Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education ARCHAEOPTERYX ple of how fossils are important for showing transitional features of evolution, and how the ARCHAEOPTERYX: THE FOSSIL fossil record is good evidence that evolution ontrary to Wells’s subtitle, has occurred. Archaeopteryx is not a “missing link.” WELLS MISSES MORE CThe term “missing link” is an outdated THAN THE LINKS term that does not accurately reflect the way ells objects to textbook treatments biologists and paleontologists think about fos- of Archaeopteryx as a transitional sils. We prefer not to talk about “missing Wform or as an “ancestor” of birds. links” or “intermediate forms,” but rather Wells wants textbooks to say that intermediate features. Archaeopteryx has fea- Archaeopteryx was not an “ancestor” because tures intermediate between those of living modern birds are not descended from it and birds and ancient reptiles; along with many that its transitional status is “controversial.” other fossils, it preserves ancestral features Wells claims that Archaeopteryx has been while it shows descendant novelties. “quietly shelved” by paleontologists and that Archaeopteryx retains the ancestral “reptilian” the search for a “missing link” between features of a long bony tail, clawed hands, dinosaurs and birds goes hopelessly on “as teeth, and many others. It also has the derived though Archaeopteryx had never been found” “avian” features of feathers and powered (Wells, 2000:138). Paleontologists would find flight. Archaeopteryx, along with other this surprising. By making such claims, Wells dinosaur fossils, shows the evolution of avian exposes the depths of his ignorance of phylo- features and flight. These fossils show that genetic methodology, paleontology, and avian many features thought of as unique to a certain evolution. group of animals were also shared by some of Wells is clearly confused by Archaeopteryx, their ancestors; this helps paleontologists to “transitional forms,” and ancestors. First of all, reconstruct the evolutionary history of living Wells asserts that Archaeopteryx is no longer animals. When many fossils are looked at in considered a transitional form or an “ances- their genealogical context, they blur the lines tor.” Wells is correct, but only in a specialized between the normally recognized taxonomic sense, not appropriate in the context of his groups (most of which were based originally generalized discussion. We cannot — and do only on living forms). Archaeopteryx is fre- not — say for certain that the animal that we quently used for pedagogical purposes because call Archaeopteryx was actually genetically it is easy to recognize its mixture of “bird” and transitional to living birds, or that it was a “reptile” features and because it played an his- direct genetic ancestor of living birds. torical role in helping to cement Darwin’s the- However, in a less strict sense (that appropriate ory (it was discovered 2 years after publication to Wells’s discussion), Archaeopteryx has a of the Origin). Textbook authors like great many transitional features between living Archaeopteryx for these reasons and often birds and Mesozoic dinosaurs: if it was not a illustrate their discussions with pictures of the direct ancestor, it was surely a close collateral Berlin specimen, one of the most beautiful fos- ancestor (see below). sils ever discovered, and remarkably complete. Second, there is no such thing as a “missing Textbooks also use Archaeopteryx as an exam- link,” and paleontologists are not looking for 41 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education them. Paleontologists collect, survey, and rect. Archaeopteryx has no features that would reconstruct past forms of life. Some of these actually disbar it from being a direct ancestor fossil organisms have features that illustrate of living birds. Whether it was a direct ances- the path evolution took to reach the forms we tor of today’s birds or not is irrelevant: see today. We can think of these organisms as Archaeopteryx exhibits unique features of the showing transitional or ancestral features. last ancestor it shared with birds, so, regardless Paleontologists are also not looking for ances- whether it is a lineal ancestor, it still preserves tors, but rather features of ancestors. features that indicate what the last ancestor of Paleontologists distinguish between lineal and Archaeopteryx and birds may have been like. collateral ancestors. Lineal ancestors are those In other words, Archaeopteryx has many fea- that are directly ancestral to living organisms: tures intermediate between those of its your lineal ancestors are your father and moth- dinosaurian