Saturday, November 28, 2009

The dinosaurs, and many other creatures such as the pterosaurs, mosasaurs, and ammonoids, went extinct at the end of the Cretaceous. There is considerable evidence that dinosaurs, after reaching a peak of diversity about seventy-four million years ago, began a gradual decline. Unquestionably, though, something delivered the coup de grĂ¢ce. In Chapter 8 I tell the story of the bitter, vicious controversy that raged over the reasons for the mass extinction that ended the Mesozoic. Many regard the dinosaurs’ demise with sadness. Many a kid has fantasized that somehow, somewhere, there is a lost forest where T. rex continues to prowl. But if the dinosaurs had not gone extinct, it would be most unlikely that we would be here. During the Mesozoic, our mammalian ancestors were small, nondescript, probably nocturnal creatures. While dinosaurs were dominant, there simply was no free ecological space for large mammals to occupy. Only after the extinction of the dinosaurs did the remarkable evolutionary radiation of mammals occur.

The dinosaurs were the lords of the Mesozoic. Their demise offers a deep lesson to us: The earth does not grant tenure. On the contrary, 99 percent of all species that have ever lived are now extinct. Even more sobering is the realization that several different hominid species have lived on Earth. Only one survives—Homo sapiens. We tend to think that the “sapiens” part of that name, our intelligence, gives us an edge that will allow us to escape the fate of other species. Well, we certainly have been successful in the short term—there are six billion of us on the planet, making us by far the most numerous species of large animal. By contrast, only about two thousand tigers survive in the wild. But the deepest lesson of the dinosaurs is the awful, incomprehensible depth of time. Sixty-five million years from now, will any of our descendants be alive? If so, will they be in any sense human? Will they remember any of our literature, our art, our science, our religions? After all, geological time shows that the only thing permanent is the fact of change. Evolution on Earth began with the first self-replicating molecules four billion years ago, and it will continue until the sun dies.

Dinosaurs - Recommended Reading

These include the anthology The Complete Dinosaur, edited by J. O. Farlow and M. K. Brett- Surman; David Norman’s Illustrated Dinosaur Encyclopedia; John Noble Wilford’s The Riddle of the Dinosaur; and Don Lessem’s Dinosaurs Rediscovered (originally titled The Kings of Creation). Almost as valuable as the Farlow and Brett-Surman anthology is the Encyclopedia of Dinosaurs (San Diego: Academic Press, 1997), edited by P. J. Currie and K. Padian. Good books on particular types of dinosaurs include John Horner and Don Lessem’s The Complete T. rex (New York: Simon and Schuster, 1993) and Peter Dodson’s The Horned Dinosaurs (Princeton, NJ: Princeton University Press, 1996). Gregory S. Paul’s Predatory Dinosaurs of the World (New York: Simon and Schuster, 1988) is interesting and contains the author’s own excellent illustrations but makes many very controversial claims about how fast these creatures ran and how they lived.

Some of the most interesting recent books on dinosaurs attempt to reconstruct their lives and habits. John Horner’s books can be particularly recommended as works that try to tell us about dinosaur behavior and lifestyles. His book Digging Dinosaurs: The Search That Unraveled the Mystery of Baby Dinosaurs (New York: Workman, 1988), cowritten with J. Gorman, tells about his discovery of dinosaur eggs and nests. These discoveries prompted Horner to name one dinosaur Maiasaura, which means “good mother lizard,” because of evidence that it kept nests and nurtured its young. A more recent book coauthored with E. Dobb, Dinosaur Lives: Unearthing an Evolutionary Saga (San Diego: Harcourt Brace, 1997), gives evidence for other aspects of dinosaur behavior.

There are two college-level textbooks on dinosaurs, Dinosaurs: The Textbook by Spencer G. Lucas (Dubuque, IA: William C. Brown Publishers, 1994) and The Evolution and Extinction of the Dinosaurs by David E. Fastovsky and David B. Weishampel (Cambridge: Cambridge University Press, 1996). Both are very good, well illustrated, and considerably livelier than the usual cut-and-dried textbooks.

A word of caution: There are many good books on dinosaurs. I have been able to list only a few of them here. However, there are also many very bad books on dinosaurs, especially books for children. These books are often written by people who do not know much about dinosaurs and who don’t mind making a few bucks by passing on their ignorance to others. Some years ago Don Lessem and other paleontologists formed the Dinosaur Society to safeguard against misinformation. If a book bears the seal of the Dinosaur Society, it will contain accurate information—otherwise, caveat emptor.