Considering that birds are an intrinsic part of modern daily life and culture, it is not surprising that their evolutionary origin has been the topic of significant interest and controversy. A rapidly growing body of evidence supports the hypothesis that birds are evolutionarily nested within theropod dinosaurs—a group that includes the iconic Tyrannosaurus and Velociraptor (Chiappe 2009). These data derive from osteological studies, as well as from information about sensory capabilities (Witmer and Ridgely 2009), reproductive traits (Zelenitsky 2006), growth patterns (Erickson et al. 2009), integumentary features (Norell and Xu 2005), and genomic size (Organ et al. 2007). Such overwhelming evidence has led to a broad consensus among evolutionary biologists, who today consider birds to be the descendants of Mesozoic dinosaurs. Any well-substantiated new view that allows us to step back and revisit this established hypothesis should stimulate research and be embraced with enthusiasm, but Alan Feduccia's Riddle of the Feathered Dragons: Hidden Birds of China does nothing of the sort. Instead, the book misleads its readers into believing that the theropod hypothesis hinges on scant evidence and is the empirical equivalent to Feduccia's vaguely presented alternatives.
The author begins by building a conspiracy theory in which the main villains are the cladists, who, like computational shamans, reveal what they see in their character matrices. He disdainfully equates dinosaur paleontology—and paleontology in general—with a second-rate scientific discipline more worthy of tabloids than respected journals. Recognized periodicals such as Nature and Science, together with their editors, are the alleged accomplices of the indoctrinated cladists, and virtually anyone connected with the view that certain theropods are the most immediate predecessors of birds is painted negatively.
Early in the book, Feduccia tells us that the most important issues are “whether birds are living theropods and whether flight evolved from the ground up rather than from trees down” (p. 23). However, for most researchers, and presumably for this audience, the more important questions are Who are the closest relatives of birds? and How did these animals evolve flight? This difference in scope sets the book's entire tone, because Feduccia is clearly more interested in disproving the theropod hypothesis than in providing support for an alternative.
We learn soon enough about the author's methodological strategy: “The possibility that one key synapomorphy, if falsified, would reduce all the other synapomorphies to the status of parallelism and hence irrelevant to the debate, should be a lesson to the more dogmatic cladists” (p. 21). This and other statements reveal Feduccia's precarious understanding of the methodology he so despises. Astonishingly, he argues that “cladistic approaches tend to group animals as ecological equivalents (ecomorphs) without any necessary regard to actual relatedness” and emphasizes that the “overarching problem in cladistic approaches has been practitioners' tendency to ignore or dismiss contradictory evidence” (pp. 2–3). Since when has cladistics been a methodology that disregards either relatedness or controversy? Indeed, a fundamental approach of cladistics is the optimization of characters against each other—characters that by nature may provide a contradictory phylogenetic signal!
Throughout Riddle of the Feathered Dragons, Feduccia mistakenly equates the origin of birds with the origin of flight and associates the theropod hypothesis with the ground-up view of flight origins. He leads his charge by arguing that a corollary of the current consensus is that “all avian flight adaptations and sophisticated anatomical aerodynamic architecture evolved in a context other than flight” (p. 1). Such a claim, however, ignores abundant arguments that view the evolution of flight-correlated structures as a series of transformations that unfolded over millions of years and spanned the evolutionary transition from nonavian theropods to modern birds (Gatesy 2002). Furthermore, by arguing that the theropod hypothesis presumes that flight originated from the ground up, Feduccia ignores the research that endorses a trees-down interpretation within the phylogenetic context of the theropod hypothesis (Zhang et al. 2002, Xu et al. 2003).
What is basic to the author's argument—and what inspires the book's subtitle—is the claim that certain nonavian theropod lineages (dromaeosaurids, troodontids, oviraptorosaurs, and therizinosaurs) should be reclassified as birds. In this context, regardless of whether these “hidden birds” were flighted like the “four-winged” Microraptor or secondarily flightless, Feduccia interprets them as evolutionary divergences between Archaeopteryx and living birds. In doing so, he brushes off three decades of phylogenetic analyses (naturally, conducted by cladists!) indicating that these dinosaurs lie outside the clade that includes Archaeopteryx and all other birds. The author also dismisses studies indicating that the external integumentary filaments of a number of Chinese nonavian theropods should be most parsimoniously interpreted as homologous to feathers (Norell and Xu 2005, Zhang et al. 2010).
In addition, resting on Dollo's law of irreversibility, Feduccia questions whether it is “biologically possible to reevolve the already greatly foreshortened forelimbs” of a number of nonavian theropods into the elongate wings of birds. He details well-known exceptions to Dollo's law, but ends by proclaiming, “Certainly ‘compsognathid’ arms could not reelongate into Archaeopteryx wings” (p. 224). No modern study has hypothesized a direct ancestor— descendant relationship between compsognathid theropods and Archaeopteryx, but the book is filled with equally unreasonable statements about the limits of evolutionary change.
Riddle of the Feathered Dragons is also strangely infused with lectures on the morality of science. Feduccia scolds editors about how “scandals are sensational, but uncritical editing that permits careless and flawed articles to appear in esteemed journals is more troubling” (p. 10). He warns paleontologists that “if the science of dinosaur paleontology does not embrace a more self-critical ethos, it will degenerate into endless speculations and tabloid sensationalism" (p. 19). Reacting to what he considers to be ideological and unsubstantiated claims that the integumentary coverings of many nonavian theropods are feather homologues, Feduccia quotes Carl Sagan: “Extraordinary claims require extraordinary evidence.” But given the number of publications supporting the theropod origin of birds, a claim to the contrary is what is extraordinary; however, Riddle of the Feathered Dragons provides nothing remotely close to the required extraordinary evidence. Ultimately, Feduccia's entire oration about the ethics of science feels empty, in light of how poorly the book applies these moral teachings to its own agenda.
When the book comes to the discussion about the closest relatives of birds (for most of us, the core question), Feduccia presents a vague alternative: Their ancestry can be traced back to either a basal archosaur or a dinosauromorph. Such a hypothesis is so wide ranging that it tells us nothing. Does he think the closest relative is an animal like Longisquama?. (He remarks on the “birdlike” appearance of this poorly known diapsid reptile, which he considers to be an archosaur.) Or does he think one of the disparate lineages of basal archosaurs (aetosaurs, phytosaurs, and rauisuchians, to mention a few) is actually more closely related to birds? Or are the small bipedal dinosauromorphs, such as Marasuchus, those that he concludes to be the bird's next of kin? All of these very different organisms fall within the basal archosaur—dinosauromorph hypothesis that the author so cursorily endorses.
After 358 pages, Riddle of the Feathered Dragons fails to support a clear alternative hypothesis of bird origins that counters the consensus of their being the living descendants of theropod dinosaurs. Amid a profusion of unfounded and rhetorical statements that, at times, sound more like divine revelations, Feduccia quotes T. H. Huxley—Darwin's famous “bulldog” and staunch defender of the theropod hypothesis—saying, “a good book is comparable to a piece of meat.” If Huxley were alive, I think he would agree that Riddle of the Feathered Dragons tastes more like cabbage.
