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Defending the Christian Worldview, Creationism, and Intelligent Design

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Defending the Christian Worldview, Creationism, and Intelligent Design » Theory of evolution » No evidence for the evolution of birds, feathers, and flight

No evidence for the evolution of birds, feathers, and flight

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Otangelo


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No evidence for the evolution of birds, feathers, and flight

https://reasonandscience.catsboard.com/t1694-no-evidence-for-the-evolution-of-birds-feathers-and-flight

It's ridiculous to think that birds "evolved" from reptiles. There are many features besides feathers that enable birds to fly. Their brains had to be modified for flight. Their bones had to have the hollow lattice as seen at present, and they had to develop special lungs that enable them to breathe deeply at every stroke of their wings. All of these structures, besides specialized development of the feather itself is necessary for a bird to fly. This coordination of characteristics makes the idea that all these flight features evolved randomly into the bird we see today profoundly absurd.

The anatomical placode in reptile scale morphogenesis indicates shared ancestry among skin appendages in amniotes 24 Jun 2016:
The fossil record lacks any evidence of intermediate forms (hence, of homology) between scales and hairs. In addition, hairs in mammals, feathers and feet scales in birds, and scales in reptiles exhibit substantial differences in morphogenesis. Finally, the presence and absence of β-proteins [a family of proteins unrelated to α-keratins ] in skin appendages of sauropsids (birds and reptiles) and in those of synapsids (mammals), respectively, only added to the confusion. All these considerations have, for decades, fostered the debate on the homology, or lack thereof, among these skin appendages and led some authors to conclude that homologous skin appendages do not exist beyond amniote classes (reptiles, mammals, and birds); that is, mammalian hair and avian feather would not have evolved from reptilian overlapping scales.
https://advances.sciencemag.org/content/2/6/e1600708

Take flying birds for example; suppose you aren't one, and you want to become one. You'll need a baker's dozen highly specialized systems, including wings, flight feathers, the specialized system which allows flight feathers to pivot so as to open on upstrokes and close to trap air on downstrokes (like a venetian blind), a specialized light bone structure, specialized flow-through design heart and lungs, specialized tail, specialized general balance parameters etc.

For starters, every one of these things would be antifunctional until the day on which the whole thing came together, so that the chances of evolving any of these things by any process resembling evolution (mutations plus selection) would amount to an infinitessimal, i.e. one divided by some gigantic number.

In probability theory, to compute the probability of two things happening at once, you multiply the probabilities together. That says that the likelihood of all these things ever happening, best case, is ten or twelve such infinitessimals multiplied together, i.e. a tenth or twelth-order infinitessimal. The whole history of the universe isn't long enough for that to happen once.

All of that was the best case. In real life, it's even worse than that. In real life, natural selection could not plausibly select for hoped-for functionality, which is what would be required in order to evolve flight feathers on something which could not fly apriori. In real life, all you'd ever get would some sort of a random walk around some starting point, rather than the unidircetional march towards a future requirement which evolution requires.

And the real killer, i.e. the thing which simply kills evolutionism dead, is the following consideration: In real life, assuming you were to somehow miraculously evolve the first feature you'd need to become a flying bird, then by the time another 10,000 generations rolled around and you evolved the second such feature, the first, having been disfunctional/antifunctional all the while, would have DE-EVOLVED and either disappeared altogether or become vestigial.

Now, it would be miraculous if, given all the above, some new kind of complex creature with new organs and a new basic plan for life had ever evolved ONCE.

Evolutionism, however (the Theory of Evolution) requires that this has happened countless billions of times, i.e. an essentially infinite number of absolutely zero probability events.

I ask you: What could be stupider than that?

http://www.veritas-ucsb.org/library/origins/quotes/macroevolution.html

"Feathers are features unique to birds, and there are no known intermediate structures between reptilian scales and feathers. Notwithstanding speculations on the nature of the elongated scales found on such forms as Longisquama ... as being featherlike structures, there is simply no demonstrable evidence that they in fact are. They are very interesting, highly modified and elongated reptilian scales, and are not incipient feathers."

Feduccia, Alan (1985) "On Why Dinosaurs Lacked Feathers The Beginning of Birds Eichstatt, West Germany: Jura Mus

As one Columbia University biologist put it, “ . . . we lack completely fossils of all intermediate stages between reptilian scales and the most primitive feather.”

http://cryptozoologynews.blogspot.com.br/2011/07/bird-fossils-reveal-lifes-colourful.html

Oregon State University, “Discovery raises new doubts about dinosaur-bird links,” June 9th, 2009, Physorg.com.

http://www.physorg.com/news163760732.html

The origin of birds has always been a major problem for Darwinism, and even today little agreement about the evolution of birds exists. One of the most difficult issues related to bird evolution is the evolution of feathers. Feathers are complex, designed structures required for flight, and are today found only on birds. A literature review on the evolution of bird feathers showed that even though feathers are found back as far as the Cretaceous, including many well-preserved samples in amber, the fossil record reveals a complete absence of evidence for feather evolution.

http://crev.info/2014/02/story-on-evolution-of-birds-glosses-over-details/

The beautiful Illustra documentary Flight: The Genius of Birds gives a much more elegant and satisfying explanation for flight, because it doesn’t gloss over the details, but accounts for all the traits needed for powered flight: efficient one-way lungs, efficient digestive and excretory systems, the beautifully engineered flight muscles that provide a compact center of gravity, the hollow bones, the navigation systems, the sensory components (able not only to see details from the air but to sense the magnetic field), the exquisite design of feathers, and the behaviors that allow birds to take advantage of air currents, including the lift from other birds in formation flight (1/16/14).  The integrated systems that allow an eagle to pick a fish out of a lake, a hummingbird (12/05/13) to hover in mid-air sucking its food out of a flower with a specialized nectar-trapping tongue, or a snowy egret with its large, elegant wings to fly between tree limbs without hitting them, are explained by appealing to what we know in our universal experience about complex functional systems.  Intelligent design is a known “vera causa” (true cause) that can account for the observations.

Evolution, by contrast, comes up empty looking for a true cause for flight (7/30/13).  Never do we see blind, unguided processes leading to complex functional systems with integrated parts contributing to the overall design goal.  Intelligent design is, therefore, the best scientific explanation in contrast to the storytelling from the Darwin camp (9/30/13).  The Tweety Rex fable looks downright silly by comparison.  With its high perhapsimaybecouldness index, its stretchable rates of evolution (a clear ad hoc theory rescue device), and its copious use of magic words (emerged, arose, developed, appeared), it reduces to “birds evolved because they evolved.”  If the public were allowed to hear the two explanations side by side, there would be no contest.  Darwin’s flightless DODO birds would go running out of the auditorium in shame.

http://able2know.org/topic/232172-1

Consider feathers, which come in more than one form. Down feathers serve for insulation and are not that much different from hair or fur. A proponent of evolution could talk about fur mutating into down feathers and not sound totally stupid. But flight feathers are so totally different from down feathers that you'd need TWO mutations to get to them i.e. one mutation to get from fur to down feathers and then another to get from down feathers to flight feathers.


http://www.birds.cornell.edu/AllAboutBirds/studyingbirdsi/feather_detail.gif

Flight feathers are asymmetric (one side shorter than other) and they pivot so as to open and let air pass through on upstrokes and close again on down-strokes and a the short side is the locking side. Flight feathers involve a complex system of barbules and hooks  to create the strength needed to bear weight. Down feathers don't have any of that stuff.

The question is, what kind of a mutation would cause down feathers to mutate into flight feathers ONLY ON THE CREATURE'S ARMS where they will be needed after other mutations turn those arms into wings??


What Is the Evidence for Feathers Before Flight?

Feathers are branched structures consisting of β-keratin—a rigid protein material formed by pleated β sheets—with a hollow central shaft. They are strikingly different from other forms of vertebrate integument such as scales, skin, and hair. Until recently, evolutionary hypotheses envisioned their origin through elongation of broad, flat scales driven by selection for aerial locomotion such as gliding or flapping flight. Over the course of the past two decades, fossil discoveries, especially from northeast China, have revealed that the early precursors of feathers were filament-like rather than expanded scales and that branched pinnate feathers of modern aspect predate the origin of active flight.

The Chinese deposits provide one such unique snapshot, where over a thousand specimens with fine details of soft tissues such as feathers, hair, and skin are preserved in ash-rich lake deposits ranging from the Late Jurassic (∼150 million years ago) to the Early Cretaceous (∼120 million years ago). Fossils from these deposits have revealed that dinosaurs that were inferred from bone characteristics to be closely related to living birds also share more features of feather structure.


Oh, wow, this article is so classic of the evolutionary genre, it’s a virtual gift to creationists.  Aside from the obvious evidential conclusion that dinosaur-to-bird evolution is a myth, Clarke used all the evolutionary tricks of the trade we’ve been pointing out in the Darwin lit for 12 years now: the Stuff Happens law, just-so stories, shielding complex changes in words like “novelty” and “innovation,” promissory notes, the coulda-woulda-shoulda habit, embedding evolution in terms like “protofeathers,” the convergence concoction, using passive verbs and subjunctive mood as covers for ignorance, composite explanations, punk eek, incredible stasis, ghost lineages, “more research is needed,” job security for storytellers, glossing over soft tissue in supposedly ancient material, tidbits of Lamarck and Haeckel as needed when gradualism doesn’t work, forcing uncooperative data into prefab scenarios, parading naked Emperor Charlie in public, sacrificing brains at his shrine – everything.  Hardly a sentence of this article is devoid of fallacies masquerading as science.

We hope you caught these things before the commentary began.  If not, you need Creation-Evolution Headlines as a deprogramming course.  Bookmark this site and come for your daily therapy.  Since Ken Dial made an off-camera appearance, we like all beginners to get the shock treatment in our commentary from 12/22/03 – the first time (now a decade ago, still cited favorably by Darwinists) the Montana drunkard-on-Darwine presented living partridge family chicks as possible props to an evolutionary tale.  Read that color commentary now; know the tricks, and you won’t be fooled again.


