Creationists have long insisted that the main evidence for evolution — the fossil record — involves a serious case of circular reasoning.That is, the fossil evidence that life has evolved from simple to complex forms over the geological ages depends on the geological ages of the specific rocks in which these fossils are found.
Ager, who is also Head of the Geology Department at Swansea University, notes the problem involved in trying to use minor differences in organisms (that is, what creationists would call horizontal changes, or variations) as time markers.
— If we read the record rather literally, it implies that organisms of new grades of complexity arose and radiated relatively rapidly."changes, however, are not really relevant to the measure of geologic time, since such changes occur too rapidly (e.g., the development of numerous varieties of dogs within human history) to be meaningful on the geologic time scale, and are reversible (e.g., the shift in the peppered-moth population of England from light-colored to dark-colored and back again).
Thus evolutionary changes in fossils are essential to real geologic dating, but they are impossible to prove. The dating of the rocks depends on the evolutionary sequence of the fossils, but the evolutionary interpretation of the fossils depends on the dating of the rocks.
Among these, in addition to those already cited, is Dr.
Derek Ager, current president of the British Geological Association.