ABSTRACT
Of all the clinically important emotions, anxiety may be the one with the closest parallels in other species and with the most ancient evolutionary heritage. Presumably this is because natural selection depends so closely on strategies for avoidance of danger that elements of what we call anxiety have been built into the response repertoire of organisms from the time when they first evolved a means of moving about in their world. If we could follow the steps by which anxiety evolved from its earliest precursors, it might give us some new insights into anxiety's component units and how they function together in such complex organisms as ourselves. To see for a moment how nature put such a state together may give us the perspective from which to find new ways to understand and treat its disorders.