The Evolution of Feathers: A Major Problem for Darwinism

http://www.answersingenesis.org/articles/tj/v17/n1/feathers

Even though fossil impressions of feathers are abundant in the fossil record, and much has been written speculating on how scale-to-feather evolution could have occurred, not a shred of fossil or other evidence has ever been found to support the scale-to-feather evolution theory.1,23 In the words of Prum, understanding ‘the evolutionary origin of feathers has been constrained by the lack of any known ancestral feather morphologies or structural antecedents’.41

The evidence supports Klotz’s early conclusion that the ‘origin of feathers is still a real problem’ for Darwinism, and all contemporary theories of feather origin are hypothetical ideas that ‘can only be characterized as judicious speculation’.75 In short, nothing has changed since Regal stated ‘although most textbooks include some sort of speculation on the evolutionary origin of feathers … [a] morass of contradictory theories and muddy thinking … occurs in … much of the literature on this subject’.31

Although much speculation and major disagreements exist on how feathers ‘could have’ evolved, all existing theories are ‘just-so stories’, unsupported by fossil or historical evidence. The profound evolutionary enigma of feathers noted by Darwin76 and Heilmann77 remains, even today. The lack of evidence for feather evolution is not only a major problem for Darwinism, but the design and function of feathers provides evidence for both intelligent design and irreducible complexity. Flight and feathers are indeed a ‘miracle’.78 Feather evolution is related to the question of bird evolution.

Periodically, new bird fossils are found, but most of them have been of little or no use as evidence of bird evolution, and the few claimed examples typically generate much debate. For instance, Feduccia concluded that one recent find, known as Apsaravis, contributes little

   ‘… to our understanding of avian evolution, and its lack of a clear relationship with any kind of modern bird makes its significance ambiguous. If Apsaravis is not related to any modern ornithurine, how can it tell us anything important about the evolutionary questions raised by [its discoverers] Norell and Clarke?’79

The latest discovery of feathers on the birdlike, turkey-sized ‘theropods’ Caudipteryx and Protarchaeopteryx indicate that they are flightless birds. Much debate exists about this and related finds.80 Some consider these animals to be birdlike dinosaurs, or other dinosaur-like, flightless birds that have lost their full flight plumage (or never developed it). Conclusions on these finds will require much more study, and yet already have produced much debate and controversy.

Much disagreement still exists about Archaeopteryx, a discovery now around 150 years old. Likewise, the place in evolution, if any, of the recent finds may never be settled. Many of these finds are from a province of China, and already one find from this area has proven to be a hoax. Consequently, much more study is necessary to determine the value of these finds. So far, none of these finds challenges the conclusions presented in this paper, and early study of these finds has strongly supported the findings reviewed here.

In conclusion, we agree with Brush: ‘Uncountable numbers of words have been written in attempts to … reconstruct the primitive feather and explain why feathers evolved’.56 So far, all of these attempts have not only failed, but also have led to the conclusion that how feathers ‘arose initially, presumably from reptilian scales, defies analysis’.81


http://www.evolutionnews.org/2011/01/peer-reviewed_pro-intelligent042261.html

http://journals.witpress.com/pdfs/abstracts/D&NE040201a.pdf

http://blogs.christianpost.com/science-and-faith/pro-id-paper-examines-irreducible-complexity-of-birds-in-flight-9738/

http://creation.com/the-evolution-of-feathers-a-major-problem-for-darwinism

http://www.creationists.org/refuting-evolution-book-chapter-4.html

“THE IMPLICATION, THE RESEARCHERS SAID, IS THAT BIRDS ALMOST CERTAINLY DID NOT DESCEND FROM THEROPOD DINOSAURS, SUCH AS TYRANNOSAURUS OR ALLOSAURUS. THE FINDINGS ADD TO A GROWING BODY OF EVIDENCE IN THE PAST TWO DECADES THAT CHALLENGE SOME OF THE MOST WIDELY-HELD BELIEFS ABOUT ANIMAL EVOLUTION.
‘FOR ONE THING, BIRDS ARE FOUND EARLIER IN THE FOSSIL RECORD THAN THE DINOSAURS THEY ARE SUPPOSED TO HAVE DESCENDED FROM,’ RUBEN SAID.”

Mutation predicts 40 million years of fly wing evolution

This is remarkable when a paper in Nature magazine openly throws the towel and admits :

No evidence for the evolution of birds, feathers, and flight Cfz_da10

Our finding of striking similarities among mutational, genetic and
among-species variation coupled with a low rate of evolution are not readily explained by any of the available models of evolution. This is an important challenge for evolutionary theorists.

What is remarkable as well, is the misleading title of the paper....
http://www.nature.com.sci-hub.bz/nature/journal/vaop/ncurrent/full/nature23473.html?foxtrotcallback=true

The Genius of Birds
http://flightthegeniusofbirds.com/

Flight: The Genius of Birds - Official Trailer
https://www.youtube.com/watch?v=46rE4BfWN_M


Here's the bottom line we look at the anatomy of a bird its behavior its metabolism the structure of its feathers the structure of its muscles and so forth these are multiple independent points in a complex space out of which flight emerges and I think from a biological standpoint to fly at all requires a cause that's able to visualize a distant functional end point and bring together everything necessary to achieve that end point uniquely and universally in our experience only intelligence is capable of that kind of causal process an engineered system is the product of a mind that anticipated a problem and figured out a multi-step way of addressing that problem in birds you see exactly that kind of process they're engineering marvels they're works of art we know we're engineered things come from we know we're works of art come from so why would we attribute a bird to anything other than intelligence or mind



Last edited by Otangelo on Sun 31 Oct 2021 - 10:17; edited 20 times in total

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Otangelo


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http://icb.oxfordjournals.org/content/40/4/478.full

Explanatory History of the Origin of Feathers

However, because of the lack of knowledge about the roles and ecological relationships of protofeathers and of the most primitive feathers, it is not possible to test strongly either of these theories, or others as proposed in this symposium, against objective empirical observations to determine which is falsified or is the most probable.

Historical-narrative evolutionary explanations for the origin and further evolution of avian feathers involve two steps. The first phase reconstructs a series of probable morphological changes from a reptilian scale to the primitive feather. The second deduces possible functions and biological roles of the features and feasible selective demands on these features at all stages in its evolution. The best explanation for the evolutionary origin of feathers would be one consistent with historical-narrative evolutionary explanations for the origin and further evolution of other features in the history of birds. Feathers of Recent birds have a number of functions and biological roles, and it is difficult to ascertain which of these functions and roles were involved in feather origin. Two major rival published theories are based on the roles of feathers in insulating the body against heat loss and in providing an aerodynamic surface for flight. However, because of the lack of knowledge about the roles and ecological relationships of protofeathers and of the most primitive feathers, it is not possible to test strongly either of these theories, or others as proposed in this symposium, against objective empirical observations to determine which is falsified or is the most probable. Finally it is argued that test of historical-narrative evolutionary explanations, including classifications and phylogenies, is generally difficult to impossible because of the lack of the necessary objective empirical observations.



Last edited by Admin on Thu 13 Nov 2014 - 1:10; edited 1 time in total

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Otangelo


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http://reasonandscience.heavenforum.org/t1694-evolution-of-birds-feathers-and-flight

In order for an organism to fly, its entire body would have to evolve to a state where it's light enough for wings to support it. You need wings that are light enough yet strong enough to support the body. You need muscles powerful enough to flap those appendages quickly enough (70 beats per second in the case of a hummingbird!) for a sustained period of time. The development must be symetrical, because having just one wing does no good. If wings evolved from legs, how well could an animal evade predators during the in-between stages where the legs are too long and flimsy to walk on, but not yet light enough to enable flight? Natural selection will take its toll on anything that even comes close. All this assumes the wing has evolved into the shape of a workable airfoil that actually flies in the first place! The list goes on and on and on. I'm sorry, but the evolutionist's magic wand of millions of years is still far too short for anything as complex as flight to develop as a result of purely random changes to DNA. The ability for animals to fly is one of the reasons I find evolution absolutely implausible as an explanation of how life developed.



Last edited by Admin on Sun 6 Jul 2014 - 17:26; edited 1 time in total

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http://espanol.apologeticspress.org/articles/2534

The evolution of insect wings and subsequent flight is a concept impossible for evolutionists to explain. Insects are the ultimate flying machines—even humans’ most state-of-the-art aircraft cannot match the flight of insects. There is no way that the insects could have gradually evolved flight, nor is there fossil evidence of any intermediate species of insect between flying and non-flying insects. The fossil record indicates that if, in fact, flight evolved in insects, then it did so very rapidly. However, such a rapid, complex evolutionary advancement is impossible, and even goes against evolutionary theory. All of the evidence exemplifies elaborate design, and documents that everything was created fully functional in the beginning. All evidence points toward the intelligent design of insect flight—its form, function, and creation.

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http://creationsensation.blogspot.com.br/search/label/dinosaur%20bird%20evolution


1. There is no observational evidence to support the claim dinosaurs evolved into birds.
2. Evolutionists commonly resort to artistic drawings in textbooks rather than real evidence.
3. Evolutionists have produced a history of false claims.
4. The scientific evidence supports dinosaurs and birds lived at the same time just as the Bible teaches.




Origin of Avian Flight

http://www.evolutionnews.org/2013/10/the_origin_of_a077291.html

As a rule, a scientific explanation should avoid several common fallacies. One is the post-hoc fallacy: claiming that A caused B simply because A preceded B. Another fallacy is ad hoc reasoning: multiplying auxiliary hypotheses to maintain one's favored hypothesis. A third fallacy is begging the question. For instance, if an ID proponent were to state in a debate with an evolutionist about the origin of flight, "Because birds are designed, its flight systems must also have been designed," that would beg the question at issue. An even worse error is to ignore or arbitrarily "rule out of bounds" alternative explanations.

Some of the recent Darwinian accounts for the origin of flight commit all these fallacies. For instance, a news item from the University of Southampton is titled, "Dinosaur wind tunnel test provides new insight into the evolution of bird flight." This completely ignores all non-evolutionary explanations from the outset. All claims thereafter are doomed to beg the question of evolution.

In the article itself, we see the other fallacies fly by: one of the professors who put a model of the four-winged dinosaur Microraptor gui into a wind tunnel to test its aerodynamics committed several of the fallacies in these statements:

"Significant to the evolution of flight, we show that Microraptor did not require a sophisticated, 'modern' wing morphology to undertake effective glides, as the high-lift coefficient regime is less dependent upon detail of wing morphology."

