We usually think of Charles Darwin as having made his most important contributions to the field of biology. But while his pioneering work in natural selection certainly changed the theory and practice of biology fundamentally and forever, the effect of his work and his ideas was also substantial in the field of psychology. This might seem to be a far reach from biology, but there are clear connections between the study of the evolution of a species or of all species and the study of the evolution of personality within the individual.
One of the most important things to remember when contemplating the contributions that Darwin made is his insistence on the constancy of change. He demonstrated beyond any possibility of a doubt that life is change, that living forms develop constantly from one form to another. He was, of course, in general referring to the change that occurs between generations as the result of natural selection acting on the variability that exists among individuals in a species (Gould, 2002, p. 27). However, psychologists were quick to understand that Darwin's insistence on the powerful force of change in all living creatures had implications for human development as well.
Canadian psychologist Irwin Silverman argues that there were a number of reasons why psychologists found the evolutionary principles outlined by Darwin so appealing. The first of these was that they helped to bring to psychology (one of the "soft" sciences) something of the rigor of the hard sciences, with the accompanying promise that psychology would thus be able to make the same kinds of substantial leaps forward in the understanding of human behavior that biologists were making in their own work (http://www.human-nature.com/ep/articles/ep0119.html).
There was also the belief among many psychologists that apart from scientific rigor there was also the fact that Darwinian theory offered a template for charting human behavior. One of the mos...