Phylogeny and beyond: Scientific, historical, and conceptual significance of the first tree of life

Abstract

In 1977, Carl Woese and George Fox published a brief paper in PNAS that established, for the first time, that the overall phylogenetic structure of the living world is tripartite. We describe the way in which this monumental discovery was made, its context within the historical development of evolutionary thought, and how it has impacted our understanding of the emergence of life and the characterization of the evolutionary process in its most general form.

Fig. 1.

Ribonuclease T1 oligonucleotide fingerprint. As outlined in the text, data reported in the paper by Woese and Fox (1) in 1977 consisted of catalogs of oligonucleotide sequences derived from RNase T1 digestion of small subunit (SSU) rRNAs. The first step of the analysis involved resolution of RNase T1 digests of 32P-labeled rRNA by 2D electrophoresis and locating labeled oligonucleotides on the 80 × 100-cm sheet of electrophoresis paper by autoradiography. The result, an RNase T1 fingerprint of the specific RNA, is shown; notations were made by Woese during the analysis of archaeal rRNAs. Larger phylogenetically informative oligonucleotides are in the upper one-half of the pattern.

Fig. 2.

Diagrammatic phylogenetic tree used to illustrate the proposal of three phylogenetic domains in 1990. Modified from Woese et al. (23).