"This is consistent with the fossil record, and also with the hypothesis that symmetric 'flight' feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form aerodynamically capable surfaces." (Emphasis added.)

But the issue at hand is the origin of powered flight, not just gliding. As shown so beautifully in the Flight film,

true powered flight by any heavier-than-air vehicle (whether avian or artificial) requires a complex suite of interacting systems.

The professor begs the question that gliding will evolve into powered flight. He commits the post-hoc fallacy by assuming that feathers "first evolved... for non-aerodynamic functions" then were later adapted for flight. And he commits ad hoc reasoning by invoking some unknown function for feathers in dinosaurs. (See also his team's paper in Nature Communications.)

What about those feathers on dinosaurs? Various "integumentary structures" have been found associated with fossils of some dinosaurs, but assuming they "evolved" into true flight feathers would commit the post-hoc fallacy again, besides begging the question that evolution "adapted" them for flight later.

Microraptor itself, with abundant feathers of modern aspect on four wings, is dated later than Archaeopteryx, a powered flyer. One fossil M. gui specimen was even found with a bird in its stomach, PNAS reported. Without getting into the weeds about fossils of feathers, since we want to compare explanations for the origin of powered flight, suffice it to say the record is confusing, even to Darwinian evolutionists, as Julia Clarke wrote in Science a few months ago:

Evidence is thus accruing for the function of early pinnate feathers in sexual selection, but there is little consensus on shifts in feather function associated with the evolution of flight. Reconstruction of ancestral conditions for the bird lineage requires consensus on the evolutionary relationships of key species. These species differ in feather shape as well as in their organization and layering on the forelimb and hind limb. Whether observed differences can presently speak to a gliding or flapping origin for flight is debated.

No wonder the film said that evolutionary theories about the origin of flight are highly controversial.

In its coverage of the Microraptor wind-tunnel experiment, New Scientist showed its propensity for ad-hoc reasoning: "plumage might not have evolved for flight but may instead have been a key aspect of sexual-selection displays."
More question-begging, alternative-ignoring, ad-hoc reasoning can be seen in a news item from the University of Oxford about bird tails. The article claims that shortened tails "gave early birds a leg up" in evolution -- "as soon as this happened it freed up their legs to evolve to become highly versatile and adaptable tools that opened up new ecological niches." Since this occurred after "birds had already evolved powered flight," though, it's irrelevant to the question of the origin of powered flight. It just shows the propensity by some evolutionists to beg questions and ignore alternatives.

Perhaps the most bizarre recent case of question-begging, ad-hoc reasoning is an item from McGill University with a Kipling-style just-so story title, "How birds got their wings." It basically claims that if you allow birds to evolve flight, they will:

This limb scaling changed, however, at the origin of birds, when both the forelimbs and hind limbs underwent a dramatic decoupling from body size. This change may have been critical in allowing early birds to evolve flight, and then to exploit the forest canopy, the authors conclude....

As forelimbs lengthened, they became long enough to serve as an airfoil, allowing for the evolution of powered flight....

Our findings suggest that the limb lengths of birds had to be dissociated from general body size before they could radiate so successfully. It may be that this fact is what allowed them to become more than just another lineage of maniraptorans and led them to expand to the wide range of limb shapes and sizes present in today's birds.

Needless to say, this explanation is unsatisfying. If changing limb ratios is all it takes to "allow" animals to fly, why didn't pigs try that? What "allowed" the simultaneous changes to the avian lung, flight feathers, and navigation? Why did the bones become hollow? How were the digestive, muscular, and respiratory systems overhauled, and how did they have any fitness value before powered flight emerged?

The ID Alternative

In Flight, Paul Nelson seeks the "vera causa" (true cause) of avian flight.

Now in the case of the origin of flight, we have a complex function, with all the associated anatomy and behavior and so forth, and the question we really should be asking is, what is the cause that is sufficient to bring this about? What is the vera causa of avian flight?

Nelson, Tim Standish and Ann Gauger consider the alternative of evolution or any other explanation that requires naturalism, resulting in just the "appearance of design" without actual design. Then they review all the systems that make flight possible, from feathers to "the most efficient respiratory system in the animal kingdom." Standish says:

Obviously, you're coordinating many, many, many different systems that have to be all exactly right for the bird to fly. And the more systems and component parts that are involved, the more challenging it is to explain how all of them came together so precisely in a bird.

Here's how Nelson sums up the ID explanation:

Here's the bottom line. You look at the anatomy of a bird, its behavior, its metabolism, the structure of its feathers, the structure of its muscles and so forth -- these are multiple independent points in a complex space, out of which flight emerges. And I think from a biological standpoint, to fly at all requires a cause that is able to visualize a distant functional endpoint, and bring together necessary to achieve that endpoint. Uniquely, and universally in our experience, only intelligence is capable of that kind of causal process.

Standish adds:

An engineered system is the product of a mind that anticipated a problem and figured out a multi-step way of addressing that problem. In birds you see exactly that kind of process. I believe intelligent design is the best explanation for avian flight, because it's the best explanation for every other kind of flight that we see. So why would I suddenly change the rules when I go from a 747 to a pigeon? ... They're engineering marvels. They're works of art. We know where engineered things come from. We know where works of art come from. So why would we attribute a bird to anything other than intelligence or mind?

The ID explanation, therefore, rests on known causes from our uniform experience. An explanation that avoids ad-hoc reasoning, the post-hoc fallacy, and question-begging arguments -- one that explores rather than ignores alternatives -- one that seeks the vera causa from known causes sufficient to bring about a phenomenon -- that explanation should be the one judged scientifically the best.

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http://espanol.apologeticspress.org/articles/2534

Insects require a highly specialized flight apparatus. Biomechanical prerequisites for insect flight include extremely powerful muscles in the thorax to generate force, axillary apparatus (the “shoulders” of the insects) to transfer force, and the wings themselves to convert force into flight. Most insects can perform a variety of aerial feats, because they possess a direct as well as an indirect muscular system. Direct muscles are attached directly to the wings, indirect muscles are not. The dorsoventral (midline on the back—MV) muscles contract to raise the wings. The longitudinal muscles contract to lower the wings. When the dorsoventral muscles contract, the tergum (back segments—MV) is lowered and the wings rotate about the other hinges and rise. When the longitudinal muscles contract, tergum is forced up again and the wings rotate in the opposite sense about the outer hinges. Additionally, insects are able to flap their wings in figure-eight patterns because of their dorsoventral muscles that are attached to the wing base.

As a result of their unique musculature, insects can beat their wings much faster than birds, which possess a direct muscular system. Humans also possess a direct muscular system. Break from your reading for a moment and try something. Extend your arms out to your sides parallel with your shoulders. Now flap your arms as fast as you can for five seconds. I would be impressed if you could flap twenty times. Insects can beat their wings up to 1,000 times in one second. This feat is a result of their unique muscular system as well as the unique design of the insect’s brain. The muscles themselves require few orders from the brain. When a human flaps his arms, his brain has to command each stroke on each side of his body. The insect’s brain does not have to think about every wing beat; it only needs to instruct the wings to begin or stop flapping.

When you flapped your arms, you probably not only looked silly to those around you, but you probably also became tired very quickly. Now imagine flapping your arms 200 times as fast! This would cause even the strongest of humans to collapse from exhaustion. The metabolic rate of all flying creatures is extremely high in relation to land-dwelling creatures. Dudley even found himself confessing: “Flight is energetically very costly, and the metabolism of winged insects represents an extreme of physiological design among all animals” (Dudley, 2000, emp. added). Insects do not have a central breathing organ (like lungs); instead, oxygen is supplied to the flight muscles via the insect’s tracheal respiratory system. Insects do not breathe as humans do. They do not pull air in, but simply diffuse gases that pass through the tracheal respiratory system. This system comprises up to 10 percent of the insect’s body mass. The whole body is equipped for flying, yet many scientists purport that it is an evolutionary accident that they are able to fly.

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Feathers Not Flying Over New Dinosaur Fossil


There are three general problems with claims of feathered dinosaur fossils: (1) they aren't feathered (i.e., they have dinofuzz, a wispy hair-like feature that isn't the same as feathers), or (2) they aren't dinosaurs (i.e., they are secondarily flightless birds and not dinosaurs at all), or (3) they aren't fossils (i.e., they're one of the examples of fake fossils that's appeared like the infamous Archaeoraptor). A new fossil ornithischian dinosaur reported inScience is said to have had "avianlike feathers," but some critics think it belongs in category (1) -- i.e., it wasn't feathered at all. The paper on the fossil inScience states:

Here we report a new ornithischian dinosaur, Kulindadromeus zabaikalicus, with diverse epidermal appendages, including grouped filaments that we interpret as avianlike feathers.

Yet according to an article in National Geographic, "Fluffy Dinosaur Raises Questions About the Origin of Dinofuzz," we can't establish that these are feathers:

In terms of typical dinosaur tubercles, Kulindadromeus had hexagonal scales on its lower legs, rounded scales around the hand and ankle, and rows of large scales along the tail. But the fossils also preserved a trio of feathery structures. Single filaments surrounded the dinosaur's head, torso, and back, while the dinosaur's upper arms and legs were covered in multi-filament plumes and the dinosaur's lower leg sported "ribbon-shaped elements" that have not been seen in any other species so far.

The question is whether these fluffy structures are true feathers or fluffy imitations. This has major implications for when true feathers and their immediate forerunners evolved in dinosaurs. If the dinofuzz on Kulindadromeus really is equivalent to that borne by theropods like Sinosauropteryx, then the beginnings of feathers probably coincided with the origin of dinosaurs. If the structures are superficially the same, but not truly equivalent, then feather-like structures either evolved more than once or diverged from some earlier, as-yet-unseen type of integument.
For the moment, there's still no way to distinguish between these alternative scenarios. At a basic anatomical level paleontologists have yet to discern whether the structures on Psittacosaurus ,Tianyulong , and Kulindadromeus can truly be called feathers. Not to mention the need for better fossils of older dinosaurs, close to where the major lineages split, to follow feather origins, as well as a more refined understanding of the circumstances under which fluff, fuzz, and bristles are likely to be preserved.

