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Introduction: Dinosaurs and Birds
By Brad
One issue in palaeontology surpassed the K-T extinction in both scientific and popular attention in the final years of the twentieth century: the origin of birds. The highly modified skeleton of a bird has always made it difficult for evolutionists to recognize their exact ancestors among the reptiles. Numerous possibilities have been proposed over the years, but the most famous of all is the theory that birds evolved from carnivorous dinosaurs. If birds are indeed descended from dinosaurs, then the terrible lizards are not truly extinct, but are still with us in winged and feathered form.
The brilliant evolutionist Thomas Huxley was the first to suggest that birds had dinosaur ancestors. He introduced his theory in 1868, just seven years after the discovery of Archaeopteryx, an animal still generally regarded as the oldest known bird. Huxley’s ideas gained support and persisted well into the twentieth century. The first apparent flaw was not pointed out until 1926, when Gerhard Heilmann claimed that dinosaurs lacked the collarbones necessary for a wishbone to evolve. Heilmann’s book pushed the origin of birds back to the early archosaurs, the common ancestors of dinosaurs and crocodiles. Subsequent theories placed the origin of birds with Triassic crocodiles, or various kinds of arboreal reptiles. With the dinosaur hypothesis discredited, the ancestry of birds returned to being a very uncertain topic.
John Ostrom revived the old dinosaur theory in the 1973. His careful comparisons of Archaeopteryx and Deinonychus, a recently discovered dromaeosaurid theropod, showed startling similarities in the details of the skeleton. Heilmann’s observation that theropods lacked collarbones was shown to be untrue. Alan Grant’s raptor site in Montana provided additional skeletal evidence linking theropods and birds. His studies of the velociraptor braincase showed that it was especially advanced and birdlike. Of course, there were always critics who claimed that this evidence was an example of convergent evolution, or was present in a broader group of archosaurs. But as the evidence linking dinosaurs to birds increased, it became more difficult to object. A spectacular skeleton of a small carnivorous dinosaur found in China in 1996 even appeared to show a feathery body covering. It appeared as if the case would soon be closed, and dinosaurs would be recognized as the true ancestors of modern birds.
The feathered dinosaur was a short-lived idea. InGen’s “lost world” of cloned dinosaurs became public knowledge in late 1997, and their velociraptors, recreated as flawlessly as the technology allowed, were clearly scaly animals. A Chinese fossil previously seen as a feathered dinosaur was reinterpreted as the remains of muscle fibres, a misidentified Cretaceous bird, or an intentional hoax. As a result of the feather controversy, the entire theory that birds are dinosaur descendants was soon under attack. Alan Grant, refusing to abandon his theory, began to deny that InGen’s animals were dinosaurs. But to his opponents, he was just trying to avoid the issue. The velociraptors on Isla Sorna were certainly real, and the feathered dinosaurs were not.
The problem now rested in studying these velociraptors to test the theories. There had still not yet been a scientific expedition to Isla Sorna. There was no official decision from Costa Rica or the United Nations regarding the fate of the island. Many palaeontolgists worried that the dinosaurs would be destroyed, and the debate would never be fully resolved. This novel documents the expedition of three scientists, determined to destroy the dinosaur bird link, on Isla Sorna in late 2001.
4/12/2002 9:53:00 PM
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