Flightless Bird Wings | Berean Archive

"The span of time needed to evolve flightlessness in rails can probably be measured in generations rather than in millennia." (Storrs Olson, Smithsonian Contributions to Zoology, 1973)¹

"They derived from smaller birds that once could fly. This is possible in the creationist model. Loss of features is relatively easy by natural processes" (Jonathan Sarfati and Don Batten, Creation Ministries International, 2006)²

Summary

The parent article, Vestigial Structures, separates the dead claim that a vestige is useless from the live claim that it is a reduced copy of something fuller in an ancestor, and tests the live claim in three steps: homology, reduction, and an ancestral distribution on a tree built from other characters. Flightless birds are the one case in the set where the third step is not in dispute, because the creationist literature itself says these birds descend from fliers.

What the wings are. The ostrich's wing skeleton is about 67 cm long,³ and the bird uses the wing as an air rudder and brake at speed, in courtship and distraction displays, and to shelter chicks.⁴³ The emu wing is "vestigial, with no known function," with one digit.⁵ The kiwi wing is a stub with a claw of 3 to 18 mm that still carries the two skin folds of a flying wing.⁶⁶ The moa had no wing, only a finger-sized shoulder bone.⁷ The Galapagos cormorant's wing is 19 cm against 31.5 cm in its closest relative, on a bird 1.6 times heavier, with no digit or muscle missing.⁸⁹
Function is real and settles nothing. The modern vestige claim is about reduction from an ancestor, and a demonstrated use never reaches it. Coyne's "Tiny, nonfunctional wings" is the old argument, and his own book grants the ostrich wing's uses seven pages earlier.¹⁰¹⁰
Homology and reduction are measured. Every flightless wing examined has the flying wing's parts at smaller scale: the cormorant's full set of flight feathers at half length,⁹ the emu's single digit, the moa's shoulder remnant. The flightless takahe's wing loading is 2.98 g/cm², above Meunier's 2.5 g/cm² ceiling for flight.¹¹¹¹
Ancestry is agreed. Twenty nuclear genes put the flying tinamous inside the ratites, so flight was lost at least three times among them,¹² and ancient DNA implies "every major ratite lineage independently lost flight."¹³ Rails, ducks, the cormorant and the kakapo each sit among flying relatives. CMI's ostrich article: "Many creationist biologists think that most flightless birds, if not all, had flying ancestors," and "they are in general agreement with evolutionists."¹⁴
How, and how fast. The Galapagos cormorant carries a fixed 12-base-pair deletion in the gene for the transcription factor CUX1, plus variants in genes whose mutation causes skeletal ciliopathies in humans and mice, and it split from its flying relatives about two million years ago on the mainstream clock.⁸⁸⁸ The ratite genomes show 2,355 independent accelerations of conserved noncoding DNA along flightless lineages.¹⁵ A flightless rail is a chick's skeleton kept into adulthood;¹ the Aldabra rail lost flight within at most 80,000 to 130,000 years, and did so twice;¹⁶¹⁷ and the flying and flightless steamer ducks of the Falklands are "genetically indistinguishable."¹⁸
The creationist replies. Sarfati and Batten give three possibilities: descent from fliers, function, and "design economy."² The first concedes all three steps. The second answers only the useless claim. The third predicts wings on every bird, which descent predicts too, but not why the reduced ones nest inside flying families. The Institute for Creation Research's 2022 article denies that flightlessness is a mutation and does not mention the cormorant genome.¹⁹

Verdict: flightless bird wings pass the vestige test at every step, and creationist authors concede the ancestry. The case proves that flight is lost by identifiable genetic changes, quickly and repeatedly, inside families that still fly. The young-earth devolution model predicts that, and so does natural selection. It proves nothing beyond the family: the ratite tree reaches the palaeognaths, a group of several orders that creationist authors already treat as possibly one flying kind, and no flightless bird's wing says where birds came from.

Part 1: What the wings are and do

Ratites and the moa

Brian Bertram's field study of wild ostriches in Tsavo, Kenya, says on its first page: "Ostriches' wings are considerably reduced."⁴ Then: "The wings are used for a variety of display purposes in addition to their function in controlling the bird's temperature, in counterbalancing during fast manoeuvring, in protecting eggs and young, and in whisking away flies."⁴ In courtship the squatting male "waves his quivering spread wings alternately in the air";⁴ near a nest the bird scuttles away "with wings low and flapping irregularly, and then collapsing on the ground."⁴

Nina Schaller's 2008 Heidelberg dissertation is the only study found that treats the ostrich wing as a running aid. Watching four hand-raised adults for three years, she found that the bird "uses its relatively large wings as an 'air-rudder' by quickly extending them while running."³ Because the hip and knee barely move sideways, "ostriches are largely unable to execute small radius turns at running speeds without the use of their wings,"³ and to stop, the bird can "swiftly extend both wings to present a very large surface area to arrest forward motion".³ The wing skeleton is "~ 67 cm", "featuring a humerus as long as 43 cm".³ Two cautions. Schaller says of her own wing chapter, "It must be understood that these observations are not the result of systematic data gathering,"³ and no paper was found that measures how much heat the wings shed. Bertram credits ostrich temperature control to feather erection and panting, citing physiology papers, and asserts the wing's thermal role without a measurement.⁴

The other ratites grade downward. Schaller told the Society for Experimental Biology in 2010 that rheas "use their wings to maintain balance" when zigzagging, while "the Australian emu and the Cassowary have very small wings which they hold very tightly to their body and are not used in locomotion."²⁰²⁰ Farlie and colleagues' 2017 developmental study: "The mature wing of the emu is vestigial, with no known function, and exhibits a substantially reduced and morphologically highly variable wing with an autopod harboring a single digit. In contrast, the ostrich and rhea possess functional wings with strongly reduced zeugopod and autopod harboring three digits."⁵

The kiwi's wing is a stub hidden in the plumage. T. Jeffery Parker, describing kiwi anatomy for the Royal Society in 1891, found that it still carries "a true alar membrane," with "a distinct fold of skin, or pre-patagium, passing between the upper arm and fore arm, as well as an equally well marked fold, the post-patagium, between the postaxial border of the upper arm and the trunk."⁶⁶ He took this as evidence "in favour of the derivation of Apteryx from a progenitor with well developed wings." The claw at the tip runs from 3 mm in one species to 18 mm in another, and is "constantly larger in the male than in the female, and often differs on the two sides of the body."⁶ Coyne calls these wings "functionless nubs."¹⁰

The moa is the end of the series. Huynen and colleagues, who recovered the moa's forelimb gene tbx5 from ancient DNA, write that the moa "are unique in having no skeletal evidence of forelimb-like structures," and that "The only evidence that moa once had wings is the presence of a small finger-sized bone, the scapulocoracoid, a fused remnant of the forelimb girdle's coracoid and scapula".⁷⁷ The gene itself still worked: "Moa Tbx5 is identical to chicken Tbx5 in being able to activate the downstream promotors of fgf10 and ANF."⁷

The Galapagos cormorant

Burga and colleagues' 2017 genome paper describes the bird: "P. harrisi has a pair of short wings, which are smaller than those of any other cormorant," and "The radius and ulna are disproportionally small compared to the humerus, but no digits have been fused or lost".⁸ It also has "underdeveloped pectoral muscles," "a 1.6-fold increase in body mass, and a highly reduced keel."⁸ The numbers: "The average wing length of an adult Galapagos cormorant male is 19 cm (3.6 kg. body mass), whereas the wing length of its closest relative, the double-crested cormorant, is 31.5 cm. (2.2 kg. body mass)."⁸

Bradley Livezey's 1992 monograph, their reference (7), measured the reduction against eight flying cormorants. Wing loading in the flying species "ranged from 1.0 to 1.7" g/cm²; the Galapagos bird's is 5.1.⁹ "The small wings of C. harrisi result from an c. 50% shortening of remiges," and "Numbers of primary and secondary remiges in C. harrisi remain unchanged."⁹ On dissection, "No muscles or parts thereof were lacking in the pectoral limb of C. harrisi".⁹ Every part of a flying cormorant's wing is present, at about half size, on a bird nearly twice the weight.

