[2012/12/03] Evolution of Flight: A Story Looking for Evidence
Evolution of Flight: A Story Looking for Evidence
Posted on December 3, 2012
An evolutionary dogma is that land dinosaurs evolved into flying birds. When the claims are acid-washed with critical analysis, what evidence remains?
1. Early bird tryouts: One claim going around now is that Archaeopteryx and other “early birds” were poor flyers, implying that they were transitional forms to falcons and hummingbirds that later progressed to perfect the art of flight. PhysOrg, for instance, titled a recent article “Early birds had an old-school version of wings.” Complete with artwork that makes them look awkward, the article is based on analysis of fossils of Archaeopteryx and Anchiornis by Nicholas Longrich of Yale, who examined the feathers and decided they were “configured differently” thereby showing progressive evolution: “Now it’s clear that early birds were more primitive and represented transitional forms linking birds to dinosaurs.” Other than saying so, what did he find? “We can see the wing slowly becoming more advanced as we move from Anchiornis, to Archaeopteryx, to later birds.” OK, but what were his criteria for ranking them?
“Archaeopteryx has this weird design with multiple layers of long flight feathers,” Longrich said. “The dinosaur Anchiornis has tons of simple, strip-like feathers that overlap—the only bird that has anything remotely similar is a penguin.”
That means that early wings probably worked effectively as simple airfoils for gliding, and perhaps for very primitive flapping flight at high speeds, the researchers say. But the feathers on those wings couldn’t separate and twist in the way they do in a modern bird. Low-speed flight and ground takeoff may have been difficult, or even impossible, for them.
But penguins are very advanced birds with feathers well adapted to their habitat. On what basis can Longrich say that these individuals either had specialized feathers for their needs, or represented degenerate stages of feathers, as seen in some modern flightless birds? Instead, he built a progression from feathers on dinosaurs for warmth, then for display, then for gliding, then for flying, without providing the dates or locations that would illustrate an actual progression.
Moreover, he had to tweak the rates of evolution to keep the story flying: “The researchers propose that the wing feather arrangement seen in modern birds may have evolved within a period spanning perhaps a few tens of millions of years and then remained largely unchanged for the last 130 million years.” That seems a case of special pleading, but Nature News gave the work a short, positive statement, and so did Live Science.
Longrich’s original paper appeared in Current Biology, where he and his team proclaimed, “The avian wing represents one of natural selection’s most remarkable inventions” and praised it profusely. After presenting his transitional sequence, though, problems entered to confuse the picture:
There are a number of issues that complicate this scenario. First, the phylogenetic positions of Archaeopteryx and Anchiornis remain uncertain. Most studies recover Archaeopteryx and Anchiornis as successive outgroups to modern birds, but a recent analysis suggests that Archaeopteryx and Anchiornis may be more closely related to the Deinonychosauria. If so, this would require that either the long, asymmetrical remiges shared by Archaeopteryx and modern birds were acquired convergently, or that the short and symmetrical remiges of Anchiornis are derived. It could also mean that the multitiered feather arrangement is derived for an Archaeopteryx–Deinonychosauria clade, rather than primitive. Further complicating the scenario presented here is the fact that the dromaeosaurid Microraptor gui also has the long, asymmetrical primaries seen in Archaeopteryx and Neornithes (the morphology of the coverts, however, remains unknown for Microraptor). Microraptor may have independently evolved the advanced feather morphology, or again, Anchiornis may represent a reversal. It is also possible that the derived morphology of the remiges seen in Archaeopteryx and Microraptor is primitive for Paraves, and that Anchiornis actually lies outside of this clade. To resolve these conflicts, we require both a better understanding of maniraptoran phylogeny and new information on the plumage of basal maniraptorans such as Protarchaeopteryx and Caudipteryx.
Curiously, the news articles failed to mention these potentially falsifying problems. Longrich also entertained a “punctuated equilibria” evolutionary scenario: rapid development of flight, followed by 130 million years of stasis. So: all that can be said, based on the evidence is this: “Regardless of the precise scenario invoked, it is clear that Archaeopteryx and nonavian dinosaurs have a wing feather organization that differs from that of modern birds.” If the evidence is that limiting, other “scenarios” could accept these differences without invoking progress sequence from dinosaur to bird.
