Early evolution and the origin of eukaryotes.

Our understanding of evolutionary relationships in the eukaryotic world has been revolutionized by molecular systematics. Phylogenies based upon comparisons of rRNAs define five major eukaryotic assemblages plus a series of paraphyletic protist lineages. Comparison of conserved genes that were duplicated prior to the divergence of eubacteria, archaebacteria, and eukaryotes, positions the root of the universal tree within the eubacterial line of descent. In this review a novel model is presented which uses the rRNA and protein based phylogenies to describe the evolutionary origins of eukaryotes.