ancestors and its avian descen- er, grandfathers and grandmothers, and so on. dants, which is exactly what would be predict- Collateral ancestors are those organisms that ed by evolution. No amount of stridency on share an ancestor with living organisms: your Wells’s part can change that. collateral ancestors are your uncles, great- When paleontologists reconstruct relation- uncles, cousins, second cousins, and so on. ships of living and fossil organisms, they use Paleontologists do not claim to be able to iden- the features of both living and fossil organ- tify lineal ancestors. Without observational or isms. This allows them to reconstruct the fea- genetic evidence, how could you ever know tures of the ancestors and get a pretty good pic- that a fossil organism left any offspring? It is ture of what the ancestors were like. not the ancestry that is important to paleontol- Phylogenetic systematics, commonly called ogists, but rather the ability to reconstruct the “cladistics,” is the method that nearly all biol- features of those ancestors. This is a powerful ogists use to determine relationships, whether and important concept, one completely lost on they work on dinosaurs or dinoflagellates, and Wells. whether they use molecules or morphology. Its To illustrate this powerful approach, let’s simplicity, objectivity, testability, repeatability, say you wanted to know something about your utility, and firm rooting in the principle of own ancestors. If you knew your ancestors descent has led to its near-universal applica- came from a certain small village in France in tion. Contrary to Wells’s characterization, the 1600s, you could return to that village and, cladistics is not a search for “missing links” or even if you can’t locate their graves, you might direct ancestors, but for shared evolutionary find those of many of their contemporaries in features. The basic idea behind cladistics is the churchyard. A collection of artifacts from that when novel features arise, they are passed any of those people would give you a perfect- on to descendents. Therefore, these “derived ly adequate idea of the characteristics, culture, features” should be more informative in recon- possessions, and daily life of your direct structing relationships than those that are pres- ancestors (Padian and Angielczyk, 1999). ent across a larger group. For example, if a Using similar methods for similar reasons, population of animals evolve stripes on their paleontologists try to uncover features of backs and all their descendants continue to ancestors, not the ancestors themselves. sport stripes, then all the members of that Even Wells’s claim that paleontologists do species that have stripes are probably more not think Archaeopteryx is “ancestral” is incor- closely related to each other than they are to 42 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education those without stripes. It is that simple, yet ing” the evidence, stating that the supposed Wells’s discussion of cladistics reveals that he “ancestors” of Archaeopteryx are millions of either does not grasp the method or has no years younger. First of all, none of these more interest in explaining it properly. “recent” avian-like dinosaurs thought to be In the nearly two pages devoted by Wells to closely related to Archaeopteryx (e.g., a discussion of cladistics (Wells, 2000:118– troodontids and dromaeosaurs) are considered 119), he states that cladistics is based on over- “ancestors”; rather, they retain ancestral fea- all similarity. Yet as stated above, cladistics is tures that show us what the ancestors of not based on mere similarity, but instead Archaeopteryx were like. Here again Wells focuses on a special kind of similarity — fea- mistakes lineal for collateral ancestry. Second, tures that are derived, or evolutionary novel- the statement that there are no fossils of these ties. Evolutionary novelties help to show rela- close cousins of Archaeopteryx until “millions tionships and thus are “phylogenetically of years” later is false. Fossils of non-avian informative.” In contrast, similarities that are maniraptor dinosaurs, which are closely relat- not evolutionary novelties are “ancestral” fea- ed to the ancestors of Archaeopteryx, have tures and are not phylogenetically informative. been found in rocks dating to the same age as For example, a derived feature of primates is those in which Archaeopteryx has been found an opposable thumb; this feature is phyloge- (Jensen and Padian, 1989); this discovery was netically informative because it allows us to reported over 10 years ago. Wells apparently group all primates together to the exclusion of has not done his homework