any theory to account for the evolution of organisms over successive generations. One early and influential example was the theory of evolution by use or disuse (see Lamarckism). Nowadays, the most widely accepted is an updated version of Charles Darwin’s theory of evolution through natural selection, called neo-Darwinism (see Darwinism). Theories concerning specific aspects of evolution include coevolution, exaptation, neoteny, punctuated equilibrium, and recapitulation theory. Opposed to all theories of evolution is the doctrine of creationism. The application of evolutionary principles permeates different subdisciplines within psychology, including clinical science, cognitive psychology, and neuroscience. For example, the influence of evolutionary theories can be seen in studies conducted to determine whether particular clinical disorders (e.g., depression,
anxiety) are in fact psychological adaptations or in assertions that emotions evolved to serve primary functions (particularly to motivate and communicate) that would enhance survival.