Did you note the statement in the last paragraph? "At a basic anatomical level paleontologists have yet to discern whether the structures on Psittacosaurus ,Tianyulong , and Kulindadromeus can truly be called feathers." Looking at the diagram from the paper, they sure don't look much like feathers:

I see wispy hair-like structures. I see dinofuzz. But I don't see feathers. A prominent critic writing in National Geographic says much the same. Yet these structures are being unapologetically called "feathers" in Science. It seems to me the theory is getting ahead of the data.

http://www.evolutionnews.org/2014/08/feathers_not_fl088501.html

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Functional roles of Aves class-specific cis-regulatory elements on macroevolution of bird-specific features

http://www.nature.com/articles/ncomms14229?WT.feed_name=subjects_evolutionary-developmental-biology

Unlike microevolutionary processes, little is known about the genetic basis of macroevolutionary processes. One of these magnificent examples is the transition from non-avian dinosaurs to birds that has created numerous evolutionary innovations such as self-powered flight and its associated wings with flight feathers. By analysing 48 bird genomes, we identified millions of avian-specific highly conserved elements (ASHCEs) that predominantly (>99%) reside in non-coding regions. Many ASHCEs show differential histone modifications that may participate in regulation of limb development. Comparative embryonic gene expression analyses across tetrapod species suggest ASHCE-associated genes have unique roles in developing avian limbs. In particular, we demonstrate how the ASHCE driven avian-specific expression of gene Sim1 driven by ASHCE may be associated with the evolution and development of flight feathers. Together, these findings demonstrate regulatory roles of ASHCEs in the creation of avian-specific traits, and further highlight the importance of cis-regulatory rewiring during macroevolutionary changes.

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Axis Specification and the Avian “Organizer”

As a consequence of the sequence in which the head endomesoderm and notochord are established, gastrulating avian (and mammalian) embryos exhibit a distinct anteriorto- posterior gradient. While cells of the posterior portions of the embryo are still part of a primitive streak and entering inside the embryo, cells at the anterior end are already starting to form organs. For the next several days, the anterior end of the embryo is more advanced in its development (having had a “head start,” if you will) than the posterior end. Although the formation of the chick body axes is accomplished during gastrulation, axis specification begins earlier, during the cleavage stage


The role of gravity and the posterior marginal zone PMZ 
The conversion of the radially symmetrical blastoderm into a bilaterally symmetrical structure appears to be determined by gravity. As the ovum passes through the hen’s reproductive tract, it is rotated for about 20 hours in the shell gland. This spinning, at a rate of 15 revolutions per hour, shifts the yolk such that its lighter components (probably containing stored maternal determinants for development) lie beneath one side of the blastoderm. This imbalance tips up one end of the blastoderm, and that end becomes the posterior marginal zone, where primitive streak formation begins 

No evidence for the evolution of birds, feathers, and flight QGrrLKj
Specification of the chick anterior-posterior axis by gravity.
(A) Rotation in the shell gland results in (B) the lighter components of the yolk pushing up one side of the blastoderm. (C) This more elevated region becomes the posterior of the embryo.

It is not known what interactions cause this specific portion of the blastoderm to become the PMZ. Early on, the ability to initiate a primitive streak is found throughout the marginal zone; if the blastoderm is separated into parts, each with its own marginal zone, each part will form its own primitive streak. However, once the PMZ has formed, it controls the other regions of the margin. Not only do the cells of the PMZ initiate gastrulation, they also prevent
other regions of the margin from forming their own primitive streaks. It now seems apparent that the PMZ contains cells that act as the equivalent of the amphibian Nieuwkoop center. When placed in the anterior region of the marginal zone, a graft of PMZ tissue (posterior to and including Koller’s sickle) is able to induce a primitive streak and Hensen’s node without contributing cells to either structure. Current evidence suggests that the entire marginal zone produces Wnt8c (capable of inducing the accumulation of β-catenin) and that, like the amphibian Nieuwkoop center, the PMZ cells secrete Vg1, a member of the TGF-β family.

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Muscle function in avian flight: achieving power and control: By evolution, or design ?

Flapping flight places strenuous requirements on the physiological performance of an animal. Bird flight muscles, particularly at smaller body sizes, generally contract at high frequencies and do substantial work in order to produce the aerodynamic power needed to support the animal's weight in the air and to overcome drag. 3

Bird flight requires muscles so massive that they can account for a third or more of a bird’s body weight. 2

The Supracoracoideus – An Ingenious Adaptation For Flight
There is a unique muscle arrangement that allows the return stroke of the wing while maintaining aerodynamic stability. 1 But one of the dilemmas of bird flight is how to design a muscle arrangement that will power the upstroke of the wing and still maintain that low center of gravity.  Muscles can only contract under power so it seems logical that the muscle that would provide the upstroke would be along the back.  But such an arrangement would place a relatively large muscle mass high on the body, raise the center of gravity and compromise aerodynamic stability.  Anyone who has ever eaten a chicken back knows that there is very little meat (muscle) there and that particular placement of the muscle along the back is not the solution that nature came up with.

The solution is truly ingenious. The muscle, known as the supracoracoideus, connects to the top of the humerus by way of a pulley, an ingenious mechanism found nowhere else among vertebrates. Birds are amazingly designed for flight. Among the most dramatic are the extreme enlargement of the breast muscles and the skeletal design that accommodates them, and a unique pulley system that allows a muscle located under the wing to raise it. All of this points again to the amazing structure and function of birds.

In the graphic you can see how the contraction of the pectoralis would power the wing down.  But beneath and lying next to the pectoralis is another muscle – the supracoracoideus (the word means “above the coracoid” bone).  The supracoracoideus is antagonistic to the pectoralis and provides the upstroke.  It is attached to the upper side of the humerus by a unique “rope and pulley” arrangement of a tendon that travels up and over a notch in the scapula before attaching to the humerus.  So even though the muscle is below the humerus, the direction of pull is from slightly above so that when it contracts it raises the wings and aerodynamic stability is maintained.

Since both muscles are required, that raises the question: What evolved first : The supracoracoideus muscle or pectoralis muscle ?

The avian pectoralis is well suited to performing work with large length excursions. This is a prerequisite for powering flight because the wings must move through a large excursion during downstroke to produce effective aerodynamic lift.

If large lengths of excursion is a prerequisite for flight, that of course raises the question how the muscle could be the product of evolution.

Story on Evolution of Birds Glosses Over Details 4
The beautiful Illustra documentary Flight: The Genius of Birds gives an elegant and satisfying explanation for flight, because it doesn’t gloss over the details, but accounts for all the traits needed for powered flight: efficient one-way lungs, efficient digestive and excretory systems, the beautifully engineered flight muscles that provide a compact center of gravity, the hollow bones, the navigation systems, the sensory components (able not only to see details from the air but to sense the magnetic field), the exquisite design of feathers, and the behaviors that allow birds to take advantage of air currents, including the lift from other birds in formation flight.  The integrated systems that allow an eagle to pick a fish out of a lake, a hummingbird to hover in mid-air sucking its food out of a flower with a specialized nectar-trapping tongue, or a snowy egret with its large, elegant wings to fly between tree limbs without hitting them, are explained by appealing to what we know in our universal experience about complex functional systems.  Intelligent design is a known “vera causa” (true cause) that can account for the observations.
https://crev.info/2014/02/story-on-evolution-of-birds-glosses-over-details/


Never do we see blind, unguided processes leading to complex functional systems with integrated parts contributing to the overall design goal.  Intelligent design is, therefore, the best scientific explanation. 

With its high perhapsimaybecouldness index, its stretchable rates of evolution (a clear ad hoc theory rescue device), and its copious use of magic words (emerged, arose, developed, appeared), it reduces to “birds evolved because they evolved.”  If the public were allowed to hear the two explanations side by side, there would be no contest. Darwin’s flightless DODO birds would go running out of the auditorium in shame.



No evidence for the evolution of birds, feathers, and flight Suprac10







https://www.youtube.com/watch?v=aFdvkopOmw0

1. https://www.featheredphotography.com/blog/2013/11/14/the-supracoracoideus-an-ingenious-adaptation-for-flight/
2. https://www.birdwatchingdaily.com/news/science/the-amazing-muscles-and-bones-that-make-birds-fly/
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130450/
4. https://crev.info/2014/02/story-on-evolution-of-birds-glosses-over-details/

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The molecular evolution of feathers with direct evidence from fossils

1. https://www.pnas.org/content/116/8/3018

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Craig B. Lowe Feather Development Genes and Associated Regulatory Innovation Predate the Origin of Dinosauria 18 November 2014 1
On the branch leading to modern birds, we detect a strong signal of regulatory innovation near insulin-like growth factor binding protein (IGFBP) 2 and IGFBP5, which have roles in body size reduction, and may represent a genomic signature for the miniaturization of dinosaurian body size preceding the origin of flight.

Feathers constitute complex-branched structures that arise through interactions between the dermis and epidermis. Although feathers were long thought to be a key innovation associated with the origin of avian flight, paleontological discoveries over the past 15 years indicate a more ancient origin; filamentous feather precursors are now known to be present in many lineages of nonavian dinosaurs, and pennaceous feathers clearly arose prior to the origin of flight. At the same time, the molecular processes underlying feather development and deployment throughout the integument are becoming better known through studies of gene expression patterns  and natural mutants. Comparative genomics can offer insights into the evolutionary history of functional elements in the genome; however, aside from the β-keratins, which are known to have diversified extensively on the lineage leading to birds, we know little about evolutionarily novel genes or noncoding regions associated with feather development. Recent studies have shown that regulatory changes underlie many key phenotypes in vertebrates, but regulatory innovations associated with the origins of feathers have not been systematically explored. In particular, conserved nonexonic elements (CNEEs) have emerged as important regulators of gene expression and have revealed the evolutionary dynamics of genomic regions associated with novel phenotypes, such as mammalian hair.