The kakapo, the rails and the steamer ducks

The kakapo is a parrot with, in Livezey's words, "the smallest relative wing size of any parrot," a "vestigial carina" on the sternum and "a greatly reduced Mm. pectoralis thoracica and supracoracoideus," the two flight muscles.²¹²¹ Gill measured its wing loading at 1.62 g/cm² in 2023, with the flightless weka at 1.19 and the South Island takahe at 2.98, against Meunier's theoretical flight ceiling of 2.5.¹¹¹¹ A flying mute swan carries 1.70,¹¹ so the weka and kakapo are flightless at loadings some flying birds exceed. Wing loading alone does not decide the matter; the missing keel and flight muscles do.

Rails are the great losers of flight. Storrs Olson's 1973 monograph on the South Atlantic rails counts the family as "roughly a quarter of which living or recently extinct members have lost the ability to fly,"¹ and describes the condition: "The elements of the wing and shoulder girdle and the sternum are reduced relative to the size of the body and hindlimbs. The depth of the carina sterni is reduced, often drastically."¹ Darwin's "logger-headed duck of South America," which "can only flap along the surface of the water, and has its wings in nearly the same condition as the domestic Aylesbury duck,"²² is the steamer duck, Tachyeres, "four species, three of which are flightless."¹⁸

Penguins

Penguins enter the argument through Coyne: "why would a creator use exactly the same bones in flying and flightless wings, including the wings of swimming penguins?"¹⁰ That is a homology claim, not a reduction claim: the flipper is a wing rebuilt for water, not a weaker one. Olson excluded penguins in 1973: "Their outstanding adaptations are for flying through a medium many times denser than air and are much different from other flightless birds; in a sense, these birds are the best fliers of all."¹ Elliott and colleagues measured why in 2013: flight costs in murres, which fly and swim with one wing, "are the highest recorded for vertebrates," so "optimizing wing shape and form for wing-propelled diving leads to such high flight costs that flying ceases to be an option in larger wing-propelled diving seabirds, including penguins."²³²³ A penguin's wing is not a vestige on any definition, and the rest of this article leaves penguins out.

Part 2: The three-step test

Step 1, homology

Nobody disputes it, and the anatomy is the reason: Parker's kiwi wing has the patagia of a flying wing; Livezey's cormorant wing has every muscle and every flight feather; Burga's cormorant has lost no digit; Farlie's emu has one digit where the ostrich and rhea keep three; Huynen's moa has a scapulocoracoid and nothing else. Sarfati and Batten's first possibility, "They derived from smaller birds that once could fly," assumes the homology, and their third, "In using the same embryological blueprint for all birds, all birds will have wings," asserts it.²²

Step 2, reduction

This is the step where vestige claims are usually loosest, and here it is numerical. The cormorant's wing is 60 percent of its closest relative's length on a bird 64 percent heavier, with flight feathers half as long and wing loading three to five times higher. The takahe's wing loading is above the flight ceiling. The emu has one digit; the moa had no wing. Darwin noted in 1859 that rudimentary organs "are very liable to vary in degree of development,"²² and Parker's kiwi claws, which differ between sexes and between the two sides of one bird, and Farlie's "morphologically highly variable" emu wing fit that description.⁵

Reduction is also visible before it is complete. Wright, Steadman and Witt measured 366 island populations of flying birds in 2016 and found that "smaller flight muscles and longer legs evolved in response to increasing insularity and, strikingly, the scarcity of avian and mammalian predators."²⁴ They count the end point: "More than 1,000 independent lineages of island birds have lost flight, including rails, parrots, pigeons, owls, waterfowl, and passerines".²⁴ Fulton, Letts and Shapiro's steamer ducks show the gradient inside one genus: "Each lineage of Tachyeres represents a different stage between flight and flightlessness."¹⁸

Step 3, ancestry, and why creationists agree

The third step asks whether the reduced state is the derived one on a tree built from characters other than the wing. For island birds Darwin gave the answer in 1859: "the nearly wingless condition of several birds, which now inhabit or have lately inhabited several oceanic islands, tenanted by no beast of prey, has been caused by disuse."²² A flightless rail on an atoll has a flying rail on the mainland for its nearest relative, and the Galapagos cormorant has a flying cormorant on the coast of the Americas. Darwin's ostrich story was disuse too: as the body grew, "its legs were used more, and its wings less, until they became incapable of flight."²²

For the ratites the question stayed open until 2008, because one flightless ancestor on Gondwana was the textbook story. Harshman and seventeen co-authors sequenced twenty nuclear genes and found "a genome-wide signal that unequivocally places tinamous within ratites, making ratites polyphyletic and suggesting multiple losses of flight." Their conclusion: "The most plausible hypothesis requires at least three losses of flight".¹²¹² Mitchell and colleagues' ancient DNA made Madagascar's elephant birds the sister group of the kiwi in 2014, which "strongly suggests that gigantism and flightlessness have evolved multiple times among palaeognaths," and their results "imply that every major ratite lineage independently lost flight".¹³¹³ Cloutier and colleagues' 2019 whole-genome study cites ten studies and says "ratite paraphyly is strongly supported by all recent molecular studies".²⁵ The tree that puts a flying group inside the flightless one was built from genes, not wings, so the circularity objection the parent article discusses does not arise.

The creationist literature accepts this step in its own words. Besides Sarfati and Batten's first possibility, Cosner and Sarfati wrote of the cormorant in 2009: "Not needing to use its wings for flight, its wings have deteriorated in ways that would have been eliminated in flying birds," and "Now we realize that this loss occurred through a mutation, or genetic copying mistake."²⁶²⁶ Answers in Genesis, 2005: "The most likely answer is that its ancestors could fly."²⁷ Eggleton at CMI, 2019, on the ratites: "it is now thought that flightlessness arose independently in the ratites multiple times."¹⁴ Cserhati at CMI, 2019, lists "the great auk, the dodo, the moa, ostrich, rhea, emu, cassowary, kiwi and kakapo" as birds that lost flight.²⁸

So the flightless bird is the one vestige case in this series where homology, reduction and derived state are granted by both sides.

Part 3: How flight is lost, and how fast

The genes

Burga and colleagues sequenced the Galapagos cormorant with three flying cormorant species and found "an overrepresentation of predicted function-altering variants in genes that, when mutated in humans and mice, cause skeletal ciliopathies and bone growth defects," homozygous in twenty birds from two populations.⁸ The strongest candidate is a 12-base-pair deletion in Cux1, a homeobox gene: "We also confirmed that this variant is fixed in the population and absent in the other cormorant species (fig. S10A). The 12 bp deletion in Cux1 removes four amino acids, AGSQ, immediately adjacent to the C-terminal end of the homeodomain".⁸ A truncated form of CUX1 overexpressed in the chick wing "results in severe wing truncation," and in cell lines the cormorant's version was a weaker activator of cilia genes and of cartilage growth.⁸ Their summary of the anatomy: flightlessness "is caused by the retention into adulthood of juvenile characteristics affecting pectoral and forelimb development (a class of heterochrony known as paedomorphosis)".⁸ Ratites and penguins "became flightless over 50 million years ago," while "the Galapagos cormorant and its flighted relatives are estimated to share a common ancestor ~2 MYA".⁸

The ratites show the same at the level of regulation. Sackton and colleagues sequenced eleven new palaeognath genomes, including a moa, in 2019 and found that "convergent evolution of regulatory regions, more so than protein-coding genes, is prevalent among developmental pathways associated with independent losses of flight." Of 284,001 conserved noncoding elements, their analysis "identified 2355 independent accelerations along lineages of flightless paleognaths, with functional consequences for driving gene expression in the developing forelimb."¹⁵ In the emu, Farlie's group found a heart transcription factor switched on in the wing bud "but not in ostrich, or chicken and zebra finch, which have fully developed wings," and proposed "that Nkx2.5 functions to inhibit early limb bud expansion and later muscle growth during development of the vestigial emu wing."⁵ In the moa the master forelimb gene was untouched, so "genetic changes affecting genes other than tbx5 must be responsible".⁷

The developmental route and the rate

Olson saw the mechanism in rails before any genetics: "if the proportions of the skeleton of the younger rail were maintained on into adulthood, the result would be a flightless rail. Thus, flightlessness would not be a result of numerous structural modifications, but a simple retention of a state already present in the young stages of every rail."¹ His abstract adds that it "is evolved at a rapid rate," and that its advantage "is thought to be in the conservation of energy resulting from the decrease in mass of the flight muscles."¹ That is why the same organ goes every time: the change is a timing change in one growth programme, and Wright's island populations are partway along it.

