Origins of life: The first two billion years Read full paper at: http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v387/n6634/full/387662a0_fs.html EÖRS SZATHMÁRY

Eörs Szathmáry is in the Department of Plant Taxonomy and Ecology, Eötvös University, Ludovika tér 2, H-1083 Budapest, and at the Collegium Budapest, Szentháromság u. 2, H-1014 Budapest, Hungary.

The problems associated with defining the origins of, and transitions between, different levels of biological organization receive increased attention these days, and rightly so. New discoveries and models help us to account for the processes that resulted in new ways of storing and retrieving hereditary information. These processes often relied on the formation of higher-level evolutionary units from previously unlinked replicators — small units that can replicate independently1. This was the subject of a recent meeting*, organized by the Swedish Natural Science Research Council, at which topics ranging from the origin of the first replicators to the emergence of multicellular eukaryotes were discussed. The origin of non-enzymatic replication is still an unsolved problem. Although artificial replicators can grow without a replication enzyme (replicase) in a test tube2, they are not a historically realistic recapitulation of what could have happened on the early Earth. But there are three promising lines of research: replication of nucleic acids on a surface; in vitro construction of a catalytic RNA (ribozyme), which could act as a generalized replicase; and formation of oligonucleotides by ligating together smaller nucleic-acid units.