Structural Reduction in Evolution

Abstract

1. While there is no doubt that currently accepted factors (mutation, selection, genetic drift, and migration) (Neel and Schull, 1954; Dobzhansky, 1955a) play a major role in determining the direction of evolution, it is suggested that a process of considerable importance has been overlooked. The probable effect of mutations will be towards structural reduction. If the structure controlled by the locus in question has no adaptive significance, then it will be reduced in the course of time. 2. It is suggested that some of the major and formerly unexplained changes which have occurred in human evolution are the results of probable mutation effect. Reduction in the size of the teeth and face and of the skeletal and muscular systems may have been brought about by such a mechanism, as a result of changes in the principal human adaptive mechanism, culture. The rise and distribution of depigmentation is treated in like manner. 3. Finally it is urged that changes in all outstanding morphological characteristics b...