USING DINOSAURS TO DEMONSTRATE THE TESTABILITY OF EVOLUTIONARY HYPOTHESES

There is a common public perception, shared by many secondary and college students, that the historical sciences are inherently untestable. This applies in special measure to evolutionary theory. It is therefore important that students be presented with real examples of how hypotheses of evolutionary relationship can generate predictions that are subject to test. Because of the continued rapid pace of new fossil discovery, the fossil record can be used quite effectively to illustrate how particular evolutionary hypotheses have been supported by subsequent fossil discoveries. In particular, the fossil record of the most charismatic of all fossil vertebrates -- the dinosaurs -- provide many such teaching opportunities.

Hypothesized patterns of evolutionary relationship generated by cladistic analysis yield predictions of the relative order of appearance of different anatomical characters in the fossil record. Cladograms can also extend the known temporal ranges of fossil taxa, and identify “ghost ranges” where fossil representatives are currently unknown. Evolutionary hypotheses also result in expectations concerning the general character states of transitional forms between known sister taxa and their presumed common ancestors. The recent history of dinosaur discovery (particularly for coelurosaur theropds) provides an opportunity to illustrate how these various evolutionary predictions have been met by new dinosaur finds. Students can construct their own cladograms based on simple lists of characters for a select group of dinosaurs. They can also recognize the patterns of relative appearances and ranges implied by cladograms. By looking at the progressive growth in our knowledge of the dinosaur fossil record over the past 20 years, students can see how new discoveries can support or modify proposed evolutionary relationships.