Sidney Altman, at Yale University, and Thomas Cech, at the University of Colorado Boulder, independently discover in the early 1980s that RNA can act as a biological catalyst — a function assumed to be exclusive to protein enzymes since the establishment of the classic biochemical dogma. Cech observes in 1982 that a certain RNA from the protozoan Tetrahymena cuts and splices itself autocatalytically, with no protein involved, removing an internal segment (intron) during its own processing. Altman demonstrates that an enzyme called ribonuclease P, responsible for processing transfer RNA, contains an RNA component that is the actual agent of catalytic activity, not the associated protein as had been assumed. The discovery of these RNA molecules with catalytic function — called "ribozymes" — requires revising the sharp distinction between nucleic acids as carriers of information and proteins as functional catalysts, and provides decisive experimental support for the "RNA world" hypothesis, according to which RNA, simultaneously capable of storing genetic information and catalyzing chemical reactions, may have preceded both DNA and proteins in the origin of life on Earth.