very well. other mammals. On the other hand, a five-fin- Despite Wells’s claims to the contrary, gered hand is an ancestral feature and not phy- Archaeopteryx is still an important contributor logenetically informative because we would to our knowledge of transitional features, and not group all animals possessing a five-fin- it clearly shows the dinosaurian ancestry of gered hand together to the exclusion of those birds (Figure 12). To confirm this, all one has that do not. For example, we do not propose to do is peruse any piece of literature on the that all five-fingered mammals are more close- origin of birds. Papers on Archaeopteryx and ly related to each other than they are to three- bird evolution appear in many journals each fingered, two-fingered, or one-fingered mam- year, and there is even an entire journal (called mals. So cladistics is not based on mere simi- Archaeopteryx) devoted to the study of larity. Further, paleontologists who apply Archaeopteryx and its environment. Rather cladistic methods to the problem of avian evo- than consult the vast body of literature on the lution do not think that how flight evolved is origin of birds, Wells appears to base much of “irrelevant”; in fact we specifically use clado- his discussion on two popular works, one tech- grams to inform our models of how flight (and nical — The Mistaken Extinction by Lowell other things) evolved. By rooting our explana- Dingus and Tim Rowe (1998) — and the sec- tions in phylogenies, we can move beyond ond non-technical — Taking Wing, by Pat subjective models, and constrain our hypothe- Shipman (1998). Both are excellent books. ses (e.g., Witmer, 1995; Padian, 1995). These However, during the same period when Wells explanations can also serve as yet another apparently wrote Icons (1998–1999), well over independent test of our phylogenies (Padian, 50 papers were published that in some way 2001a, 2001b). dealt with Archaeopteryx and the dinosaurian Wells then accuses cladistics of “rearrang- origin of birds. A number of these were very 43 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education
Figure 12. Archaeopteryx (bold) shown in evolutionary context with respect to crocodilians, non- avian dinosaurs, and birds. Some relevant features plotted. 44 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education important (e.g., Britt et al., 1998; Padian and well done and can fool an untrained eye, which Chiappe, 1998; Forster et al., 1998; Ji et al., is more or less what happened with 1998; Burgers and Chiappe 1999; Chiappe et “Archaeoraptor.” The first paleontologists to al. 1999; Clark et al., 1999; Garner et al., 1999; see the specimen were immediately suspicious Norell and Makovicky, 1999; Ostrom et al., because the prevalence of composite speci- 1999; Wagner and Gauthier, 1999; Xu et al., mens was already known, and its distribution 1999), yet Wells cites none of them. of features were not what would be expected in Wells also ignores the many fossil discover- an avian-like dinosaur. We would not expect it ies of feathered non-avian dinosaurs from to have the arms of a primitive bird and the Liaoning, China (see Figure 13), which should legs of a non-avian theropod. Even though a play an important role in any discussion of number of paleontologists were skeptical, avian origins, save for one notable exception. National Geographic went ahead with an arti- In an attempt to discredit the entire field, Wells cle that featured this specimen along with two brings up “Archaeoraptor,” which he regards others. This became an embarrassment for as a “hoax” and indicative of the sloppy sci- National Geographic when, at nearly the same ence that paleontologists do. In fact Wells time it ran its article, computerized axial spends the remaining third of the chapter try- tomography (CAT) scanning of the specimen ing to use “Archaeoraptor” in an attempt to showed it to be a composite. As it turns out, the slander the field of paleontology. Here too, he legs of the specimen belong to the counterslab gets most of the facts wrong. of a tiny non-avian theropod called “Archaeoraptor” was a fossil bought at the Microraptor (Xu et al., 2001); a full descrip- Tucson Gem and Mineral Show for Steve tion of the composite was published by Rowe Czerkas, a knowledgeable dinosaur enthusiast et al. (2001). To view the scans of the compos- and skilled sculptor and artist. Its remains ite, visit the UT Austin CT lab website came from the Liaoning area of China, which (www.ctlab.geo.utexas.edu/pubs/nature2000). has produced numerous beautifully preserved Wells concludes that this sorry episode fossils of fish, mammals, lizards, and both occurred because