On rate, Olson: "The span of time needed to evolve flightlessness in rails can probably be measured in generations rather than in millennia,"¹ and "Flightlessness, and its correlated adaptations, is easily and quickly evolved".¹ Van de Crommenacker and colleagues dated one case in 2019: the Aldabra rail sits "among the most rapid documented avian flight loss cases (within an estimated maximum of 80,000–130,000 years)," and is still only a subspecies of the flying white-throated rail of Madagascar.¹⁶ Hume and Martill found flightless Dryolimnas fossils in beds laid down before and after the sea-level high-stand that drowned the atoll, "providing irrefutable evidence that a member of Rallidae colonized the atoll, most likely from Madagascar, and became flightless independently on each occasion."¹⁷ Fulton's steamer ducks: "the flying and flightless steamer ducks on the Falkland Islands are genetically indistinguishable," and "The three continental species share a common ancestor approximately 15 000 years ago".¹⁸¹⁸

What the rate cuts

This cuts both ways. Every documented loss is a loss: a deletion, a switched-off enhancer, a growth programme stopped early. None adds a structure. Loss is fast and repeatable because breaking a programme is easy. That is the content of Sarfati and Batten's "Loss of features is relatively easy by natural processes," and the cormorant genome is its best confirmation. It is also the content of Darwin's chapter on use and disuse and of Olson's energy argument; natural selection does not need to build anything to make a flightless rail. Neither model is embarrassed by a fast, repeated, genetically identifiable loss of flight, and the rate of loss says nothing about the rate of gain.

Part 4: The creationist literature, stated and then priced

The three possibilities

Sarfati and Batten's 2006 article lists three possibilities for why "ostriches, emus, etc have wings":²

(a) "They derived from smaller birds that once could fly. This is possible in the creationist model. Loss of features is relatively easy by natural processes; acquisition of new characters, requiring new DNA information, is impossible."²
(b) "The wings have a function. Some possible functions, depending on the species of flightless bird, are: balance while running, cooling in hot weather, warmth in cold weather, protection of the rib-cage in falls, mating rituals, scaring predators (I've seen emus run at perceived enemies of their chicks, mouth open and wings flapping), sheltering of chicks, etc. If the wings are useless, why are the muscles functional that allow these birds to move their wings?"²
(c) "It is a result of 'design economy' by the Creator. Humans use this with automobiles, for example. All models might have mounting points for air conditioning, power steering, etc. although not all have them. Likewise, all models tend to use the same wiring harness, although not all features are necessarily implemented in any one model. In using the same embryological blueprint for all birds, all birds will have wings."²

The article does not say which possibility applies to which bird, and it predates all the genetics above. Eggleton's 2019 ostrich article is CMI's fuller statement: "It's actually very easy for creatures to lose complex abilities such as flight," and "when a genetic accident (mutation) cripples some part of the complex flight machinery, the flightless form, which would normally be eliminated as defective, is very likely to dominate the island population."¹⁴¹⁴ On the boundary: "Hybridization studies, not yet available, could help to determine how many created kinds are within the ratites, and thus how many times flightlessness arose." The late Jon Ahlquist "thought that the genetic data was most consistent with ratites and tinamous having descended from one ancestral (flying) population that came off the Ark. Other creationist researchers think ratites likely represent more than one kind, each originally flying."¹⁴¹⁴

Answers in Genesis is less settled. Donna O'Daniel's 2015 Answers article says "there is no consensus among creationists whether some kinds of birds never flew," and gives the evidence for flying ancestry herself: "the keels of several species seem to be in different stages of deterioration, thus possibly indicating the progressive loss of flight."²⁹ She then reports the other view: "Other creationists believe, however, that certain bird kinds were created by God to be flightless. Their unique and integrated designs, especially ratites and penguins, point to God's special design, not accidents and loss."²⁹

Cserhati's CMI article on the Aldabra rail concedes everything but the word: "Flightlessness is not a characteristic that can be gained, since it involves the loss of a morphological structure"; "It is quite possible that these birds actually lost genetic information (i.e. one or more mutations in homeobox genes, which function in development)"; "This would be a case of devolution and not evolution."²⁸²⁸²⁸ He finds the repetition hard to credit: "The probability of the same organ being affected on different occasions over tens to hundreds of thousands of years in the same species is very small indeed."²⁸

Scott Arledge at the Institute for Creation Research, 2022, is the outlier. He calls the mutation-and-selection account a story that "creationists sometimes come along and repeat," and says "Flightlessness is not a mutation, and it's certainly not designed by wind."¹⁹¹⁹ Rails instead "are engineered to be flightless if needed so they can thrive on a faraway tiny island".¹⁹ He still grants the reduction: "Their wings and related muscles are also reduced."¹⁹

Which claim each reply answers

Possibility (b), the list of functions, answers Darwin 1859 and Wiedersheim 1895. It is correct for the ostrich and rhea and wrong for the emu, whose wing has "no known function," and for the moa, which had none. It does not touch the modern claim, because a working ostrich wing is still 67 cm of flying-wing skeleton on a bird that cannot fly. The question "If the wings are useless, why are the muscles functional" has the same shape: the muscles are the flying bird's muscles, kept.

Possibility (a) answers the homology claim by conceding it, and the rest of the creationist literature has adopted it. It costs the model nothing, because the model already allows loss inside a kind. What it does not do is price the loss. No creationist source found for this article says how many kinds the ratites are, how large the flying ancestor was, or how much regulatory change the ratite accelerations represent. Eggleton says the hybridisation data do not exist. That is the honest state of the creationist account: descent from fliers is granted, and the accounting has not been done.

Possibility (c), design economy, is the only reply that explains the shared bones without descent, so it must be judged on what it predicts. It predicts that every bird, flying or not, will have a wing on the same plan. That is true, and descent predicts it equally. It does not predict that flightless birds will be scattered one or a few at a time inside families that fly; that their wings will be the flying wing at reduced scale rather than a limb built for the ground; that a flightless cormorant will carry a fixed deletion, absent in its flying relatives, in a gene whose altered form truncates the chick wing; or that the emu will run a heart gene in its wing bud. Sarfati and Batten offer (c) as one possibility among three; the evidence since 2006 has made (a) the one that fits, and CMI's later articles say so.

Arledge's engineered-response model has to answer Burga. A twelve-base-pair deletion, fixed in the population and absent in the other cormorant species tested, is a mutation on any definition, and it sits beside the homeodomain of a homeobox gene, the kind Cserhati predicted. "Flightlessness is not a mutation" is not a position the cormorant genome allows. Cserhati's improbability argument has a different problem. Olson showed in 1973 that a flightless rail is a chick's proportions kept into adulthood, and Wright counted more than a thousand lineages that have gone that way, with flying island birds already partway along. The same organ is affected every time because there is one growth programme to stop. Repetition is the expected outcome, not an improbable one.

Objections and responses

Ostrich wings have several functions, so they are not vestigial. On the definition Darwin used, that is right. On the definition the argument has used since 1982, a vestige is a reduced homologue with an ancestral explanation, and the ostrich wing is a 67 cm flying wing on a bird that cannot fly. The functions are real; the claim they answer is not the live one.

Coyne calls flightless wings nonfunctional, and that is false. It is false for the ostrich and rhea, and Coyne's own page 57 says the ostrich wing "has been co-opted for new uses."¹⁰ The inconsistency is his. The argument as the parent article states it does not need "nonfunctional," and this article does not use it.

Loss within a kind is not evolution, so the case proves nothing. It proves the three things the vestige test asks for, and creationists grant all three. It does not prove descent beyond the family, and this article does not claim it. The dispute that remains is where the kind boundary lies, and the flightless birds put it no lower than the family and no higher than the palaeognaths, which CMI's own source treats as possibly one flying population.

Design economy explains the shared bones without descent. It explains the shared plan and nothing else; Part 4 lists what it fails to predict and descent does. A hypothesis that predicts only what its rival also predicts is not an alternative.

Ratites were created flightless. O'Daniel reports this view. It has to explain why the flying tinamous fall inside the ratites on twenty nuclear genes and on whole genomes; why the ostrich and rhea wing carries three digits, a humerus, radius and ulna, and the kiwi's a flying bird's patagia; why the ratite lineages show thousands of independent accelerations in the same kind of regulatory DNA; and why CMI's own writers say most creationist biologists think most flightless birds descend from fliers. Nothing in the anatomy or the genetics supports it.

