"Teaching the controversy" is controversial. Sides have been drawn.
On one side, most intelligent design (ID) proponents want students to become familiar with the evidence cited in support of evolution and with evidence against it. In short, they recommend that educators "teach the controversy" about evolution1
On the other side, most evolutionary biologists reject this proposal. They insist that there is no controversy about evolution. According to Eugenie Scott and Glenn Branch of the National Center for Science Education, while debate takes place about "the patterns and processes of evolution…it is scientifically inappropriate and pedagogically irresponsible to teach that scientists seriously debate the validity of evolution."2
Is there no controversy among scientists? Are the debates merely about the patterns and processes of evolution, or does the scientific evidence raise sufficient doubts about the validity of biological evolution? Recent work on bird origins helps address these questions.
Evolution's critics often cite the virtual absence of transitional intermediates in the fossil record as a significant problem for the theory. If evolutionary processes explain life's history, then it's reasonable to expect an abundance of fossil intermediates documenting the emergence of new life-forms.
Evolutionary biologists respond to this challenge by claiming that there are transitional forms in the fossil record. To buttress this assertion they frequently point to the "feathered" dinosaur fossils, interpreted as transitional intermediates between birds and theropod dinosaurs (like the raptors in the movie Jurassic Park).3
The bird-dinosaur theory for the origin of birds has become "orthodoxy" among evolutionary biologists. Based on morphological (anatomical, physical) similarities between birds and theropods, a majority of evolutionary biologists conclude that birds evolved from these bipedal dinosaurs. In this scenario transitional forms between theropods and birds should be uncovered in the fossil record. A few years ago, the discovery of certain theropods (dated at about 125 million years in age) in the Yixian Formation of China's Liaoning province seemed to satisfy this key prediction. These fossils possess structures that have been interpreted as feathers by some paleontologists, making them candidates for transitional intermediates between dinosaurs and birds.
However, new work by an international team of paleontologists challenges this standard evolutionary assertion.4 Detailed analysis of a new fossil specimen of Psittacosaurus, a dinosaur thought to have no place in bird ancestry, indicates that the features interpreted as theropod feathers are actually frayed integument (skin). Researchers also amassed additional evidence that severs the evolutionary link between birds and dinosaurs. For example, they demonstrated that the foot-and-toe structures of birds and theropods are fundamentally different even though superficially they appear to be similar. The team also showed that all the "feathered" dinosaur transitional forms occur in the fossil record 30 million years after the appearance of the first true birds. Plus, some of the "feathered" dinosaurs, such as Caudipteryx, are not dinosaurs at all-rather, they're flightless birds.
According to Alan Feduccia, the paleontologist who led the research team that investigated Psittacosaurus, constant promotion of the bird-dinosaur theory in National Geographic, Nature, and Science creates a false sense of confidence about how birds originated.5 In the midst of this publicity, the study conducted by Feduccia's team raises serious questions about the validity of the most widely held evolutionary explanation for bird origins. Feduccia says that "[t]he theory that birds are the equivalent of living dinosaurs and that dinosaurs were feathered is so full of holes that creationists have jumped all over it, using the evolutionary nonsense of 'dinosaurian science' as evidence against the theory of evolution."6
Feduccia's assessment, and the work of his team, are meaningful in light of the "teach the controversy" hullabaloo. Could it be that there are mainstream ideas in evolutionary thought-like the bird-dinosaur theory-that are considered absurd, even by evolutionary biologists? If so, then aren't evolution's critics justified in identifying significant problems that confront evolution?
Apart from the bird-dinosaur theory, evolutionary biologists offer no real explanation for bird origins. Consequently one of the best examples for evolutionary transitional intermediates disappears from the fossil record. Shouldn't students be taught about such controversies? It seems pedagogically responsible to do so. Students can decide whether or not biological evolution is valid based on an objective presentation of the evidence. "Teaching the controversy" shouldn't be controversial at all.