of “the cladists’ desire to avian and non-avian dinosaurs. Many of these prove their theory. Just as the need for a miss- were preserved with their body coverings, ing link between apes and humans led to such as fur or feathers, intact. So it was not Piltdown man, so the need for a missing link unexpected to see an allegedly new find from between dinosaurs and birds paved the way for there that combined features of fossil birds and the ‘Piltdown bird.’” (Wells, 2000:125). Not closely related dromaeosaurid dinosaurs, espe- so. The people who bought and promoted the cially given the large body of evidence sug- specimen weren’t cladists, and they never per- gesting that birds evolved from these formed a cladistic analysis or attempted to dinosaurs. The fossils of Liaoning are collect- place the specimen in a phylogeny. Piltdown ed by local villagers and farmers who know man was an intentional hoax played on scien- that “complete” specimens, particularly those tists, and the hoax was revealed by scientists with feathers, are preferred by scientists and when the specimen was studied. The forgery of collectors. Therefore, a cottage industry has “Archaeoraptor” was discovered by scientific sprung up around using parts to enhance or investigation as well, and it was cladists Tim make “whole” specimens (Chiappe et al., Rowe, Xu Xing, and Phil Currie who uncov- 1999). These constructed specimens are very ered it. The name “Archaeoraptor” was never 45 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education formally published as a scientific name, and tematists don’t use the term “fish” except in a has no scientific standing — the animal never restricted sense referring either to a subgroup existed. This doesn’t prevent Wells from itali- that is monophyletic such as Actinopterygia or cizing the name as if it were a real species. to “rayfins” (things like goldfish, trout, sword- Further, the specimen was never considered fish, etc.) — the vast majority of living “fish- important to our understanding of avian evolu- es.” Humans are vertebrates; so are fishes. tion. This doesn’t stop Wells from pretending Birds, by phylogenetic relationship, are otherwise, as if it were somehow important, dinosaurs. Just as dogs are canids, and also even crucial, to the idea that birds are descend- mammals, and also tetrapods and vertebrates. ed from dinosaurs. Consider a mailing address: just because you Returning to Archaeopteryx, Wells then live on 1010 Main Street does not mean that resorts to a classic creationist taxonomy game. you don’t live in Peoria or in Illinois, or that In this game, the creationist says that scientists someone living on 411 South Street doesn’t have to choose whether a fossil belongs to one live in the same town or state. taxonomic group or another. So, in the case of Wells’s most ridiculous treatment of “sci- Archaeopteryx, it has to be a bird or a reptile. ence” in this chapter is when he takes childish Then the creationist says that because it has shots at paleontologists. This is another popu- feathers it is a bird, and therefore because it is lar creationist tactic: attacking the character of a “bird” it cannot be a transitional form. In a prominent scientist or scientific field. In fact, effect the transitional features of the fossil are he devotes six pages to making fun of paleon- defined out of existence. This is a classic cre- tologists at a Florida symposium without ationist ploy, and nothing new; it is what we appearing to understand what they were say- have seen for decades from Duane Gish and ing. Worse yet, Wells completely misrepre- Henry Morris. Wells uses a slightly different sents the proceedings. For example, he claims approach, claiming that if Archaeopteryx and that a “cladistic analysis” showed a specimen birds are just dinosaurs, then humans are just presented there, called “Bambiraptor,” to be fish, which — he implies — is absurd. But this an ancestor of Archaeopteryx, yet no “cladistic is another case of Wells trying to use semantics analysis” was mentioned in either the descrip- to negate the evidence of evolution, just as he tion (Burnham et al., 2000) or the conference did with the Cambrian Explosion. proceedings. To my knowledge, no cladistic Here Wells exploits the systematic practice analysis has ever been performed on that spec- by which all groups of organisms must be imen. Wells then claims to be appalled that in “monophyletic,” that is, consist of an ancestor the reconstruction, “Bambiraptor” was shown and all of its descendants. In Wells’s rather covered in feathers even though none were naïve example, “fish” must be taken to include found fossilized with it. But other fossilized