Rails lost flight fast, which contradicts evolution's millions of years. Cserhati: "the rapidity of flight loss in these birds goes against the standard evolutionary view of millions of years being required for such processes to happen."²⁸ The mainstream sources quoted here say the opposite about loss: Olson in 1973 put it in "generations rather than in millennia,"¹ and Wright calls it "rapid and irreversible."²⁴ Fast loss is agreed. It says nothing about how long gaining a wing would take.

If the case passes, the vestige argument works. For loss inside a family, it does, and this article says so. The inference to universal common descent needs the tree beyond the family, and no flightless bird's wing supplies it. The parent article's whale pelvis and horse splints are where that fight is.

Issues and unanswered questions

The best evidence for ostrich wing use in running is Schaller's 2008 thesis, and she says her wing chapter is "not the result of systematic data gathering." Her proposed wind-tunnel and treadmill experiments appear unpublished. No measured value for the wings' contribution to turning, braking or cooling was found. The abstract of Maloney's 2008 review of ratite thermoregulation credits insulation, metabolic heat and "respiratory evaporative water loss" and does not mention the wings; its full text was not obtained.³⁰
Bolwig 1973, Sauer and Sauer 1966 and Hurxthal 1979, the primary papers on ostrich display, were not obtained; the displays are taken from Bertram 1992, who describes them from his own field study.
Hume and Martill 2019 and Livezey's two 1992 monographs were read at abstract only; the OUP and Wiley copies are paywalled. Sackton 2019 was read from the bioRxiv preprint and the published abstract.
Bergman and Howe's 1990 book, cited by Sarfati and Batten, was not obtained.
No creationist source prices the ratite case: the number of kinds, the size of the flying ancestor, or the amount of regulatory change. Until the hybridisation studies Eggleton calls for exist, the number of ratite kinds is open on the creationist side.
No creationist author was found stating a prediction of "design economy" that descent lacks; if one exists, it belongs here.
Whether a flying ancestor of penguins is known in the fossil record was not researched; the article does not rely on penguins.

Verdict

The wings of flightless birds are reduced flying wings, and they are reduced from ancestors that flew. Homology is settled by the anatomy, reduction by measurement, and ancestry by trees built from genes rather than wings, which put the flying tinamous inside the ratites and every other flightless bird among flying relatives. The creationist literature concedes that these birds descend from fliers. The case passes the parent article's test at all three steps, and it is the strongest passing case in the set.

What it proves is narrow, and both sides should say so. Flight is lost by identifiable genetic changes: a fixed deletion in a homeobox gene, thousands of accelerated regulatory elements, a heart gene co-opted into a wing bud, a growth programme stopped at the chick's proportions. It is lost quickly, within an estimated maximum of 80,000 to 130,000 years for the Aldabra rail and inside one gene pool for steamer ducks, and it is lost again and again. Natural selection predicts that when flight stops paying, and the creationist devolution model predicts it of a fallen creation. The replies that list functions answer a claim the modern argument no longer makes; the reply that grants descent from fliers is correct and unpriced; design economy predicts nothing descent does not; and the denial of mutation is contradicted by the one flightless genome that has been read. None of this reaches past the family. The ostrich's wing says that ostriches came from birds that flew. It does not say where birds came from.

