The evolutionary history of ribosome was traced onto the three-dimensional structure of its rRNA and r-protein components. Ages of components were colored with hues from red (ancient) to blue (recent). Phylogenomic history shows that primordial metabolic enzymes preceded RNA-protein interactions and the ribosome. The timeline of life derived from a universal phylogenetic tree of protein domain structure at fold superfamily level of complexity is shown with time flowing from left to right and expressed in billions of years according to a molecular clock of fold structures. The ribosomal timeline highlights major historical events of the molecular ensemble. History of the conserved ribosomal core [29] overlaps with that of diversified life [48], suggesting that episodes of cooption and lateral transfer have pervaded early ribosomal evolution.