hagfishes, lampreys, sharks, goldfish and other dromaeosaurid dinosaurs are found covered in rayfins, coelocanths, and lungfishes. If “fish” feathers (e.g. Xu et al., 1999; Ji et al., 2001; were defined that way, then tetrapods (all ani- Norell et al., 2002) and so are the more basal mals that have four limbs) would indeed be Oviraptorids (Ji et al., 1998). The even more “fish” and “fish” would become another name basal Compsognathids are found with down- for “vertebrate.” But “fish” is not a taxonomic like feathers as well (Chen et al., 1998; see name; it is a colloquial term, and as a Ph.D. Figures 12, and 13). So it is conservative to biologist, Wells should know that. Real sys- reconstruct “Bambiraptor” with a covering of 46 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education
Figure 13. Some examples of feathered dinosaurs discovered in Laioning, China.
47 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education feathers. Besides, the reconstruction is a pic- has no training or expertise in the field. ture, not scientific evidence — a confusion of Instead, he relies on caricatures of paleontol- Wells’s revealed further in the peppered moths ogy and paleontologists, and lampoons the chapter. By Wells’s logic, we shouldn’t accept entire field, treating scientists as if they were a the likelihood of fur on a fossil sabertooth cat. bunch of dinosaur-loving buffoons who are Is this the kind of “critical thinking” Wells easily fooled and misled. This is not science or wants us to teach our students? scholarship; this is tabloid journalism. Finally, Wells charicatures the conference WHAT THE TEXTBOOKS SAY presentation of Kevin Padian, who not only is a respected paleontologist but also happens to extbooks cover Archaeopteryx with be the president of NCSE. Padian’s talk was a varying degrees of brevity, frequently critique of the hypothesis that birds evolved Tgiving only a paragraph to from something other than dinosaurs. Wells Archaeopteryx, usually in the section on rep- likens Padian’s talk to an “old lawyers’ joke” tiles or birds or in the history of life section. about a “cracked kettle.” Wells even says that The lengths of the paragraphs vary from 54 Padian was not trying to be funny, and that it words to well over 500 (Figure 14), and the would be unkind to compare his talk to the average length falls around 200 words. joke, yet he continues the ad hominem attack Archaeopteryx is frequently used as an exam- summarizing Padian’s talk as a joke. Wells’s ple of a transitional form between reptiles summary, however, looks nothing like either (dinosaurs) and birds. Eight of the books treat the abstract that Padian submitted, which it as showing a dinosaurian ancestry for birds, Wells (as a conference attendee) received, or while two state that the ancestry is simply rep- the text of the talk he gave. In particular, tilian (Figure 14). Few of these books treat Padian never called the critics of the dinosauri- Archaeopteryx well and most of these discus- an origin of birds “unscientific,” just their crit- sions are garbled and contain factual errors icisms. He never accused them of “selective about Archaeopteryx. For example, Guttman interpretation” of the evidence; he just said contains numerous errors, even suggesting that that they did not use accepted methodologies it could not fly. Wells apparently does not even to evaluate the evidence. He never said that know enough about the topic to point this out. scientists reject their methodology regardless Wells only singles out the two books that use of the evidence; he said that we cannot evalu- the word “link” in their descriptions, Mader ate their methodology because they do not pro- and Schraer and Stolze. The most accurate dis- vide one. Finally, Padian’s conclusion was not cussions can be found in Raven and Johnson, that there was no controversy, but that the con- Campbell et al., and Johnson. Archaeopteryx is troversy over bird origins was journalistic, not sometimes used as an example of how fossils scientific (Padian, pers. comm.). If Wells was can elucidate evolutionary relationships. Few taking notes at the conference, he didn’t do a books use Archaeopteryx as direct evidence very good job. for evolution; some books (e.g., Johnson) Although Wells smugly chides paleontolo- instead use the origin of whales as the princi- gists for their supposed views about bird evo- pal example of a transitional sequence. lution, he has not attended any meetings of the Society of Vertebrate Paleontology or the Ostrom Symposium on the origin of birds. He 48 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education