Then, shockingly, he compared bird evolution to airline engineering, and claimed they are similar:
Strikingly, a pattern of stasis is found in manmade aircraft as well: following rapid advances in aircraft design in the early 20th century, progress slowed in later decades, such that many aircraft designed in the mid-20th century still operate. The processes behind the evolution of vertebrate wings and aircraft wings may be the same. The constraints imposed by fluid mechanics mean that a relatively small number of possible wing configurations are effective airfoils; once these geometries are discovered either by natural selection or aeronautical engineering, only small refinements are possible.
The irony was apparently lost on Longrich’s team that engineers work by intelligent design, not by natural selection. If the constraints of physics mean only working machinery will fly, how could he claim that natural selection is capable of what engineers took decades of intelligent planning to execute? The popular science articles left this flawed argument from analogy out, too.
2. Composite explanations: A very confident-sounding article by Michael Balter in Science Magazine on Nov. 2 was titled, “Flying Dinos and Baby Birds Offer New Clues About How Avians Took Wing.” It began,
Most scientists agree that birds are living dinosaurs, survivors of the mass extinction that did in all other dinos at the end of the Cretaceous period 65 million years ago. Birds are also the result of a remarkable series of evolutionary events that transformed dinosaurs from mighty masters of the land into light and feathery lords of the skies. At a meeting of vertebrate paleontologists here last month, researchers pondered fresh clues about the origins of flight from studies of feathered dinosaurs and baby birds.
The “most scientists agree” statement is, of course, a mere appeal to authority and bandwagon arguments. Discounting those, what evidence did Balter present? The said “baby birds” are none other then Ken Dial’s partridge family chicks he’s been promoting for nearly a decade (see (1/16/2003, 12/22/2003, 5/01/2006, 1/25/2008, 6/26/2011). Critics could argue that looking for evolutionary clues from living birds is a throwback to Haeckel’s Recapitulation Theory (2/18/2011#4, 10/31/2012), a technical foul in modern evolutionary theorizing. And since bird chicks come with the genetic program to make them extend their wings in preparation for a life of flight, it would seem nothing could be said about how unobservable dinosaurs behaved – and even if they extended their flightless arms, a mechanism that doesn’t get the genetic mutation for this behavior into the gametes could be criticized as Lamarckian.
Other than that, Balter’s report included a dispute about whether Microraptor was a flyer or glider, or a transitional form from dromeosaurs at all. Apparently it had enough equipment to fly fairly well, whether or not it had the same turning radius as some modern birds. Kevin Padian entered the fray to criticize the arboreal (tree-down) taint of the discussion. He claims the debate ended in favor of the cursorial (ground-up) theory when none other than Ken Dial introduced his “wing-assisted incline running” hypothesis (WAIR) with the partridge family. Thomas Holtz thought that makes “evolutionary sense” because “there would have been selective pressure to ascend into the trees and then get out of them once you got up there.” No evidence was cited that it really happened that way.
Ashley Heers came prepared to respond to criticisms that WAIR conjures up the ghost of Recapitulation Theory – but did she succeed?
In Raleigh, Dial’s graduate student Ashley Heers argued in a widely applauded talk that paleontologists should search for clues to the origins of flight by studying the stages that young birds go through as they begin to fly. Although the 19th century idea that “ontogeny recapitulates phylogeny” has been widely discredited, Heers said, many young animals do retrace key evolutionary steps between birth and adulthood. For example, she argued, young birds such as chukars, a member of the partridge family, have many features that are typical of extinct carnivorous dinosaurs but are not present in adult birds. They include unfused thoracic vertebrae and a small pelvis and very small keel, an extension of the sternum that protrudes outward from the ribs. Young chukars and other juvenile birds also have symmetrical feathers that give way to asymmetrical ones in adult birds, a pattern that reflects differences between early and later feathered dinosaurs. And Heers and Dial have documented wing-assisted incline running in baby chukars; although they cannot yet fly, if their wings are clipped or blocked, their ability to run up inclines is greatly reduced.