CNEEs and Constraint in the Avian Genome
We identified a set of 193 genes that have been associated with feather development through mutant phenotypes or spatiotemporally restricted expression patterns. To investigate the evolutionary history of these genes and their potential regulatory elements, we constructed a 19-way whole-genome alignment referenced on the chicken genome containing four birds, two crocodilians, two turtles, a lizard, four mammals, a frog, and five actinopterygian (ray-finned) fish. Regions of the genome showing evolutionary constraint were identified using a phylogenetic hidden Markov model to detect regions of the alignment evolving more slowly than synonymous sites in coding regions. Overall, 957,409 conserved elements totaling approximately 71 Mb and spanning approximately 7.2% of the chicken genome were identified, a higher percentage than the 5% often reported for the human genome. This result is consistent with the small (1.2 Gb) size of the chicken genome relative to the human genome, making the total amount of sequence annotated as constrained about half of what is currently reported for human. To identify putative regulatory elements we removed any regions overlapping an exon annotated in chicken, or another species, resulting in 602,539 CNEEs covering 4.4% of the chicken genome. We identified the gene that each CNEE is likely to regulate by assigning each CNEE to the gene with the closest transcription start site, and found that 13,307 of the CNEEs were associated with the 193 feather-related genes in the data set. Although regulatory elements can act over long genomic distances that include genes not regulated by the elements, experimentally identified enhancers tend to be closest to genes with expression in the same tissues and at the same times in development. Additionally, many regulatory regions undergo rapid evolution and turnover, and these will be missed by our analysis. Due to their different functions, we split the list of 193 feather-related genes and their associated CNEEs into a structural set of 67 keratin genes and a patterning set of 126 nonkeratin genes and analyzed these groups separately.

An Ancient Genic Toolkit and Extended Regulatory Evolution Are Associated with Feather Origins
The genic and regulatory components of the keratin and nonkeratin sets show very different patterns across the 500-My backbone of our tree, on the lineage leading from the common ancestor of vertebrates to the chicken . The most ancient branch in our analysis, leading to the common ancestor of ray-finned fishes and other vertebrates, shows the strongest enrichment for the nonkeratin feather genes (1.7 times expected), with smaller numbers of nonkeratin feather genes arising on branches leading to tetrapods and less inclusive clades. No members of this nonkeratin feather gene set are reconstructed to have arisen after the ancestor of birds and turtles. Although ancient genes are more likely to be studied during chick development, the nonkeratin genes in our study were even more ancient than we would expect taking into account this bias. The inferred first appearance of nonkeratin protein-coding regions that are involved, for example, in placode patterning and feather ontogeny in birds is consistent with these genes being part of an ancient developmental toolkit (figs. 1 and 2).

No evidence for the evolution of birds, feathers, and flight Msu30910
Major genomic events underlying the origin of feathers.
The colored backbone of the tree shows three tracks: CNEEs, nonkeratin feather genes (n = 126), and keratin genes (n = 67). Rates of origination of these three genomic classes are indicated by the colors for each stem internode and track in the tree, with blue colors indicating low origination rates and red colors indicating high origination rates. Key events at the level of coding regions (genes) and regulatory elements are indicated. The colors of the silhouettes at right indicate the percent of the feather regulatory component present in the chicken genome inferred to have arisen in the ancestor of each indicated taxon. For example, the fish are inferred to possess about 28% of the CNEEs associated with feather genes in chicken, whereas 86% of the observed chicken CNEEs are inferred to have arisen by the ancestral archosaur, including nonavian dinosaurs.

My comment:  This is not science. It is just so storytelling without evidence. The transition claimed is just hypothesized and imagined, not demonstrated, empirically.

Body Size Genes Exhibit Exceptional Regulatory Innovation in Dinosauria
Genes with an anomalously large number of regulatory elements arising in birds after their divergence from extant crocodilians may contribute to the origin of avian phenotypes. A genome-wide survey of 1-Mb genomic windows revealed 23 segments of the chicken genome possessing anomalously high numbers of CNEEs arising on the branch leading to birds (fig. 3a)

No evidence for the evolution of birds, feathers, and flight Msu30911
Identification of regions of the avian genome with signatures of exceptional regulatory innovation on the archosaur lineage that includes birds and other dinosaurs.
(a) A genome-wide plot of the density of CNEEs arising on the archosaurian branch leading to the avian ancestor. Red regions indicate those areas enriched compared with the distribution of CNEEs on other branches (gray line in ) and green squares indicate the 23 significant peaks of enrichment for bird-specific CNEEs relative to a uniform distribution throughout the genome. We examined the closest upstream and closest downstream genes and for select peaks a flanking gene is indicated along with a proposed role in avian morphological evolution (key at top); regulatory innovation may also have played a role in earlier dinosaur-lineage evolutionary dynamics. 
(b) The densest region for bird-specific CNEEs in the chicken genome is in a gene desert on chromosome 7 with IGFBP2 being the closest well-annotated refseq gene and IGFBP5 being the closest gene prediction. CNEE density on all branches other than the one leading to birds is indicated in gray. 
(c) UCSC Genome Browser shot of a CNEE-rich region in the vicinity of IGFBP2 and IGFBP5, which functions in limb development and body size regulation (see main text, supplementary table S4, Supplementary Material online), showing CNEEs found only in birds (red boxes) or arising on deeper branches in the vertebrate tree (gray boxes). Regions of aligning sequence for representatives of the 19 included taxa are in green.

1. https://academic.oup.com/mbe/article/32/1/23/2925601

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Mao Kondo Flight feather development: its early specialization during embryogenesis 16 January 2018 1
Flight feathers, a type of feather that is unique to extant/extinct birds and some non-avian dinosaurs, are the most advanced type of feather. In general, feather types are formed in the second or later generation of feathers at the first and following molting, and the first molting begins at around two weeks post-hatching in chicken. However, it has been stated in some previous reports that the first molting from the natal down feathers to the flight feathers is much earlier than that for other feather types, suggesting that flight feather formation starts as an embryonic event. The aim of this study was to determine the inception of flight feather morphogenesis and to identify embryological processes specific to flight feathers in contrast to those of down feathers.

Co-optation of molecular cues for axial morphogenesis in limb skeletal development may be able to modify morphogenesis of the feather bud, giving rise to flight feather-specific morphogenesis of traits.

Feathers are specialized skin derivatives (integument appendages) that are unique to extant/extinct birds and some non-avian dinosaurs; in living birds, most of the body is covered with some kinds of feathers. Feathers in birds, which serve more than 20 different functions, including thermoregulation, physical protection, tactile sensation, various types of visual signaling such as display in courtship, and flight, are functionally refined integument appendages. Bird feathers can be classified into many types, such as down, bristle, and contour feathers (including flight feathers), and various feather types enable feathers to exert a variety of functions. The flight feather is the most advanced type of feather. The powerful flight of birds is made possible by flight feathers, which have asymmetric shapes of the vanes along the rachis ( Fig. 1) 

No evidence for the evolution of birds, feathers, and flight 40851_2017_85_Fig1_HTML
Fig.1 Development of remex-type flight feathers after hatching.
a A flight feather in the adult chicken. 
b Natal down feather in the abdominal tract at 1 dph. An uprooted abdominal natal down feather is shown on the right side. 
c Ventral view of the FFF region at 1 dph. Some rows of feathers in the ventral surface of the wing are trimmed. Staples indicate the FFF region. An magnified photograph is shown on the right side. 
d–f A feather uprooted from the FFF region at 1 dph (d), 5 dph (e), and 7 dph (f). Note that in e, a distal downy part is connected with a proximal bilateral part that starts opening (white arrow). Scale bars: 1 cm

that aero-mechanically enable birds to fly. 

Question: Is the origin of asymmetric shapes, not an all-or-nothing business? 

There are mainly two body regions where flight feathers grow; one region (for remiges) is the posterior margin of the wing (forelimb) and the other (for rectrices) is the lateral margin of the tail. A feather is an exterior structure on the skin in general, but the shaft (quill) of the remex-type flight feather is anchored to the bone (ulna and metacarpal/phalanges of digit) with extra muscles and neural networks for motor control. These bones have protrusions on the surface (quill knob) that directly attaches to the proximal end of the flight feather calamus (calamus; the short, tubular base of the quill), which functions as mechanics of flight.

During embryogenesis and molting, all feathers develop from primordial feather buds with follicles (feather follicles) at the base of it, and repetition of feather development enables cyclic molting. (Moulting is the periodic replacement of feathers by shedding old feathers while producing new ones). A chick after hatching appears to be covered with fluffy downy feathers (natal down feathers), and diversification of feather types emerges in the second or later feathers that form at the first and following molting. In the chicken, the first molting generally begins at around two weeks post hatching, and it is therefore possible that complex features of the flight feather would be provided at molting after hatching. However, it has been stated in some previous reports that the first molting from the natal down feather to the remex-type flight feathers is much earlier than that for other feather types (see also Fig. 1b-f). Moreover, the feather follicles for the remiges reach the wing bone by the time of hatching, although details remain obscure. In order to clarify the early origin of flight feathers, we speculated that flight feather development may start much earlier as an embryonic event in mid-development in chicken. If this is the case, it is possible that the mechanism for morphogenesis of advanced features of the flight feather has not simply added to the mechanism for the morphogenesis of the primitive types of feathers but is instead a modified/peculiar morphogenetic process.

Considering the functional peculiarities of the flight feather, when and how flight feathers develop are important issues for feather biology in general. The aim of this study was to determine the incipient morphogenesis of the flight feather, focusing on when morphological traits of the remex-type feather start developing and how special morphologies of remiges (e.g., attachment between the flight feather calamus and the bone) are established. There are already many descriptions of the morphology, morphogenesis and molecular characters of the flight feather. Using such information, we present here morphological, histological, and molecular marker observations of the flight feather bud, and describe its developmental sequence. Integrating such descriptive information will also serve as the basis of feather diversification. Our results suggest that flight feather morphogenesis in the chicken is an embryonic event starting from the middle of chick development and that the first down feathers in the flight feather-forming region, the follicles of which have already reached the bone, are special feathers that are different from other natal down feathers. 

