Carl Woese, Discoverer of the Archaea, RIP

One of the first things that students learn today about the diversity of life is the concept of the Three Domains of Bacteria, Archaea, and Eukarya. In the past, they would have learned about the Five Kingdoms — Prokaryotes, Animals, Plants, Fungi, and Protists —a concept popularized by the late Lynn Margulis, but we now know that the animals, plants, and fungi are relative newcomers on the evolutionary scene, and that the "prokaryotes" actually contain two ancient lineages, the Bacteria and Archaea, which split long before the eukaryotic kingdoms.

Carl Woese in 2006, via U Illinois

For this insight, we can thank Carl Woese, who passed away just before the New Year at the age of 84 (U Illinois press release, NY Times obituary). Woese made his discovery in the 1970s, when sequencing DNA and RNA was anything but routine. At that time, the prokaryotes were classified primarily by physiological characteristics and morphological appearance. There was little attention paid to microbial evolution, except in a speculative way, simply because there was no easy way to go about studying it.