It is generally true that evolving systems begin simply and become more complex in the evolutionary process. For those who try to understand the origin of a biochemical system, what is required is the development of an idea as to what simpler system preceeded the present one. Here we present an hypothesis that a universal tRNA molecule, capable of reading many codons may have preceeded the appearance of individual tRNAs. Evidence seems to suggest that this molecule may have been derived from a common ancestor of the contemporary 5S rRNAs and tRNAs.