FIGURE 2.4 Comparison between Archaeopteryx, a Late Jurassic bird, and Compsognathus, a Late Jurassic theropod, as an approximate example of a transition between fossil forms as predicted by Darwin's hypothesis of natural selection. Reprinted by permission. From Paul (1988), The Predatory Dinosaurs of the World, Simon & Schuster, NY, p. 115.

composed of rocks pasted together that contained two different animals, a fossil non-avian theropod and a fossil bird. Ironically, both of the fossils were new to science at the time too, which initially gave it added credibility! Unfortunately, such mistakes can damage the credibility of a genuine find. Because of this potential pitfall, scientists are often quite reticent about reporting their preliminary findings when interviewed by mainstream journalists. Also, some journals will reject a paper if the results were previously published in a mainstream source, especially if the authors of the paper actively sought the publicity before they submitted it to the journal.

The ability to predict future observations on the basis of a hypothesis is one of the most effective and powerful ways to test its relative strength, and is central to scientific methods. An example of this predictability in paleontology was Charles Darwin's book On the Origin of Species, published in 1859, in which he predicted that transitional forms between major groups of organisms would be found in the fossil record. This prediction was followed two years later by the discovery of Archaeopteryx, a Late Jurassic fossil that shows numerous shared characteristics of dinosaurs and modern birds (Fig. 2.4). Hypotheses that do not predict observations in such a manner are incomplete (although not necessarily wrong), and consequently may not be built on a firm scientific foundation.

Two sequential steps can summarize the essence of hypothesis building: description and interpretation. The description phase involves the gathering of data (observations), which should be as meticulous and detailed as is humanly practical. For example, an analysis of hundreds of dinosaur bones might involve measuring and describing every feature of each individual bone, then performing statistical analyses of the quantitative data and verbal summaries of the qualitative data. Another description might require measuring and describing a dinosaur trackway that extends for 50 meters. Yet another description might be preceded by crawling on hands and knees in the hot summer sun to count the number of dinosaur eggshell fragments in a meter square. Descriptions, however, should be done with some objective in mind, such as testing hypotheses. The descriptive step requires extraordinary patience and trust in a process that has no guarantee of success.

Nearly all researchers consider the interpretation phase to be the most exciting part of the scientific process. In this phase, imagination is encouraged but, of course, only within the confines of what is described by the data. This is when scientists say that the spike on an iguanodontian hand was used for defense against predators (Chapter 11). This is when they explain that the missing tracks in a dinosaur trackway represents the dinosaur hopping on one foot (Chapter 14). This is when they say that the eggshell fragments in a dinosaur nest were broken originally by an egg-stealing dinosaur (Chapter 9). But this is also the phase when they might endure the critical scorn and derision of the rest of the scientific community, especially if they made major mistakes during their first step, the description. Good interpretations are nearly always preceded by good descriptions, although good descriptions are not guarantees of good interpretations.

If the first step is done well, then the second step may eventually result in an explanation that will satisfy most scientists. This is the case whether that explanation is based on original descriptions or a reinterpretation of the descriptions of others, maybe long after those original researchers have died. A hypothesis should not be made with the expectation that it will please all scientists. Although the complete dismissal of egos is unrealistic, scientists should also expect to develop a skin as thick as an ankylosaur (Chapter 12) and separate themselves personally from their work. As a scientist or thinking human being, getting used to constructive criticism and learning from it each time should result in improvement with each new attempt to answer the questions: "What is this?" or "How did this happen?"

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