The eocyte hypothesis and the origin of eukaryotic cells

Abstract

In the June 1984 issue of PNAS, James Lake and colleagues (1) published a provocative article in which they proposed that eukaryotes (animals, fungi, plants, and protists) evolved from a specific group of thermophilic prokaryotes, the “eocyte” archaebacteria (,1). Few questions capture the imagination of biologists like the origin of eukaryotic (nucleus-containing) cells such as our own, and as additional support accumulated (e.g., refs. ,2–,4) Lake's eocyte hypothesis garnered considerable attention. The idea that eukaryotes could have arisen from within an already diversified archaebacterial lineage was eventually overshadowed by Woese's (,5) “three-domains” view of life in which archaebacteria (including eocytes) represent a natural (i.e., monophyletic) group to the exclusion of eukaryotes and eubacteria (,5). In this issue of PNAS, Cox et al. (6) revisit the possibility of an archaebacterial origin for eukaryotes by using expanded molecular sequence datasets and ultra-modern phylogenetic approaches. Their analyses are a model of rigor and rekindle interesting and important ideas about the prokaryotic antecedents of eukaryotic cells.