This sounds like she rebuked Recapitulation Theory only to embrace it. If she had a response to the fact that baby birds have a genetic program to fly, while dinosaurs did not, Balter didn’t report it. Yet her presentation was “widely applauded,” he did notice.
3. Heavy-set pre-birds: Other than mentioning imaginary feathers, another article on Science Daily avoided the question of the origin of flight while undermining a different evolutionary assumption: the idea that bigger is better. “For Some Feathered Dinosaurs, Bigger Not Always Better,” the headline reads. The falsifiable notion in question was whether diet contributed to dinosaur size. “Now researchers have started looking at why dinosaurs that abandoned meat in favor of vegetarian diets got so big, and their results may call conventional wisdom about plant-eaters and body size into question.”
“The largest feathered dinosaurs were more than 100 times more massive than your average person,” says Zanno. “The reality is that for most of us, it is downright difficult to imagine a feathered animal of gigantic proportions.”
Apparently it takes a scientist who has practiced imagination to get good at it. Anyway, a simplistic, clear-cut “evolutionary advantage” toward larger size disappeared in the data. “They found that these theropod groups were experimenting with different body masses as they evolved, with some getting bigger, while others were getting smaller,” the article anthropomorphized. “In short, there was no clear-cut drive to get big — size seemed to provide no overwhelming advantage during the evolution of these animals.” Flight was certainly not on their experimental curriculum.
4. All praise to natural selection’s engineering perfection: Perhaps the most jaw-dropping juxtaposition of praise for engineering design and for natural selection can be seen in a recent paper in the CEAS Aeronautical Journal. First, here’s what Hans Försching and Holger Hennings have to say about the power of evolution:
Avian flight is one of the remarkable achievements of vertebrate evolution.… The enigmatical flight of birds with their inimitable flight capabilities has at all times attracted our attention. Flying animals have populated the sky already since more than hundred million years. Here, the birds evolved in their long evolution, from dinosaurs to bipedal feathered flying reptiles, to perfect flight machines of nature. They dominate in exemplary manner the fundamental requirements for an efficient flight—propulsion, aerodynamic lift, flight stability and control, and extreme lightweight construction. Thus, in the early pioneering time of aircraft design, birds were the pilot instructors of the Homo sapiens in his efforts to realise the ancient human dream to fly, finally with the aid of technical resources.
That’s essentially all they had to say about evolution. But then, in their conclusion, they waxed nearly ecstatic about the design perfection in avian flight:
The study demonstrates conclusively, that concealed aeroelastic effects contribute essentially to the marvellous flight capabilities of birds. Certain structural wing asymmetries and specific anatomic peculiarities of the bony wing skeleton play thereby a fundamental role. An extremely precise coordination of the complex wing beat motions, together with a perfect flight guidance and control performance, are additional basic requirements for an efficient active flight. The birds dominate all of these requisites in a masterly manner. In a flight-mechanical control circuit, the large flight muscles, and many others in the wing, serve as actuators, the extremely marked sense organs act as flight sensors, and the extremely developed cerebellum takes the function of a computer as guidance and control centre. These biological elements communicate with lightning speed like an autopilot as a biotechnical marvel with unimaginable precision. Thus, the birds can precisely adjust and control their flight in all styles and situations without flow separation in a stable flight-mechanical and aeroelastic equilibrium. With their spectacular flight capabilities, birds are really the inimitable flight artists of nature. They are equipped with unique flight skills, all mysteries of which are obviously still not yet completely known.
No Darwinian aftertaste in that paragraph.
Darwinists are a club of ideologues whose mission is to maintain a naturalistic “scenario” at all costs, even if it means committing various evolutionary no-no’s, such as (1) Recapitulation Theory, (2) Lamarckism, (3) Just-So Storytelling, and other no-no’s for general science like (4) big lie, (5) half-truth, (6) non-sequitur, (7) card stacking, etc. (see all the tricks of the trade in the Baloney Detector). Observations are mere props to keep their story going. It’s not that they are blind to the evidence; they are without excuse, because it is clearly seen all around them (Romans 1:16–25), even overhead in a passing flock of birds. Because they know design in their hearts, they hate everyone who points it out. Pray for them.