Just as there are hundreds of species of small animals today, it is likely that there were tens or hundreds of thousands of species of small dinosaurs over the course of their reign. Small, arboreal non-avian dinosaurs likely gave rise to birds. Because of the bias in the fossil record, the likelihood of finding fossils of any of them are slim. To make matters worse, forest environments are terrible places for fossilization. And the nail in the coffin is the fact that hair, feathers and other soft, fine body parts are preserved only in unique and rare circumstances where the preserving matrix is incredibly fine grained. Although we may find a few more non-avian dinosaurs like Sinosauropteryx with featherlike structures, it is unlikely that an arboreal non-avian dinosaur that just happened to flop out of its tree to be transported to a preservat-lagerstatte environment (one that preserves fine detail) will ever be found.

Mr. Buckna:

In his book "Evolution: A Theory in Crisis" (Adler & Adler, 1986) molecular biologist Michael Denton blows out of the water any notion that scales could evolve into feathers, given a million years, a zillion years, take your pick, since the structures of scales and feathers are ENTIRELY different. Jeff, have you ever seen pictures of scales and feathers taken with an electron microscope?

Mr. Poling:

The STRUCTURE of scales and feathers being different doesn't mean diddly. They have two entirely different uses and are therefore unlikely to have similar structures. If you look at diamonds and graphite under an electron microscope you'll see two entirely different structures ... yet they are both made exclusively of carbon.

The question, then, is whether reptilian scales are chemically and genetically similar to feathers. The answer is ... no. However, don't jump for joy because it is not as simple as that. The genetic markers in the DNA for growing scales are in precisely the same spot in both birds and, say, crocodiles. However, there is an extra set of genes in birds that have been shown to control the formation of feathers which crocodiles, obviously, lack. So it is obvious that feather growth is controlled differently and separately from scales. So the question remains: are they similar chemically?

The answer is: it depends on what scales you are looking at. The chemical makeup of feathers is different than the chemical makeup of scales, although you can find the chemical makeup of feathers in, say, crocodilian scales, and vice versa, although not in a significant degree. If you look at one of the two types of scales on a *bird*, the scutes, they *are* chemically identical, as are the structures of the claw-sheathes and the beak. The chemical makeup of feathers is dissimilar to the second type of scales on birds, which cover the bottoms of the feet ... with the complication that these scales are chemically, and, as discussed above, genetically, identical to reptilian scales.

These facts raise many questions. Birds have reptilian scales. They are chemically and genetically identical. Is this further evidence of a reptilian ancestry?

Scutes, claw-sheathes and beaks are chemically identical to feathers. Are scutes, claw-sheathes and beaks derived from feathers, or are feathers derived from scutes, claw-sheathes and beaks?

Dinosaurs also had claw-sheathes, beaks and scutes. Bird scutes being chemically identical to feathers raises the question, asked above, whether feathers could have derived from scutes. If so, the fact that dinosaurs had scutes could be further evidence for dinosaurian ancestry for birds. I guarantee that paleontologists would give their eye teeth to know the chemical composition of dinosaurian scutes.

Addendum:

To say Denton's opinions on the evolution of feathers "... blows out of the water any notion that scales could evolve into feathers" is an exaggeration to put it mildly.¹ Dr. Denton presents several theories for the evolution of avian feathers and points out some of the flaws in each. Dr. Denton also makes several arguments against these theories, several of them compelling in the context of the theories presented, most of them much less so.

The problem with Mr. Buckna's use of the book is that it was written over twelve years ago. In the intervening years, theories on the evolution of feathers in general, not just avian flight feathers, have been greatly refined, dropped, or new theories developed based on new evidence. Most of what Dr. Denton presents in his book is out of date with little relevance toward modern evidence and theories. The most glaring example of this is that Dr. Denton spends a considerable amount of time presenting theories for and arguments against feather evolution from reptilian scales. As discussed above, science no longer considers feathers to have developed from reptilian scales as we know them today, but from some hairlike structure that itself may have evolved from a second type of scale unknown today or some similar structure.

Although feathers likely did not evolve from reptilian scales but from some other unknown structure, the contention that they could not have bears examination.

Here is a picture of a bird foot. Note the scales, called scutes, on the foot and tops of the toes. These are the scales that are chemically similar to feathers. The other scales on birds, the ones chemically similar to crocodile scales and controlled by the same DNA sequences as in crocodiles, are out of sight on the bottom of the foot.

(For those who are not familiar with bird and dinosaur anatomy, I should point out that this picture is only the foot and not the entire lower leg. Birds and dinosaurs are digitigrade; they walk only on their toes, not the entire foot like humans do. The joint in the top left of the picture is, therefore, not the knee but the ankle.)

For a modern example of how one structure can be exapted into another structure one only has to look at mammalian hair. In humans, hair comes in many shapes, sizes and consistencies such as head hair, eyebrow hair and the hairs inside the nasal cavities. Nail is comprised of the same materials that make up hair, and could be considered another form of hair. The most extreme example of different types of hair belongs to the pangolin.

At right is a link to a picture of a pangolin. Click on the thumbnail image to view the picture. Click on your browser's "back" button to return.

As can be clearly seen in the picture, the pangolin, a type of anteater found in Asia and Africa, is covered with large, stiff scales.² These are not true scales in the reptilian sense as found on birds, lizards or even armadillos,³ but are actually highly modified hairs.⁴ If hairs can be exapted into scales in a "short" period of time (it is unlikely their evolution started before the "Age of Mammals" began 65 ma ago), then scales being exapted into feathers is not so incredible a thing.

What is even more interesting is an experiment by Zou and Niswander that suggests the opposite may be true: perhaps the scutes of avian and non-avian dinosaurs evolved from feathers! In the experiment, the scientists injected a virus into the limbs of various animals that blocked a certain set of proteins that cause the webbing between the toes of amniote embryos to disappear in later developmental stages. In addition to preventing the loss of the webbing, the virus had the unintended effect of embryonic chickens growing feathers in place of scutes.

As discussed on page 3, DNA evolution usually involves adding new sequences that modify or switch off the effects of old sequences. When the actions of these new sequences are interfered with, the characteristics from the old DNA are expressed. In the case of this experiment, blocking these proteins suggest that the primitive state of scutes is feathers; or, put another way, scutes evolved from feathers.

If avian dinosaur and non-avian dinosaur scutes are homologous, this suggests that all theropods with scutes carried the genetic capacity for feathers. Further, if theropod, sauropod and predentatan scutes were homologous, then feathers could have been a characteristic of all dinosaurs (George Olshevsky suggests that the arrangement of ankylosaur scutes generally shows the same pattern as that shown by developing embryonic feathers). Finally, if the scutes of primitive archosaurs were homologous with dinosaurian scutes, then not only did dinosaurs carry the genetic capacity for feathers, but so did pterosaurs and so do crocodiles today! Given that pterosaur "hair" has been likened to the shafts of feathers, this is a very intriguing hypothesis.

It should be noted that "feathers" in the discussions above does not specifically mean modern avian feathers. One of the sad results of the announcement that the structures of Sinosauropteryx are not modern avian feathers is that far, far too many reporters and members of the public take that to mean they could not be feathers (or protofeathers), period. Modern avian feathers are highly adapted for flight. True feathers on a non-flying organism, especially one that split off from the dinosaur lineage of birds before the evolution of avian-style flight, would likely look very different, perhaps like the hairlike feathers of the Kiwi.