Flight feather morphology and development after hatching
In all experiments described below, we used flight feathers in the zeugopod for specimens of flight feathers (Fig. 1a) and their primordia, and compared them with abdominal feathers (Fig. 1b). In this study, we defined the place where remex-type flight feathers (remiges) a are formed as the “flight feather-forming region (FFF region, see Fig. 1c)”, which is the posterior margin of the zeugopod b and autopod c  in the wing. In the FFF region, the first generation of feathers is down-type and the second generation is remex-type.  In contrast to the morphology of natal down feathers on the abdominal surface at one day post hatching (dph) (Fig. 1b), feathers in the FFF region are composed of two different parts: a distal part resembling down feathers and a proximal part of a shaft without barbs visible at 1 dph (Fig. 1c, d) as described by Hosker [8]. Developing barbs here seem to be still inside the sheath of this proximal part of the developing feather and are therefore not visible yet as described by Alibardi [18]. The root of the proximal part is deeply embedded in the wing. At 5 dph, the distal portion of the proximal part begins to open, and barbs with a bilateral shape along the rachis can be seen (Fig. 1e, showing that the down feather is still on the distal end of the opening bilateral barbs). The remex-type asymmetric barbs further open at 7 dph, and the distal down part has dropped from this specimen (Fig. 1f). A series of observations (Fig. 1) confirmed that the distal part at 1 dph is the first down feather that connects with the second remex-type feather, although the remiges have not been opened yet at that time (Fig. 1d), suggesting that the first molting starts at around the hatching stage. It seems that the remex-type feather has already started developing at embryonic stages before hatching.

a Flight feathers (Pennae volatus) are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges, singular remex, while those on the tail are called rectrices, singular rectrix
https://en.wikipedia.org/wiki/Flight_feather

b  A section of an animal's limb corresponding to the forearm
https://en.wiktionary.org/wiki/zeugopod

c The distal part of a limb; a hand or foot

1. https://link.springer.com/article/10.1186/s40851-017-0085-4



Last edited by Otangelo on Sat 23 Oct 2021 - 0:13; edited 2 times in total

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A.C. McINTOSH Evidence of design in bird feathers and avian respiration 2009 1

Many have taken the view that design is only an illusion in living systems [1], arguing that such ‘apparent design’ and accompanying complexity can be explained by the neo-Darwinian paradigm. However, such thinking fails to realize that functional systems, in order to operate as working machines, must have all the required parts in place in order to be effective. If one part is missing, then the whole system is useless. The inference of design is the most natural step when presented with evidence such as in this paper, that is evidence concerning avian feathers and respiration. The counterargument has often been made that functional complexity can appear from simpler systems that evolve over time. However, there has never been a recorded observation of this happening experimentally in the laboratory (where the precursor information or machinery is not already present in embryonic form). Though it is true that a design action is also not observed in the laboratory, nevertheless the inference to original design and intelligence is a perfectly valid alternative from direct analogy to designs within the man-made world. Even though specified functional complexity has not been experimentally observed to develop from simpler systems, this has not deterred the stridency with which such views are put forward by some of evolution’s proponents. In particular, the arguments seeking to align such thinking with the principles of thermodynamics lead to, at best, speculative ideas to explain how these fundamental structures and information emerge. The powerful fundamental arguments from thermodynamics actually favor the straightforward view that such organizational structures cannot appear without pre-existing functional complexity being there, to begin with. Therefore, the main intention in this paper is to draw attention to machinery which can readily be understood by most readers with some scientific background and to appreciate some of the features which defy an explanation by slow gradual changes, as required by neo-Darwinian evolution.

It needs to be stated clearly that origins science, though it clearly has philosophical implications, is nevertheless a genuine scientific debate. It is not the prerogative of science to make statements beyond the remit of the study of natural systems, since, by its very nature, science can only be the study of the material world. Consequently, to try and assert that natural systems can only ever have come about by a preexisting natural system without intelligence is an unproven assumption, and must immediately be recognized as such. To take only natural causes as one’s starting point seems innocuous enough, for some would say that does it not helpfully separate ‘religious’ questions from ‘scientific’ ones? Surely ‘here is the way forward’ say a large group of scientists, most of whom have no predisposition to be either for or against any particular philosophical view of reality. They just wish to pursue science. However, what is a useful and pragmatic way forward, for taxonomic purposes, of describing rich, living biological systems, becomes totally inappropriate when looking at the origins of such systems, since to deny the possibility of the involvement of external intelligence is effectively an assumption in the religious category. Science can study the effect on the natural world of systems of pre-existing material, but it cannot preclude the possibility of intelligence extraneous to that very matter and energy being involved in its formation. To say otherwise is effectively wedding science to a narrow philosophical foundation. We quote here the important statement of a great thinker and evolutionist – Stephen Jay Gould, who often spoke against the position that there is necessarily an intelligence behind the design observed in nature:

Moreover, ‘fact’ does not mean ‘absolute certainty.’ The final proof of logic and mathematics flow deductively from stated premises and achieve certainty because they are not about the empirical world. ... In science, ‘fact’ can only mean ‘confirmed to such a degree that it would be perverse to withhold provisional assent. I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.

Gould is right that logic and mathematics flow from stated premises, and it is that very point that we seek to emphasise here. Once one opens the possibility that intelligence is involved, the evidence leads very naturally to the conclusion of design, not by going against the known empirical laws (such as gravity in the analogy of Gould), but precisely the reverse. We must keep to the ‘nullius in verba’ motto of the Royal Society (‘on the words of no one’), and not preclude from the outset where the evidence may lead.

Types of feathers 
Feathers are of different types depending on location. The major types of feathers are illustrated in Fig. 1, which shows that there are at least five different types. 

No evidence for the evolution of birds, feathers, and flight Types_10

Flight feathers are mainly the primary feathers on the outer part of the wing. These and the tail feathers are together called remiges. The primary feathers are larger in size relative to the other feathers, and asymmetric in shape. As the name implies, they bear the greatest aerodynamic load, and without them, a bird will not be able to fly. These are often the feathers cut in order to train a bird. They will, of course, regrow, but a bird is helpless without them. The secondary feathers are needed to complete the inner part of the wing and maintain stability. Those closest to the body of the bird are called the tertiary feathers. The base of the flight feathers are also covered by smaller feathers called covert feathers. These also thicken the leading edge of the wing such that an aerofoil shape is maintained in cross section by the extended wing. All the above are called pennaceous feathers as they have closely connected barbs and form aerodynamic surfaces. There are other feathers which are called plumulaceous, or downy, feathers. These have only a rudimentary rachis and a jumbled tuft of barbs with long barbules to provide an excellent thermal insulation. The details of a feather are shown in Fig. 2. Not shown in Fig. 1 are the tail feathers (retrices) which have a symmetrical shape but are designed for use as air brakes and also control the direction of flight.

One of the most easily overlooked feathers are those forming the alula (or alular) grouping – essentially a set of finger feathers on the leading edge of each wing of a bird. These feathers are crucial because, for low speed flight, they act as a leading edge slat and keep the boundary layer attached across the upper surface of the wing that is formed from the main primary, secondary and tertiary pennaceous feathers. The alula group of feathers are attached to a projecting digit coming from the humerus bone. This digit is called the pollex and acts rather like the human thumb. The number of alula feathers attached to the pollex depends on the species. The humming bird has two, the cuckoo has five or six, and there can be as many as seven. Without these small feathers, the control of flight would be extremely difficult at low speed.

Hook and ridge barbule arrangement of feathers Feathers are made of keratin, a protein also used to make hair and fingernails. There are differences in the exact type of keratin used. Feather keratin occurs in a ‘β-sheet’ configuration, which differs from the α-helices that generally occur in mammalian keratins. The β keratin of bird feathers is rather like a stretched spring in consistency. The fact that scales of reptiles are also made of keratin is used by some to propose that dinosaurs are the precursors to birds. However, it should be noted that there are significant hurdles to transform one type of keratin to the other. The feather grows from a follicle, and from the central rachis come barbs which give the vane of the feather. The details of the sophistication involved in the barb system of the pennaceous feather become clear under a microscope. In Fig. 3, barbules can be seen coming from each barb. They are only visible at the micro level, but have a structure that is essential for feathers to work as aerodynamic surfaces. The barbules in one direction are ridge-like, while the barbules in the opposing direction have hooks. Consequently, the hooks of the barbule in one direction grip the ridge of the opposing barbule. Figure 4 shows further details of this remarkable arrangement.

No evidence for the evolution of birds, feathers, and flight Types_11
Keratin sheath of feathers 
Feathers grow from follicles and are made from multilayered keratinocyte sheets. As already noted, the feather keratin is in a β-sheet configuration and develops within the follicle which supports, in the initial stages of growth, a cone arrangement made from a rachidial ridge (which becomes the rachis in the fully developed feather) and the barbs curled round with a longer circumference at the base of the cone and shorter barbs forming the tip. All this is enclosed in a keratin sheath, the lining of which is connected to the follicle as a single layer. As the plumage appears, at each feather follicle, the cone becomes a sheath and then gives way to the feather as it emerges from the vertex. These sheaths become tube-like and are present for any new feather. This will be the case for adults, as feathers are replaced in moulting, but are more visible and noticeable in a fledgling (see Fig. 5) since all the feathers are then developing together and emerge from the vertex of their coned follicles into individual separate tubes of keratin. 

No evidence for the evolution of birds, feathers, and flight Types_12

These tubes run the length of each feather, thus protecting the delicate feather barbs as they develop in the  embryo within the egg. The final emergence of the feathers in a fledgling can take a few weeks for these to unfold and the keratin sheath to break away – see Fig. 5.