Sources

1.
Olson, Storrs L. “Evolution of the Rails of the South Atlantic Islands (Aves: Rallidae).” Smithsonian Contributions to Zoology 152:1–53. 1973. A 1973 monograph on the rails of the South Atlantic islands, the bird family Rallidae. Its abstract says flightlessness in rails is a neotenic condition, meaning a juvenile trait kept into adulthood, that evolves at a rapid rate and is of limited use for classifying the birds. The article uses it for the share of rails that have lost flight and for Olson's claim about how fast that happened.
1. 1a.
  Section Abstract: “Flightlessness in rails is shown to be a neotenic condition that involves only the control of relative growth of body parts, is evolved at a rapid rate, and therefore has limited taxonomic significance. The evolutionary advantage of flightlessness is thought to be in the conservation of energy resulting from the decrease in mass of the flight muscles.” ↩
2. 1b.
  Page 27: “Flightlessness, and its correlated adaptations, is easily and quickly evolved and is in itself not a useful taxonomic criterion.” ↩
3. 1c.
  Page 31: “Prominent among these is the Rallidae, roughly a quarter of which living or recently extinct members have lost the ability to fly.” ↩
4. 1d.
  Page 31: “(Penguins and the nonvolant alcids should not be included in discussions of flightlessness. Their outstanding adaptations are for flying through a medium many times denser than air and are much different from other flightless birds; in a sense, these birds are the best fliers of all.)” ↩
5. 1e.
  Page 33: “The elements of the wing and shoulder girdle and the sternum are reduced relative to the size of the body and hindlimbs. The depth of the carina sterni is reduced, often drastically.” ↩
6. 1f.
  Page 33: “It is obvious then, that if the proportions of the skeleton of the younger rail were maintained on into adulthood, the result would be a flightless rail. Thus, flightlessness would not be a result of numerous structural modifications, but a simple retention of a state already present in the young stages of every rail.” ↩ ↩
7. 1g.
  Page 34: “The span of time needed to evolve flightlessness in rails can probably be measured in generations rather than in millennia.” ↩ ↩ ↩
2.
Sarfati, Jonathan, and Don Batten. “'Vestigial' Organs: What do they prove?” Creation Ministries International. Feb 14, 2006. A 2006 web article by two writers for Creation Ministries International. The article uses it as the creationist reply on flightless wings: three possibilities for why ostriches, emus and other flightless birds keep wings, of which descent from smaller fliers is the first.
1. 2a.
  “There are at least three possibilities as to why ostriches, emus, etc have wings:”. ↩ ↩
2. 2b.
  “a) They derived from smaller birds that once could fly. This is possible in the creationist model. Loss of features is relatively easy by natural processes; acquisition of new characters, requiring new DNA information, is impossible.” ↩ ↩ ↩
3. 2c.
  “b) The wings have a function. Some possible functions, depending on the species of flightless bird, are: balance while running, cooling in hot weather, warmth in cold weather, protection of the rib-cage in falls, mating rituals, scaring predators (I've seen emus run at perceived enemies of their chicks, mouth open and wings flapping), sheltering of chicks, etc. If the wings are useless, why are the muscles functional that allow these birds to move their wings?” ↩
4. 2d.
  “c) It is a result of 'design economy' by the Creator. Humans use this with automobiles, for example. All models might have mounting points for air conditioning, power steering, etc. although not all have them. Likewise, all models tend to use the same wiring harness, although not all features are necessarily implemented in any one model. In using the same embryological blueprint for all birds, all birds will have wings.” ↩ ↩
3.
Schaller, Nina U. Structural attributes contributing to locomotor performance in the ostrich (Struthio camelus). Ruperto-Carola University of Heidelberg. 2008. A doctoral dissertation from the University of Heidelberg on how well the ostrich's body works for moving about (its locomotor performance). The author filmed and photographed four adult ostriches for signs of wing use and observed them in their enclosure over three years. Her wing section is 4.3.1, pp. 117–120. The article uses it as the only study it found that treats the ostrich wing as a running aid, and the author says her wing observations are not systematic data gathering.
1. 3a.
  Page 48: “By exploiting an extremity generally thought to be unnecessary in the locomotion of a flightless bird, the ostrich uses its relatively large wings as an 'air-rudder' by quickly extending them while running.” ↩ ↩
2. 3b.
  Page 117: “The wing skeleton is relatively long (~ 67 cm) when compared to other ratites, featuring a humerus as long as 43 cm with ulna and radius amounting to approximately one-third of humerus length (Bezuidenhout, 1999).” ↩ ↩
3. 3c.
  Page 117: “It must be understood that these observations are not the result of systematic data gathering but are rather intended to define obvious locomotor behaviours in which fore and hind limb activity appear inter-dependent.” ↩
4. 3d.
  Page 118: “Due to the stringent restrictions in hind limb mediolateral degrees of freedom, ostriches are largely unable to execute small radius turns at running speeds without the use of their wings”. ↩
5. 3e.
  Page 118: “an ostrich at speed can swiftly extend both wings to present a very large surface area to arrest forward motion by exerting maximum drag.” ↩
4.
Bertram, Brian C. R. The Ostrich Communal Nesting System. Princeton University Press, Princeton. 1992. A book on the ostrich's communal nesting system, published in 1992. The article uses it for what the wings do in an ostrich's life: temperature control, balance, protecting eggs and young, display, and whisking away flies.
1. 4a.
  Page 1: “Ostriches' wings are considerably reduced. The feathers are without barbs, which contributes to their loose, soft appearance. The primary feathers are developed as large plumes, used in display and sought after by human beings.” ↩
2. 4b.
  Page 7: “Ostriches are tolerant of high temperatures. They rarely seek shade, as most desert antelopes regularly do. Their feathers are excellent insulators, minimizing heat gain due to direct solar radiation, as well as reducing heat loss during cold desert nights. Temperature control is achieved by erecting and flattening the body feathers (Louw et al., 1969) and by panting at very high temperatures (Crawford and Schmidt-Nielsen, 1967).” ↩
3. 4c.
  Page 15: “The wings are used for a variety of display purposes in addition to their function in controlling the bird's temperature, in counterbalancing during fast manoeuvring, in protecting eggs and young, and in whisking away flies. Ostriches use a repertoire of visual displays fully described by Hurxthal (1979), and the wings play a major part in many of them.” ↩ ↩
4. 4d.
  Page 15: The kantling display. “While squatting, the male waves his quivering spread wings alternately in the air as he rocks from side to side.” ↩
5. 4e.
  Page 76: “Ostriches perform a distraction display which became more pronounced as incubation progressed. It is similar to the broken-wing display of many small ground-nesting birds, involving the ostrich scuttling away with wings low and flapping irregularly, and then collapsing on the ground.” ↩
5.
Farlie, Peter G. et al. “Co-option of the cardiac transcription factor Nkx2.5 during development of the emu wing.” Nature Communications 8:132. 2017. A laboratory study that compared emu embryos with ostrich, chicken and zebra finch embryos and found the heart gene Nkx2.5, which switches other genes on, active only in the emu's developing wing bud. Forcing the gene through the wing bud of chick embryos reduced wing growth and caused digit loss, but that test was done only in chickens, not emus. The article uses it for the emu's vestigial wing, which has a single digit.
1. 5a.
  Page 2: “The mature wing of the emu is vestigial, with no known function, and exhibits a substantially reduced and morphologically highly variable wing with an autopod harboring a single digit. In contrast, the ostrich and rhea possess functional wings with strongly reduced zeugopod and autopod harboring three digits.” ↩ ↩ ↩
2. 5b.
  Page 1, section Abstract: “Here we report a previously unknown co-option of the cardiac transcription factor Nkx2.5 to the forelimb in the emu embryo, but not in ostrich, or chicken and zebra finch, which have fully developed wings.” “We propose that Nkx2.5 functions to inhibit early limb bud expansion and later muscle growth during development of the vestigial emu wing.” ↩
6.
Parker, T. Jeffery. “Observations on the Anatomy and Development of Apteryx.” Philosophical Transactions of the Royal Society of London B 182:25–134. 1891. A long anatomy study of the kiwi, Apteryx, by a professor of biology at the University of Otago in New Zealand, covering its skeleton and wing muscles at several stages of growth. It found that the kiwi's wing still has a true alar membrane, the wing's skin flap, which Parker took as evidence that kiwis came from ancestors with well-developed wings. The article uses it for the kiwi's wing stub, which still has the two skin folds of a flying wing and a claw of 3 to 18 mm.
1. 6a.
  Page 36: “Another fact which appears to me to tell in favour of the derivation of Apteryx from a progenitor with well developed wings, is the fact that the wing is provided with a true alar membrane.” ↩
2. 6b.
  Page 36: “it has, precisely as in typical Carinatae, a distinct fold of skin, or pre-patagium, passing between the upper arm and fore arm, as well as an equally well marked fold, the post-patagium, between the postaxial border of the upper arm and the trunk.” ↩ ↩
3. 6c.
  Page 37: “As far as my experience goes, the alar claw of A. oweni is always soft and weak, gently curved, about 4 mm. long, and of a light horn colour”. “In A. australis it is about 6-8 mm. long, gently curved, and of a light horn colour, blotched with black”. “in A. bulleri, it is strongly curved, from 6 to 18 mm. long, and quite black”. For A. haastii: “the left claw of the supposed female specimen in the Canterbury Museum being only 3 mm. long”. “It seems to be constantly larger in the male than in the female, and often differs on the two sides of the body.” ↩ ↩
7.