Figure 14. Textbooks’ treatment of and Wells’s grades for Archaeopteryx. WELLS’SEVALUATION ent scientifically incorrect data. What is most puzzling is that some books are given rather n grading textbooks on Archaeopteryx, the high grades compared to those given for other grading scheme, as usual, seems skewed to “icons.” Close examination of these books fail the books. Any book that does not I suggests that Wells misgraded them (Figure describe the transitional status of 14). For example, Wells gives Campbell, Archaeopteryx between reptiles and birds as Reese, and Mitchell a B, yet they clearly state “controversial” gets a D. As mentioned above, that Archaeopteryx is a transitional form there is no controversy about whether it is between dinosaurs and birds, for which a C or transitional, i.e, possesses structural features D would have been a more accurate grade both of its reptilian ancestors and of birds. To given Wells’s criteria. This negligent applica- get better than a D, a book would have to pres- tion of his own criteria calls into question the 49 Icons of Evolution? Why Much of What Jonathan Wells Writes about Evolution is Wrong Alan D. Gishlick, National Center for Science Education rigor of Wells’s evaluation and the value of his about Archaeopteryx are simply inaccurate. To grades whether or not one accepts his idiosyn- follow his lead would mislead students into cratic criteria. thinking that fossils tell us nothing about evo- lutionary relationships. Considering the fact WHY ARCHAEOPTERYX STILL FLIES that Wells doesn’t understand ancestry or phy- IN TEXTBOOKS logenetic reconstruction, and he isn’t even f anything, the value of Archaeopteryx as a aware of Archaeopteryx’s status in paleontol- pedagogical tool is increasing with all the ogy, should we really be inclined to trust any- Inew discoveries of feathered dinosaurs thing he says on these topics? from China. Literally every new fossil discov- ery has added to the utility of Archaeopteryx. Archaeopteryx is still one of our best examples References of a fossil that preserves ancestral features while showing descendant novelties. Britt, B. B., P. J. Makovickey, J. A. Gauthier, and N. Archaeopteryx is but one of many fossils Bonde. 1998. Postcranial pneumaticity in showing a clear genealogical connection Archaeopteryx. Nature 395:374–376. between dinosaurs and birds (Figure 12). Burnham D. A., K. L. Derstler, P. J. Currie, R. T. Bakker, Z. Zhou and J. H. Ostrom. 2000. Remarkable new bird- Much like Mark Twain’s, the reports of its like dinosaur (Theropoda: Maniraptora) from the Upper death are greatly exaggerated. Cretaceous of Montana. University of Kansas HOW TEXTBOOKS COULD IMPROVE Paleontological Contributions 13:1–14. THE USE OF ARCHAEOPTERYX Burgers, P., and L. M. Chiappe 1999. The wing of Archaeopteryx as a primary thrust generator. Nature AND TRANSITIONAL FORMS 399:60–62. extbooks could improve their explana- Chen, P.-J., Z.-M. Dong, and S.-M. Zhen. 1998. An tions of transitions in evolution by exceptionally preserved theropod dinosaur from the Tfocusing on transitional features (not Yixian formation of China. Nature 391:147–152. forms or individual animals) that are borne by Chiappe, L. M., S.-A. Ji, Q. Ji, and M. A. Norell. 1999. Anatomy and systematics of the Confuciusornithidae a series of closely related organisms. Further, (Theropoda: Aves) from the late Mesozoic of northeast- textbooks should be clear in presenting the ern China. Bulletin of the American Museum of Natural idea that in general fossils are not considered History. 242:1–86. to be direct ancestors, but as records of ances- Clark, J. M., M. A. Norell, and L. M. Chiappe. 1999. An tral features. Finally, in discussions of oviraptorid skeleton from the Late Cretaceous of Ukhaa Archaeopteryx, textbooks need to tighten up Tolgod, Mongolia, preserved in an avianlike brooding position over an oviraptorid nest. American Museum their descriptions and check their facts about Novitates 3265:1–36. the history of both Archaeopteryx and the Dingus, L. and T. Rowe. 1998. The mistaken extinction: dinosaur–bird relationship. Textbooks should dinosaur evolution and the origin of birds. W. H. be clear that birds are descendants of dinosaurs Freeman and Company, New York 332p. and that there are no other credible potential Forster, C. A., S. D. Sampson, L. M. Chiappe, and D. W. ancestral groups; they should also augment Krause. 1998. The theropod ancestry of birds: new evi- their rather short discussions of avian evolu- dence from the Late Cretaceous of Madagascar. Science 279:1915–1922. tion with some of the new fossil evidence from Garner, J. P., G. K. Taylor, A. L. R. Thomas. 1999. 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