ABSTRACT
All organisms, including people, are products of the historical process of differential survival and reproduction that Charles Darwin called natural selection. This selective process is creative, producing attri butes that appear to have been designed to achieve adaptive functions: digestion, clear vision, circulation of the blood, escape from predators, and so forth. But attributes are naturally selected only if they eventually contribute to reproduction, or more precisely to genetic replication, hereafter called “fitness.” In evolutionary theoretical perspective, then, species-characteristic attributes must be explained in terms of their contributions to fitness. This is the “adaptationist program” that has guided most advances in biological understanding (Mayr, 1983).
