Speculations on the origin and evolution of metabolism.

An autotrophic origin of metabolism is described, which requires clays, transition state metals, disulfide and dithiols, U.V. and cyanide ion. A general scheme is proposed, involving the fixation of CO2 and N2, for the evolution of intermediary metabolism based on the evolution of a complex system from a simple one. The basic conclusion is that metabolism could have evolved from a simple environment rather than from a complex one.