Evolution at All Scales in the Vertebrate Fossil Record

Abstract

The fossil record of vertebrates provides abundant evidence for both the fact and the theory of evolution (Carroll, 1997; Prothero and Schoch, 1994). In support of the fact that evolution has indeed occurred, the vertebrate fossil record clearly documents evolutionary change alonglineages, that is, along direct lines of ancestors and descendents. The fossil record also shows step-wise evolutionary changes resulting in the emergence of new kinds of vertebrates from pre-existing kinds—for example, the origin of mammals from the “mammal-like” reptiles. In support of the theory that natural selection, in particular, has been largely responsible for evolutionary change, the fossil record shows that the numerous “transitional” forms that lived in the past—far from being nonviable “monsters”—were functionally integrated organisms that were well adapted to their ecological roles. Finally, the vertebrate fossil record preserves certain large-scale phenomena, such as radiations and trends, which show that evolutionary forces can act over very large time scales.