Origin of Life

Abstract

Establishing the nature of the processes by which life originated is one of the most fundamental unsolved scientific problems. Fifty years of study have enabled us to assemble many pieces of the puzzle but have also left a number of critical gaps in our understanding. Even the issues of when and where life originated are still poorly constrained, but life probably appeared on Earth between about 4.2 Ga and 3.5 Ga ago. There is good evidence that the current DNA–RNA–protein basis for life developed from a stage known as the ‘RNA world’ in which RNA performed the information-storage and catalytic roles currently performed by DNA and proteins. Direct formation of the RNA world from prebiotic chemistry seems unlikely, so much current research focuses on possible precursors to the RNA world. Various suggestions for pre-RNA worlds have been made, but none has yet proved entirely satisfactory. A number of terrestrial and extraterrestrial processes can produce prebiotic organic molecules, but there are still problems in obtaining the right molecules in sufficient quantities.