Abstract
The molecular evolutionary clock hypothesis may be defined as the thesis that changes in amino acid sequence of a specific protein proceed at a constant rate in regard to time. Since it was proposed thirty years ago, this concept has been the primary molecular basis for evaluating organismal relationships (phylogenetic trees) and for estimating times of divergence of the various branches of those trees. We will consider recent developments in molecular biology and their relationship to the molecular clock concept. We will also discuss the lack of any theoretical basis for the molecular evolutionary clock and evaluate experimental data to show that there has been very little experimental verification of a constant rate of change. Finally, we will examine the relationship of the molecular clock hypothesis to some theological and philosophical beliefs.