The discovery of DNA-binding motifs in ribosomal proteins has led to t
he conjecture that the transition of the ribosome from an RNA to an RN
P machine occurred by adding pre-existing proteins, Supportive, but ci
rcumstantial, evidence for the hypothesis is adduced from the finding
that many ribosomal proteins have a second function apart from the par
ticle. These extraribosomal functions are enumerated.