Design features of feathers 
There is multifunctioning and multioptimisation in feather construction. There are the features which are immediately apparent such as aerodynamic loading and the material construction of rachis and barbs to sustain this. However, there are also more subtle features such as the arrangement of hooks and barbules primarily for keeping the feather together, such that they prevent air from going through them during the downstroke but allowing some air to pass through in the upstroke, thus maximising the efficiency of energy use in wing flap. The keratin itself has an extremely high specific strength, and the shape of the filament cross sections used in rachis construction moves from near circular near the root to a curved and ribbed rectangular shape away from the root for structural efficiency under bending and potentially buckling loads. The evidence is consistent with the design thesis both from the fossils found of flight in the past, and in the multifunctional nature of wings today

Fossil evidence 
It is evident that the hook and ridge system is a key feature of the barbule system connecting the barbs of a feather. How this came about has been the subject of a number of speculative conjectures in the scientific literature. Laudable indeed have been the attempts to find the evolutionary engine to provide specific function, but the attempt is not impressive, since the array of simpler structures is difficult to imagine, let alone find in the fossil record. Prum takes the view that the forerunner of the pennaceous feather could have been a conical papilla similar to a hair arising out of a cylindrical follicle within the skin. It is then proposed that the papilla became a tuft of barbs (unbranched filaments), and then each of these filaments eventually branched into the barbules. And then, finally, it is maintained that the branched filaments became organised around a central stem (rachis) to produce the hook and ridge structure of present-day feathers. However, the real issue is not addressed by any of these studies. By definition, the Darwinian evolutionary ‘mechanisms’ (which Dawkins summarised as ‘non-random survival of randomly varying hereditary instructions for building embryos …’) have no sense of overall future gain other than the immediate next step. These authors look for evidence that true feathers developed first in small non-flying dinosaurs before the advent of flight, possibly as a means of increasing insulation for the warm-blooded species that were emerging. Though attempts have been made to suggest that the Liaoning shales in Northeast China provide evidence of early feathers on dinosaurs, the hard evidence of clear examples of an intermediate intricate barbule system (hook and ridge) in the vanes has not yet been produced. Xu et al. refer to structures made from filaments of skin in fossils of Sinornithosaurus millenii, a non-avian theropod dinosaur in sediments that are classically dated as about 125 million years old. Though there is evidence of a downy structure, flight feathers were not apparent. What is actually known from the hard fossil evidence (rather than speculation) is that there certainly were now extinct creatures which also had feathers. Archaeopteryx clearly had fully developed flight feathers and the species Microraptor gui shows every evidence of being simply another perching extinct bird, though the feathers are not as distinct as those in Archaeopteryx. A better example is the early Cretaceous Hongshanornis longicresta from the lower Jehol group in the Yixian formation in Northeast China. This example does have barbed feathers and thus falls again into the category of an extinct bird. Thus, the actual evidence shows that one either has extinct fully developed feathers (Archaeopteryx, Hongshanornis, possibly Microraptor gui) or small reptilian  

The details of the sophistication involved in the barb system of the pennaceous feather become clear under a microscope. In Fig. 3, barbules can be seen coming from each barb. 

No evidence for the evolution of birds, feathers, and flight Feathe11
Figure 3: The hooked and ridged structure of barbules in a pennaceous feather.

They are only visible at the micro level, but have a structure that is essential for feathers to work as aerodynamic surfaces. The barbules in one direction are ridge-like, while the barbules in the opposing direction have hooks. Consequently, the hooks of the barbule in one direction grip the ridge of the opposing barbule.

Evolutionary arguments of feather morphogenesis 
Alongside the paleontological studies involving the search for clear transitional fossil evidence, there have been attempts to analyse molecular mechanisms in supposed feather-branching morphogenesis. Yu et al. delivered exogenous genes to regenerate flight follicles in chickens and identified a critical protein necessary in feather branching. They suggest that this identifies molecular pathways underlying possible transformations of feathers from cylindrical epithelia to hierarchical branched structures. Two alternative routes are discussed. The first is by suggesting that the rachis evolved, then the barbs and finally the barbules. The other view of Wu et al.  is that barbs appeared first from supposed integument evolution, followed by a fusing of the barbs to form a rachis. However, in all these investigations, it is still speculation governing such evolutionary hypotheses, since a critical protein has yet to be identified in the formation of feathers. The reality is that there is a fully formed structure of ridged and hooked barbules in all pennaceous feathers and these are found with precise function and position in the wings of birds. So, the rigorous examination of the evidence points rather towards functional complexity coming from intelligence – to suggest that this came about only through the workings of natural selection and random mutations is, in the view of this author, not consistent with the evidence. One of the points which is important is that it is not sufficient to simply have barbules to appear from the barbs but that opposing barbules must have opposite characteristics – that is, hooks on one side of the barb and ridges on the other so that adjacent barbs become attached by hooked barbules from one barb attaching themselves to ridged barbules from the next barb (Fig. 4). It may well be that as Yu et al. suggested, a critical protein is indeed present in such living systems (birds) which have feathers in order to form feather branching, but that does not solve the arrangement issue concerning lefthanded and right-handed barbules. It is that vital network of barbules which is necessarily a function of the encoded information (software) in the genes. Functional information is vital to such systems. 

Functional information 
Some authors assert that possible modes of functionality increase with the rise in ‘Shannon information’ (Shannon information equates with the uncertainty of states of an ensemble of microsystems) and that natural selection then selects out the functioning alternative valid for that environment. They appeal in particular to autocatalytic systems, self-organising systems and pattern formation to form primal replicators from which functional complexity then emerges as natural selection sifts the ensemble of alternatives to single out the replicator with functional advantage. Ball developed these ideas and put greater detail into the arguments by showing convincingly that pattern formation arises from the autocatalytic feedback chemical systems. The Turing patterns in the chlorite–iodide–malonic acid reaction are an example of dissipative structures in reaction–diffusion equations. These type of non-linear systems are connected to the patterns that emerge, such as giraffe and zebra pelts. Most are of the view that he is very likely correct and this author agrees. There can  be no doubt that the work of Murray and co-workers of many years  has done much to elucidate the role of reaction-diffusion mechanisms for formation of patterns in living systems. The well-known Turing reaction-diffusion equation predicts accurately the distribution of surface markings in animals, and the target patterns of the Belousov–Zhabotinskii chemical reaction (involving cyclic AMP, that is, cyclic adenosine monophosphate) are well simulated by the Field–Noyes mathematical model. Furthermore, the periodic patterns of feather germs can also be predicted using similar mathematical principles. However, correct and enlightening as these models are, it is important to recognise that this is not the same as functional information, where coded instructions are involved, first, in the precise ordered arrangement of nucleotides in DNA, and, secondly, in the multifunctioning construction of items from these codes such as hooked and ridged feather barbules. This is a subject of a separate paper by the author where the argument is made that all living systems have coded machinery which sits on high free energy bonds, all of which have to be in place for the system to work. That is, the natural tendency is for the linkages needed for those coding systems (e.g. nucleotide bonds) to decay, and not to be sustained without prior information within the system. Thermodynamically, the very material on which the coded information sits is acting against the natural law which, were it not for the information in the system, would have it fall apart. This strongly suggests that the information, far from being thought as material, is in fact non-material (like the coded instructions of software on a computer) and itself constrains the matter and energy of the nucleotide bonds to perform as they do in DNA. This is certainly the view of other authors and a very cogent statement of this position comes at the end of the paper (conclusions) by Abel and Trevors:

S.C. BURGESS MULTI-FUNCTIONING AND MULTI-OPTIMISATION IN FEATHERS 2007 2

Natural organisms often have multiple functions and multi-optimisation in a single component or mechanism. In addition, natural organisms are highly integrated assemblies. In contrast, human design has traditionally avoided multi-functioning in single components because of the difficulties this presents in the design process. Only in recent years has there been a trend towards multi-functioning in engineering components. The advantage of multi-functioning is that extremely high levels of performance can be achieved. This paper gives examples of multi-functioning and multi-optimisation in a bird flight feather and a bird display feather. In each case, the advantages of multi-functioning are explained and analogies with man-made design are given.

INTRODUCTION 
One of the interesting characteristics of natural organisms from a design point of view is the existence of multiple functions and multi-optimisation in a single component or mechanism. In addition, natural organisms are highly integrated assemblies with several sub-systems being closely integrated together. In contrast, human design has traditionally avoided multi-functioning in single components because of the difficulties this presents in the design process. Multi-functioning and multi-optimisation are very challenging because there are more constraints in the design process and therefore fewer possible solutions. In practice, multi-functioning leads to a need for very sophisticated design solutions. When designing an engineering device, it has traditionally been recommended to design each component for one main function in order to make the behaviour of the device easier to understand and predict. For example, in material selection methodology it has traditionally been assumed that components generally have one main function. Another reason for avoiding multi-functioning in the past is the lack of multidisciplinary design teams and a lack of suitable technology. Observations of past engineering devices show that they do indeed generally possess limited multi-functioning and integration of parts. Only in recent years have engineers adopted a design philosophy of integrating different functions together in single components and mechanisms. For example, cars are becoming highly integrated, with computing hardware and software being closely integrated with mechanical sub-systems such as engines and braking systems. Multi-functioning and integration have obvious benefits. The number of components in a device can be dramatically reduced and this can lead to compactness and low mass. Compactness and low mass can lead to many improved aspects of mechanical performance such as energy and space efficiency and speed of operation. Low part count can also lead to high levels of reliability and easier maintenance. Integration and multi-functioning are very common in nature. Leonardo da Vinci was one of the first scientists to appreciate how the natural world contained optimal design. After studying many aspects of the natural world, 


Leonardo concluded: ‘Although human genius through various inventions makes instruments corresponding to the same ends, it will never discover an invention more beautiful, nor more ready nor more economical than does nature, because in her inventions nothing is lacking, and nothing is superfluous 3

D’Arcy Thompson (1860–1948) was one of the first modern scientists to systematically study optimum design in nature. In 1917 he published his classic work On Growth and Form. More recently, there has been a growing interest in optimum design in nature and its possible application to engineering design. It is very useful to study multi-functioning and multi-optimisation in nature because lessons can be learnt about how to achieve these desirable attributes.

This paper gives examples of multi-functioning and multi-optimisation in a bird flight feather and a bird display feather. In each case, the advantages of multiple functions are explained and analogies with man-made design are given.

MULTI-FUNCTIONING IN BIRD FLIGHT FEATHERS 
The structure of a flight feather is shown in Fig. 1. 

No evidence for the evolution of birds, feathers, and flight Feathe13
Figure 1: Structure of a flight feather. 

There is a hierarchy of structures. The main feather stem comes first, then the barbs and finally the barbules. The stem has a massed array of barbs on each side that form the basic feather shape. Each barb itself has two sets of barbules. The barbules on one side have a set of hooks whilst the barbules on the other side are plain. Therefore, the hooked barbules can interlock with the plain barbules on the adjacent barb. The flight feathers of birds can be considered to have three major functions: an aerodynamic function, a fail-safe function and a lightweight structural function. These functions are summarised in a function-means tree in Fig. 2. 

No evidence for the evolution of birds, feathers, and flight Feathe14
Figure 2: Function-means tree for a bird flight feather. 