Huynen, Leon et al. “Reconstruction and in vivo analysis of the extinct tbx5 gene from ancient wingless moa (Aves: Dinornithiformes).” BMC Evolutionary Biology 14:75. 2014. A laboratory study that rebuilt the gene tbx5 from ancient DNA of the giant moa and tested it in chicken embryos. Tbx5 is the gene that starts forelimb development, and the moa's version worked as well as the chicken's, so the authors conclude that other gene changes must explain why the moa lost its wing. The article uses it for the moa, which has no wing except a finger-sized shoulder bone, and for the finding that the moa's gene still worked.
1. 7a.
  Section Abstract: “Amongst birds, a single order, Dinornithiformes, comprising the extinct wingless moa of New Zealand, are unique in having no skeletal evidence of forelimb-like structures.” ↩
2. 7b.
  Section Background: “The only evidence that moa once had wings is the presence of a small finger-sized bone, the scapulocoracoid, a fused remnant of the forelimb girdle's coracoid and scapula”. ↩ ↩
3. 7c.
  Section Abstract: “Moa Tbx5 is identical to chicken Tbx5 in being able to activate the downstream promotors of fgf10 and ANF.” ↩
4. 7d.
  Section Abstract, conclusions: “Our results further show that genetic changes affecting genes other than tbx5 must be responsible for the”. The sentence goes on, outside the quotation marks: loss of the moa wing. ↩
8.
Burga, Alejandro et al. “A genetic signature of the evolution of loss of flight in the Galapagos cormorant.” Science 356(6341):eaal3345. Jun 2, 2017. A genetics study that sequenced the genomes of the flightless Galapagos cormorant and three flying cormorant species, then looked for gene variants that, in humans and mice, cause skeletal ciliopathies (diseases of cilia, the tiny hair-like parts of cells) and bone growth defects. It found a 12-base-pair deletion in the gene Cux1 that is fixed in the flightless population and missing from the flying species, and the authors call it a strong candidate to contribute to loss of flight. The article uses it for the cormorant's short wings and for its genetic route to flightlessness. Mirror: PMC
1. 8a.
  Section Introduction: “P. harrisi has a pair of short wings, which are smaller than those of any other cormorant (Fig. 1A); a deviation from the allometric relationship between wing length and body mass (7). The radius and ulna are disproportionally small compared to the humerus, but no digits have been fused or lost, unlike in some ratites (8).” ↩
2. 8b.
  Section Introduction: “shortened remiges (flight feathers), underdeveloped pectoral muscles, a long and narrow skull and pelvis, a disproportionally long tibiotarsus, a 1.6-fold increase in body mass, and a highly reduced keel (7).” ↩
3. 8c.
  Figure 1A: From the figure caption. “The average wing length of an adult Galapagos cormorant male is 19 cm (3.6 kg. body mass), whereas the wing length of its closest relative, the double-crested cormorant, is 31.5 cm. (2.2 kg. body mass).” ↩ ↩
4. 8d.
  Section Introduction: “In contrast to ratites and penguins, which became flightless over 50 million years ago (MYA) (5, 11), the Galapagos cormorant and its flighted relatives are estimated to share a common ancestor ~2 MYA (12).” ↩ ↩
5. 8e.
  Section Enrichment for genes mutated in skeletal ciliopathies: “Sanger sequencing of 20 Galapagos cormorant individuals from two different populations (Cabo Hammond and Cañones Sur) (57) revealed only homozygous carriers for all of the variants in Table 1, indicating that these variants are most likely fixed in the Galapagos Cormorant. In summary, we found an overrepresentation of predicted function-altering variants in genes that, when mutated in humans and mice, cause skeletal ciliopathies and bone growth defects.” ↩ ↩
6. 8f.
  Section CUX1 is mutated in P. harrisi: “We Sanger-sequenced and confirmed the predicted Cux1 12 base pair (bp) deletion in P. harrisi. We also confirmed that this variant is fixed in the population and absent in the other cormorant species (fig. S10A). The 12 bp deletion in Cux1 removes four amino acids, AGSQ, immediately adjacent to the C-terminal end of the homeodomain”. ↩ ↩
7. 8g.
  Section Discussion: “Diverse myological, osteological, and developmental observations suggest that flightlessness in the Galapagos cormorant is caused by the retention into adulthood of juvenile characteristics affecting pectoral and forelimb development (a class of heterochrony known as paedomorphosis) (7).” ↩
8. 8h.
  Section CUX1 is mutated in P. harrisi: “A function-altering variant in CUX1 is a strong candidate to contribute to loss of flight in P. harrisi because adenovirus-mediated overexpression in the developing chicken wing of a form of CUX1 missing the Cut2 DNA binding domain results in severe wing truncation”. Section CR3HD-CUX1 promotes chondrogenesis: “These results suggest that the Galapagos cormorant CUX1 is probably not as effective as the ortholog from its flighted relatives in promoting chondrogenic differentiation”. ↩
9.
Livezey, Bradley C. “Flightlessness in the Galápagos cormorant (Compsohalieus [Nannopterum] harrisi): heterochrony, giantism and specialization.” Zoological Journal of the Linnean Society 105(2):155–224. 1992. An anatomy study of the Galapagos cormorant's study skins, skeletons and dissected muscles, compared with eight flighted relatives. It found wings of 190 mm in males and 170 mm in females, the shortest of any cormorant, with flight feathers about 50% shorter, and a wing loading (body mass per unit of wing area) estimated at 5.1 against 1.0 to 1.7 for the flighted cormorants, using approximate wing areas. The article uses it for the wing reduction, measured against flying cormorants.
1. 9a.
  Section Abstract: “Wing lengths of C. harrisi were smaller than those of any other cormorant, averaging 190 mm and 170 mm for males and females, respectively. Wing-loadings (g body mass.cm−2 wing area) of flighted cormorants ranged from 1.0 to 1.7. Estimated wing-loadings, incorporating approximate wing areas, were 2.0 and 5.1 g.cm−2 for C. perspicillatus and C. harrisi, respectively”. ↩
2. 9b.
  Section Abstract: “The small wings of C. harrisi result from an c. 50% shortening of remiges, accompanied by reduced asymmetry of vane widths and increased rounding of the tips, and significant reductions in lengths of wing bones, particularly the radius and ulna. Numbers of primary and secondary remiges in C. harrisi remain unchanged.” ↩ ↩
3. 9c.
  Section Abstract: “No muscles or parts thereof were lacking in the pectoral limb of C. harrisi, but a number of qualitative differences distinguished the musculature of the flightless species”. ↩ ↩
10.
Coyne, Jerry A. Why Evolution Is True. Viking, New York. 2009. A 2009 book by Jerry A. Coyne that makes the case for evolution, as its title says. The article quotes it for the claim that flightless wings are nonfunctional, which the article rejects, and for Coyne's own statements that the ostrich wing has new uses and that flightless birds descend from flying ancestors.
1. 10a.
  Page 57: “The wings of the ostrich are a vestigial trait: a feature of a species that was an adaptation in its ancestors, but that has either lost its usefulness completely or, as in the ostrich, has been co-opted for new uses. Like all flightless birds, ostriches are descended from flying ancestors. We know this from both fossil evidence and from the pattern of ancestry that flightless birds carry in their DNA.” The paragraph ends: “They help the bird maintain balance, mate, and threaten its enemies.” ↩ ↩
2. 10b.
  Page 58: “Yet they all have exactly the same bones that we see in the wings of species that can fly. That's because the wings of flightless birds weren't the product of deliberate design (why would a creator use exactly the same bones in flying and flightless wings, including the wings of swimming penguins?), but of evolution from flying ancestors.” ↩
3. 10c.
  Page 59: “So why haven't they disappeared completely? In some cases they nearly have: the wings of the kiwi are functionless nubs. But when the wings have assumed new uses, as in the ostrich, they will be maintained by natural selection, though in a form that doesn't allow flight.” ↩
4. 10d.
  Page 64: “Tiny, nonfunctional wings, a dangerous appendix, eyes that can't see, and silly ear muscles simply don't make sense if you think that species were specially created.” ↩
11.
Gill, B. J. “Wing areas and wing loadings of New Zealand land birds.” Notornis 70(2):74–82. 2023. A measurement study by a former museum curator, who traced and measured the wings of 84 birds of 27 New Zealand land bird species and divided each bird's body mass by its wing area to get its wing loading. It found the lowest loading in the fantail (0.12 g/cm2) and the highest among flying birds in the pukeko (0.88 g/cm2), and the three flightless birds at 1.19 (weka), 1.62 (kakapo) and 2.98 (South Island takahe); the author says the samples are small and that high wing loading is an important sign of flightlessness but not the only factor. The article uses the takahe's figure against Meunier's flight limit of 2.5.
1. 11a.
  Page 78: “The weka is flightless at a wing loading of 1.19 g/cm2, the kakapo at 1.62 g/cm2 and the South Island takahe at 2.98 g/cm2 (Table 1).” ↩ ↩
2. 11b.
  Page 79: “Meunier (1951) gave a wing loading of 2.5 g/cm2 as a threoretical maximum that still permits flight.” "threoretical" sic. ↩ ↩
3. 11c.
  Page 79: “However, the highest wing loadings for Northern Hemisphere flying birds listed by Bird (1999: 249) are 1.56 g/cm2 for great bustard (Otis tarda), 1.70 for mute swan (Cygnus olor), 1.76 for whooper swan (C. cygnus), 1.79 for great northern diver (Gavia immer) and 2.01 for Canada goose.” ↩
12.
Harshman, John et al. “Phylogenomic evidence for multiple losses of flight in ratite birds.” PNAS 105(36):13462–13467. Sep 9, 2008. A DNA study that built a family tree of the ratites and their flying relatives, the tinamous, from 20 widely spread stretches of nuclear DNA, which is the genetic material in a cell's nucleus. It found that the tinamous sit inside the ratite group, so the ratites do not form one family line, and the authors conclude that flight was lost at least three times. The article uses this to show that flight was lost more than once among the ratites.
1. 12a.
  Page 13462, section Abstract: “The prevailing view is that ratites are monophyletic, with the flighted tinamous as their sister group, suggesting a single loss of flight in the common ancestry of ratites. However, phylogenetic analyses of 20 unlinked nuclear genes reveal a genome-wide signal that unequivocally places tinamous within ratites, making ratites polyphyletic and suggesting multiple losses of flight.” ↩
2. 12b.
  Page 13462, section Abstract: “The most plausible hypothesis requires at least three losses of flight”. ↩ ↩
13.
