Promethean evolution: A comparison of the immune and neural systems

In contrast to normal Darwinian evolution involving adaptation to past challenges, it has been suggested that evolution has devised two unique biological mechanisms to permit the host to anticipate future challenges: the adaptive immune response and neural memory functions. Certain phenomenological similarities, some sharing of names, and the participation in both systems of a group of physiologically active molecules suggested to many that the two might be intimately related. This article compares the two systems in terms of the familiar parlance of immunology-specificity, repertoire, degeneracy, memory, mediators, pathways, and genetics-to show that they differ in most respects, except insofar as they may utilize some of the same agents, many of which participate in the normal functions of other tissues and systems of the body. Indeed, this very difference provides a further demonstration of the wonders of the evolutionary process.