A function-means tree summarises the functions and solutions of a device at different levels of detail and shows where multi-functioning takes place. The function means tree in Fig. 2 shows that certain features of the feather are optimal for more than one function. In particular, the hierarchical structure is optimal for all three functions and hence is a very important feature. Despite having three complex functions, the feather is a single integrated structure. 
Optimal aerodynamic layout The overall asymmetric feather profile is optimal from an aerodynamic point of view because the barbs are very short on the leading edge and are therefore protected against buckling from the airflow. Another important aerodynamic feature is a one-way airflow mechanism at each barbule joint. The hooks and barbules are arranged so that they prevent air from going through them when the wing is pushed downwards, but they allow some air to pass through them when the wing is being pulled upwards.

This feature enables the bird to maximise the efficiency of flapping by making the wing mainly push the air down. 

Optimal fail-safe mechanism 
The flight feather of birds contains a localised fail-safe mechanism in the hook structure of the barbules. If the barbs are overloaded then they will unzip from adjacent barbs before any serious damage is done to the feather structure. Once unzipped, the barbs can be re-zipped together by the simple action of the bird passing its beak through the feather. The large number of separate zipping mechanisms ensures that the feather will unzip very close to the point of overload, thus causing minimum damage to the feather. The optimal fail-safe feature of the barbule connections leads to a high level of reliability in the wings of a bird. 

Optimal structural layout 
The hierarchical layout of the flight feather is optimal from a structural point of view because the feather transfers loads from a surface to a point. A hierarchical tree structure is generally the optimal solution for generating an efficient flow of forces (or heat or fluid) between a point source and a volume or surface. The hierarchical structure of the feather is extremely important because it enables localised hooking mechanisms and fail-safe mechanisms as well as an optimum flow of forces. As well as having an optimal hierarchical layout, the flight feather also has optimal material and shape properties. The feather consists of thin-walled keratin sections filled with lightweight foam.

CONCLUSIONS 
One of the main reasons for the exceptional performance and sophistication of bird feathers is the feature of multi-functioning. The design of bird feathers demonstrates that multi-functioning and multi-optimisation can produce large benefits in performance. Not surprisingly, there has been a recent trend in engineering design to move towards multi-functioning in single components and structures. The hierarchical structure of feathers is one of the key features that enable multiple functions to be carried out in one integrated structure. The hierarchical structure enables fine-tuning of shapes and layout and enables a very large number of localised sub-mechanisms to exist. Hierarchical structures have been found to be important in other natural systems such as trees and many other systems in nature. Multi-functioning and multi-optimisation are very challenging because there are more constraints in the design process and hence fewer possible solutions. In addition, the design team must have wide cross-discipline knowledge to know what is feasible and optimal. Nature can be a rich source of ideas and inspiration that can help to achieve multi-functioning in engineering. Multi-functioning in nature can be studied using methods such as function-means trees. Function means trees are a good way of analysing multi-functioning because they help clarify aspects of the solution that are optimal for more than one function. Function-means trees are also good for considering functions of different disciplines such as industrial design (aesthetics) and engineering.


1. https://www.witpress.com/elibrary/dne-volumes/4/2/399
2. https://www.witpress.com/elibrary/dne-volumes/1/1/190
3. http://web.mit.edu/4.464/www/Selection-Vol20No1.pdf
da Vinci L. Manuscript RL 19115v; KrP 114r located in the Royal Library, Windsor Castle, Windsor, England, ca. 1500.



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University of Southern California Researchers show how feathers propel birds through air and history NOVEMBER 27, 2019

Birds of a feather may flock together, but the feathers of birds differ altogether.
New research from an international team led by USC scientists set out to learn how feathers developed and helped birds spread across the world. Flight feathers, in particular, are masterpieces of propulsion and adaptation, helping penguins swim, eagles soar and hummingbirds hover.
Despite such diversity, the feather shares a common core design: a one-style-fits-all model with option trims for specialized performance. This simplicity and flexibility found in nature holds promise for engineers looking for better ways to build drones, wind turbines, medical implants and other advanced materials.
Those findings, published today in Cell, offer an in-depth look at the form and function of a feather based on a comparative analysis of their physical structure, cellular composition and evolution. The study compares feathers of 21 bird species from around the world.
"We've always wondered how birds can fly in so many different ways, and we found the difference in flight styles is largely due to the characteristics of their flight feathers," said Cheng-Ming Chuong, the study's lead author and a developmental biologist in the Department of Pathology at the Keck School of Medicine of USC. "We want to learn how flight feathers are made so we can better understand nature and learn how biological architecture principles can benefit modern technology."
To gain a comprehensive understanding of the flight feather, Chuong formed a multi-disciplinary international team with Wen Tau Juan, a biophysicist at the Integrative Stem Cell Center, China Medical University in Taiwan. The work involved experts in stem cells, molecular biology, anatomy, physics, bio-imaging, engineering, materials science, bioinformatics and animal science. The bird species studied include ostrich, sparrow, eagle, chickens, ducks, swallow, owl, penguin, peacock, heron and hummingbird, among others.



No evidence for the evolution of birds, feathers, and flight 71-researcherss
A the asymmetric vane and tapering main shaft of a single flight feather from a goshawk. Credit: Hao Howard Wu and Wen Tau Juan

They compared feathers using fossils, stem cells and flight performance characteristics. They focused on the feather shaft, or rachis, that supports the feather much like a mast holds a sail, bearing the stress between wind and wing. They also focused on the vane, the lateral branches astride the shaft that give the feather its shape to flap the air. And they examined how evolution shaped the barbs, ridges and hooks that help a feather hold its form and lock with adjacent feathers like Velcro to form a wing. The goal was to understand how a simple filament appendage on dinosaurs transformed into a three-level branched structure with different functions.

For birds such as ducks, eagles and sparrows that fly in different modes, the scientists noted significant differences in the feather shaft compared to ground-hugging birds. On the rigid exterior, the shaft cortex was thinner and lightweight, while the interior was filled with porous cells resembling bubble wrap, aligned into bands of various orientations and reinforced with ridges that operate like tiny lateral beams. Together, it forms a light, hollow and buoyant structure to enable flight. Cross-sections of feather shafts of different birds show highly specialized shapes and orientations of the inner core and outer cortex.
"The flight feather is made of two highly adaptable architectural modules, light and strong materials that can develop into highly adaptable configurations," Chuong said.
The researchers discovered two different molecular mechanisms guiding feather growth. Cortex thickness was governed by bone morphogenetic proteins, which are molecular signals for tissue growth. The porous feather interior, or medulla, relied upon a different mechanism known as transforming growth factor beta (TGF-b). Both components originate as stem cells in the bird's skin.
By contrast, feathers in flightless birds were simpler, consisting of a dense cortex exterior that is more rigid and sturdy with fewer internal struts and cells found in flying birds. The features were especially pronounced for penguins, which use wings as paddles under the water.
As part of the study, the researchers looked at nearly 100 million-year-old feathers, found embedded in amber in Myanmar. These fossils show early feathers lacked one key feature that modern birds have. Specifically, the researchers report how fossil feathers had barb branches and barbules, which form a feather vane by overlapping, but not hooklets. The hooklets, which act like clasps to turn fluffy feathers into a tight flat plane for high-performance flight, evolved later. The scientists also identified WNT2B, another growth factor, as the agent that controls hooklet formation. These also originated from epidermal stem cells.
Taken together, the findings show how feathered dinosaurs and early birds could form a primitive vane by overlapping barbule plates, although that wasn't aerodynamically fit to carry much load. As more complex composite features occurred in the wing, it got heavier, so feather shafts became stronger yet more lightweight, which led to stiffer feathers and sturdy wings that powered flight to carry birds around the world.
"Our findings suggest the evolutionary trends of feather shaft and vane are balanced for the best flight performance of an individual bird and become part of the selective basis of speciation," the study says. "The principles of functional architectures we studied here may also stimulate bio-inspired designs and fabrication of future composite materials for architectures of different scales, including wind turbines, artificial tissues, flying drones."



https://phys.org/news/2019-11-feathers-propel-birds-air-history.html

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Addy Pross:  How Was Nature Able to Discover Its Own Laws-Twice? 2021 Jul 12

The striking reality is that nature’s technological achievements, even for simplest life, have far exceeded human technological achievement that we, in our anthropocentric arrogance, take so much credit for. A comparison of human versus natural technological capability is revealing. Take flying for example. The Swiss mathematician, Daniel Bernoulli, uncovered the principles governing flight in 1738 when he discovered the relationship between pressure, density and velocity in a flowing fluid. That understanding eventually led to the Wright brothers taking their first flight almost two centuries later. Nature, however, has been exploiting those same aeronautical principles for millions of years, well before humans existed. Insects, for example, already took to the air some 320 million years ago, and flight would not have been possible without the insect’s ability to accommodate the specific structural and dynamic requirements that derive from those aeronautical principles. More remarkably, nature’s ‘understanding’ of aeronautical principles extends far beyond the ones laid down by Bernoulli. In bees, for example, the principles of flight are particularly complex and go beyond the thrust and lift concepts governing avian and aircraft flight. Careful study of how bees fly has revealed additional forces that come into being through wing rotation and vortex formation, as the short and stubby bee body would not support flight through just wing beating. The fluid dynamics enabling bee flight turn out to be different to those that enable a plane or bird to fly. 

In the common house fly, the above mentioned technological prowess goes even further, demonstrating capabilities currently quite out of reach of human engineers. Flies have mastered the knack of routinely landing on a ceiling upside down, a remarkable aerodynamic feat. The successful inverted landing of a fly depends on a series of several perfectly timed and highly coordinated actions. First, the fly increases its speed, then it undertakes a rapid body rotation, much like a cartwheel, then it proceeds to extend its legs, before finally landing by a body swing that pivots around the legs that have attached to the ceiling, and all of this coordinated with the fly’s visual and other sensory capabilities. Such capability greatly exceeds current robot technology resulting in engineers utilizing high-speed videography of the fly’s inverted landing to learn how the fly carries out such a sophisticated maneuver [5]. Human engineers are not proud—they are more than happy to consult with common house flies to further their technological capabilities! 

1. Addy Pross:  How Was Nature Able to Discover Its Own Laws-Twice? 2021 Jul 12

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