Mitchell, Kieren J. et al. “Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution.” Science 344(6186):898–900. May 23, 2014. A study of ancient DNA that sequenced the mitochondrial genomes, the small circles of DNA outside the cell nucleus, of two extinct Madagascan elephant birds. It found that the elephant birds are the closest relatives of the kiwi and not of the ostrich, which the authors say contradicts the older view that the ratites split apart as the supercontinent Gondwana broke up, and supports dispersal by flying ancestors in all the major ratite lines. The article uses it for the claim that each major ratite group lost flight separately.
1. 13a.
  Page 898: “By rendering ratites paraphyletic, the relationship between the moa and tinamous also strongly suggests that gigantism and flightlessness have evolved multiple times among palaeognaths (12, 13).” ↩
2. 13b.
  Page 899: “imply that every major ratite lineage independently lost flight (Fig. 1). We suggest that flighted dispersal was the primary driver of the distribution of palaeognath lineages”. ↩ ↩
14.
Eggleton, Michael. “The ostrich, a reminder of creation and the Fall.” Creation 41(4):28–31. Oct 2019. A popular article, not a study, in Creation, the magazine of Creation Ministries International, a young-earth ministry. It reports that many creationist biologists think most flightless birds had flying ancestors, and that genetic analysis now suggests flightlessness arose several times among the ratites. The article uses it as CMI's own statement on the ostrich's ancestry; the online copy is dated 26 October 2020.
1. 14a.
  “Many creationist biologists think that most flightless birds, if not all, had flying ancestors”. “And in this, they are in general agreement with evolutionists.” ↩
2. 14b.
  “For one thing, the huge moas of New Zealand, wiped out by indigenous overhunting, seem most closely related to the tinamous, small birds that can fly. So, it is now thought that flightlessness arose independently in the ratites multiple times.” ↩
3. 14c.
  “It's actually very easy for creatures to lose complex abilities such as flight.” ↩
4. 14d.
  “So, when a genetic accident (mutation) cripples some part of the complex flight machinery, the flightless form, which would normally be eliminated as defective, is very likely to dominate the island population.” ↩
5. 14e.
  Section Evolution, ratites, and created kinds: “Hybridization studies, not yet available, could help to determine how many created kinds are within the ratites, and thus how many times flightlessness arose.” ↩
6. 14f.
  Section Evolution, ratites, and created kinds: The quoted "He" is Jon Ahlquist, the late expert on bird genome trees, who became a biblical creationist. “He thought that the genetic data was most consistent with ratites and tinamous having descended from one ancestral (flying) population that came off the Ark. Other creationist researchers think ratites likely represent more than one kind, each originally flying.” ↩
15.
Sackton, Timothy B. et al. “Convergent regulatory evolution and loss of flight in paleognathous birds.” Science 364(6435):74–78. Apr 5, 2019. A genome study of 11 newly sequenced paleognath genomes, the group that holds the flightless ratites and the flying tinamous, including an extinct moa. It scanned 284,001 stretches of noncoding DNA, which are regions that control genes rather than code for proteins, and found 2,355 that changed unusually fast along the flightless lines. The authors conclude that the same control regions changed independently each time a lineage lost flight, more than the protein-coding genes did, and the article uses this to show that the change happened in regulation as well as in genes.
1. 15a.
  Section Abstract: “We combined phylogenomic, developmental, and epigenomic analysis of 11 new genomes of paleognathous birds, including an extinct moa, to show that convergent evolution of regulatory regions, more so than protein-coding genes, is prevalent among developmental pathways associated with independent losses of flight. A Bayesian analysis of 284,001 conserved noncoding elements, 60,665 of which are corroborated as enhancers by open chromatin states during development, identified 2355 independent accelerations along lineages of flightless paleognaths, with functional consequences for driving gene expression in the developing forelimb.” ↩ ↩
16.
van de Crommenacker, Janske et al. “Rapid loss of flight in the Aldabra white-throated rail.” PLoS ONE 14(12):e0226064. Dec 23, 2019. A genetic and body-measurement study of the Aldabra white-throated rail, a flightless bird on Aldabra in the Seychelles that is only a subspecies, a named population within one species, of a rail whose other populations fly. The authors used DNA from modern birds and museum specimens and estimate that the rail lost flight within at most 80,000 to 130,000 years, which they class among the most rapid documented losses of flight. The article uses that figure as its measured case of fast flight loss.
1. 16a.
  Page 1, section Abstract: “Our data places D. [c.] aldabranus among the most rapid documented avian flight loss cases (within an estimated maximum of 80,000–130,000 years).” ↩ ↩
17.
Hume, Julian P., and David Martill. “Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra.” Zoological Journal of the Linnean Society 186(3):666–672. Jul 2019. A fossil study of Dryolimnas rails on Aldabra, an atoll in the Seychelles. It found flightless rail fossils in two deposits, one from before and one from after a high sea level that flooded the atoll and wiped out its land animals, and the authors conclude that a rail reached the atoll, most likely from Madagascar, and became flightless separately on each occasion. The article uses this for the claim that flight was lost twice on one atoll.
1. 17a.
  Section Abstract: “A flightless Dryolimnas has been identified from two temporally separated Aldabran fossil localities, deposited before and after the inundation event, providing irrefutable evidence that a member of Rallidae colonized the atoll, most likely from Madagascar, and became flightless independently on each occasion.” ↩ ↩
18.
Fulton, Tara L. et al. “Multiple losses of flight and recent speciation in steamer ducks.” Proceedings of the Royal Society B 279(1737):2339–2346. 2012. A DNA study of the steamer ducks of South America and the Falklands, using more than 50 birds from living birds and historic specimens. It found that the flying and flightless ducks on the Falklands are genetically indistinguishable, and the authors say the family tree fits several losses of flight or a long period of partial flight. The article uses it as an example of a gradient from full flight to none inside one genus.
1. 18a.
  Section Abstract: “Steamer ducks (Tachyeres) comprise four species, three of which are flightless.” ↩
2. 18b.
  Section Abstract: “the flying and flightless steamer ducks on the Falkland Islands are genetically indistinguishable, in contrast to their traditional classification as separate species.” ↩ ↩
3. 18c.
  Section Abstract: “The three continental species share a common ancestor approximately 15 000 years ago, possibly owing to isolation during a recent glacial advance.” ↩
4. 18d.
  Section Abstract: “Each lineage of Tachyeres represents a different stage between flight and flightlessness.” ↩
19.
Arledge, Scott. “Flightless by Design or Designed by Death?” Institute for Creation Research. Feb 28, 2022. A question-and-answer article by Scott Arledge, research coordinator at the Institute for Creation Research, a young-earth ministry. It argues from the white-throated rail that its flightlessness was designed, not caused by a mutation. The article uses it as the outlier creationist reply: it denies the mutation account, yet still grants that the rail's wings and muscles are reduced.
1. 19a.
  “Many believe this bird didn't become flightless by design. They surmise instead that a random genetic mistake disabled it”. “Unfortunately, creationists sometimes come along and repeat this make-believe story.” ↩
2. 19b.
  “Their heavy breast muscles used for flight can consume 32% of total daily energy used, so they're reduced in size. Their wings and related muscles are also reduced.” ↩
3. 19c.
  “Flightlessness is not a mutation, and it's certainly not designed by wind.” ↩ ↩
4. 19d.
  “Rails are engineered to be flightless if needed so they can thrive on a faraway tiny island and thereby fill the earth just like Jesus designed them to do.” ↩
20.
Society for Experimental Biology. “Feathered friends: Ostriches provide clues to dinosaur movement.” EurekAlert! Jun 30, 2010. A press release from the Society for Experimental Biology, issued 30 June 2010 for Nina Schaller's talk at the society's annual conference in Prague. The article uses it only for Schaller's comparison of the ratites: rheas use their wings for balance, while the emu and cassowary do not use theirs in locomotion.
1. 20a.
  Nina Schaller, the lead researcher, as quoted in the release. “'South American rheas execute rapid zigzagging as a means of escape and use their wings to maintain balance during these agile manoeuvres', she explained.” ↩
2. 20b.
  Nina Schaller again, as quoted in the release. “However, other relatives such as the Australian emu and the Cassowary have very small wings which they hold very tightly to their body and are not used in locomotion. 'There seems to be a very direct link between wing-size and function', she added.” ↩
21.
Livezey, Bradley C. “Morphological corollaries and ecological implications of flightlessness in the kakapo (Psittaciformes: Strigops habroptilus).” Journal of Morphology 213(1):105–145. 1992. An anatomy study of the flightless kakapo, a New Zealand parrot, using its skin specimens, skeletons and the dissected pectoral muscles of one specimen, compared with the flighted kea and other parrots. It found that the kakapo has the smallest relative wing size of any parrot, a vestigial carina (the keel on the breastbone, which anchors the flight muscles) and greatly reduced chest flight muscles. The article uses it for the kakapo's small wing and reduced flight muscles.
1. 21a.
  Section Abstract: “S. habroptilus is the most massive and sexually dimorphic psittaciform in the world, and has the smallest relative wing size of any parrot.” ↩
2. 21b.
  Section Abstract: “S. habroptilus shows peculiarities of the sternum (vestigial carina, shortened spina externa)”. “Distinctive features of the pectoral musculature of S. habroptilus include a greatly reduced Mm. pectoralis thoracica and supracoracoideus”. ↩
22.
Darwin, Charles. On the Origin of Species by Means of Natural Selection. John Murray, London. First edition. 1859. Charles Darwin's book setting out evolution by natural selection, in its first edition. The article uses three things Darwin wrote in it: that disuse left some island birds nearly wingless, that the ostrich's wings shrank as its body grew, and that rudimentary organs (body parts reduced to a small or partly formed state) vary a great deal between individuals.
1. 22a.
  Page 134: “As Professor Owen has remarked, there is no greater anomaly in nature than a bird that cannot fly; yet there are several in this state. The logger-headed duck of South America can only flap along the surface of the water, and has its wings in nearly the same condition as the domestic Aylesbury duck. As the larger ground-feeding birds seldom take flight except to escape danger, I believe that the nearly wingless condition of several birds, which now inhabit or have lately inhabited several oceanic islands, tenanted by no beast of prey, has been caused by disuse.” ↩ ↩
2. 22b.
  Pages 134–135: “The ostrich indeed inhabits continents and is exposed to danger from which it cannot escape by flight, but by kicking it can defend itself from enemies, as well as any of the smaller quadrupeds. We may imagine that the early progenitor of the ostrich had habits like those of a bustard, and that as natural selection increased in successive generations the size and weight of its body, its legs were used more, and its wings less, until they became incapable of flight.” ↩
3. 22c.
  Page 452: “Rudimentary organs in the individuals of the same species are very liable to vary in degree of development and in other respects.” ↩
23.
Elliott, Kyle H. et al. “High flight costs, but low dive costs, in auks support the biomechanical hypothesis for flightlessness in penguins.” PNAS 110(23):9380–9384. 2013. A field study that measured the energy cost of flight and of diving in two free-living seabirds that both fly and dive, the thick-billed murre and the pelagic cormorant. It found that flight costs in these birds are the highest recorded for vertebrates, and the authors say this supports the idea that a wing built for diving becomes too costly to fly with. The article uses it to explain why penguins gave up flight, though the penguin figures come from earlier work and not from the murres and cormorants measured here.
1. 23a.
  Section Abstract: “We show that flight costs for thick-billed murres (Uria lomvia), which are wing-propelled divers, and pelagic cormorants (Phalacrocorax pelagicus) (foot-propelled divers), are the highest recorded for vertebrates.” ↩
2. 23b.
  Section Abstract: “optimizing wing shape and form for wing-propelled diving leads to such high flight costs that flying ceases to be an option in larger wing-propelled diving seabirds, including penguins.” ↩
24.
Wright, Natalie A. et al. “Predictable evolution toward flightlessness in volant island birds.” PNAS 113(17):4765–4770. Apr 26, 2016. A survey of island birds that weighed the flight muscles of more than 8,000 carcasses from 868 landbird species, then tracked 366 island populations from 80 islands in the Pacific and Caribbean. It found smaller flight muscles and longer legs on islands, with the shift strongest where few predators live, and the authors say most of these populations stay able to fly. The article uses it to show that the reduction of flight muscles starts well before flight is lost.
1. 24a.
  Page 4765, section Abstract: “We found that island bird species have evolved smaller flight muscles than their continental relatives. Furthermore, in 366 populations of Caribbean and Pacific birds, smaller flight muscles and longer legs evolved in response to increasing insularity and, strikingly, the scarcity of avian and mammalian predators.” ↩
2. 24b.
  Page 4765: “Transitions to flightlessness are rapid and irreversible”. “More than 1,000 independent lineages of island birds have lost flight, including rails, parrots, pigeons, owls, waterfowl, and passerines”. ↩ ↩
25.
Cloutier, Alison et al. “Whole-Genome Analyses Resolve the Phylogeny of Flightless Birds (Palaeognathae) in the Presence of an Empirical Anomaly Zone.” Systematic Biology 68(6):937–955. 2019. A family-tree study of the palaeognaths, the ratites and tinamous, built from 20,850 stretches of noncoding nuclear DNA in 14 species. It places the rheas as the sister group of the kiwi and the emu and cassowary together, and says that short branches between these lineages make the tree hard to resolve. The article uses it for the point that recent molecular studies agree the ratites do not form a single group.
1. 25a.
  Section Introduction: “Although ratite paraphyly is strongly supported by all recent molecular studies (Hackett et al. 2008; Harshman et al. 2008; Phillips et al. 2010; Haddrath and Baker 2012; Smith et al. 2013; Baker et al. 2014; Mitchell et al. 2014; Grealy et al. 2017; Reddy et al. 2017; Yonezawa et al. 2017), rheas have been variously placed”. ↩
26.
Cosner, Lita, and Jonathan Sarfati. “The birds of the Galápagos.” Creation 31(3):28–31. Jun 2009. A popular article, not a study, in Creation, the magazine of Creation Ministries International, about the birds of the Galápagos Islands. It says that without flight the flightless cormorant's wings have deteriorated, and that the loss came through a mutation that removed genetic information. The article uses it as the creationist authors' own account that the cormorant lost flight by mutation; the online copy is dated 2 August 2010.
1. 26a.
  Section Flightless cormorants: “The changes that the flightless cormorant underwent are similar to that of other flightless birds; the keel on the breast bone which supports the muscles used for flight is much smaller, and its legs are much stronger than those of other cormorants. Not needing to use its wings for flight, its wings have deteriorated in ways that would have been eliminated in flying birds.” ↩
2. 26b.
  Section Flightless cormorants: “Darwin proposed that it developed from cormorants that had flown to the island, but whose descendants had lost this ability. Now we realize that this loss occurred through a mutation, or genetic copying mistake.” ↩
27.
Answers in Genesis. “The Bird That Fishes, But Doesn't Fly.” answersingenesis.org. May 24, 2005. A short popular web article from Answers in Genesis, a young-earth ministry. No individual author is named on the page. It takes the flightless cormorant of the Galápagos Islands as its example, and the article uses it for the ministry's answer that the cormorant's ancestors could fly.
1. 27a.
  “So how did cormorants first arrive here? The most likely answer is that its ancestors could fly. In a fallen world, the loss of the ability to fly through mutational degeneration would be a disadvantage in the struggle to survive.” ↩
28.
Cserhati, Matthew. “Rails derail evolution.” Creation Ministries International. Jun 18, 2019. A reply article from Creation Ministries International, a young-earth ministry, updated on 8 August 2019. It answers a 2019 paper by Hume and Martill that found flight lost several times in the white-throated rail on islands near Madagascar, and it argues that losing a structure is not evolution. The article uses it because it concedes that flight was lost several times and that the loss was rapid.
1. 28a.
  Section Loss of flight is not evolution!: “Flightlessness is not a characteristic that can be gained, since it involves the loss of a morphological structure (for example, consider the flightless cormorants that Charles Darwin saw on the Galápagos Islands). No new gene arose for the development of any new kind of structure.” ↩
2. 28b.
  Section Loss of flight is not evolution!: “It is quite possible that these birds actually lost genetic information (i.e. one or more mutations in homeobox genes, which function in development) or in some other piece of coding DNA for flight structures.” ↩
3. 28c.
  Section Loss of flight is not evolution!: “This would be a case of devolution and not evolution. The actual de novo generation of genes responsible for flight has never been demonstrated.” ↩
4. 28d.
  Section Loss of flight is not evolution!: “The probability of the same organ being affected on different occasions over tens to hundreds of thousands of years in the same species is very small indeed.” ↩
5. 28e.
  “Loss of flight has also happened in several other bird species, such as the great auk, the dodo, the moa, ostrich, rhea, emu, cassowary, kiwi and kakapo.” ↩
6. 28f.
  Section Loss of flight is not evolution!: “Lastly, the rapidity of flight loss in these birds goes against the standard evolutionary view of millions of years being required for such processes to happen.” ↩
29.
O'Daniel, Donna. “Flightless Birds: Alternate Flight Plan.” Answers magazine. Jan 1, 2015. A magazine feature, printed in the January-March 2015 issue of Answers magazine, by Donna O'Daniel, who holds an MA in biological sciences and has worked as a wildlife biologist. It surveys the flightless birds by group and counts 38 species and island subspecies of flightless land birds and 26 flightless waterbirds alive today. The article uses it because it admits that creationists disagree over whether some kinds of birds ever flew, and because it gives the keel evidence for loss of flight.
1. 29a.
  “At present, however, there is no consensus among creationists whether some kinds of birds never flew. Some believe that all birds were initially created with the ability to fly. Supporting this belief is the fact that the keels of several species seem to be in different stages of deterioration, thus possibly indicating the progressive loss of flight. For instance, the keel of the flightless cormorant is much smaller than those of other cormorants, the sternum of the kakapo (Strigops habroptilus, a flightless parrot of New Zealand) is now just a low ridge, and the ratite sternum is completely flat, with no semblance of a keel.” ↩
2. 29b.
  “Other creationists believe, however, that certain bird kinds were created by God to be flightless. Their unique and integrated designs, especially ratites and penguins, point to God's special design, not accidents and loss.” ↩
30.
Maloney, Shane K. “Thermoregulation in ratites: a review.” Australian Journal of Experimental Agriculture 48(10):1293–1301. 2008. A review of how ratites (flightless birds such as the emu, ostrich and kiwi) keep their body temperature, drawing on laboratory and free-ranging studies of those birds. The article uses it because its abstract credits insulation, metabolic heat and evaporative water loss, and does not mention the wings.
1. 30a.
  Section Abstract: “While body temperature and basal metabolic rate are lower in ratites than other birds, all of the thermoregulatory adaptations present in other birds are well established in ratites.” “Below that zone, homeothermy is achieved via the efficient use of insulation and elevated metabolic heat production. In the heat, emus and ostriches increase respiratory evaporative water loss and use some cutaneous water loss.” ↩