On November 3rd 1977

The New York Times reported that a form of life that predates higher organisms had been discovered by scientists at the University of Illinois. The discoveries that formed the basis for this report were two papers in Proceedings of the National Academy of Sciences by a team led by Carl Woese, which included G. Fox, R. Wolfe, L. Magrum and W. Balch. These organisms came to be known, eventually, as Archaea. Remarkably, these organisms had been observed and in some cases cultured previously, but their phylogenetic significance never realized, because morphologically they resembled what we now call Bacteria; this had led to these two lineages being misclassified as Prokaryotes

This discovery was of fundamental importance for biology, and caused not only a sensation, but a revolution that continues to unfold. The reason for this is the manner in which the discovery was made, and the implications of the discovery for understanding the evolution of all life on Earth. The method of discovery was the creation of phylogenetic trees not based on superficial physiological characteristics, but on the similarity of molecular sequences of the 16S ribosomal RNA subunit. Being present in every cell, and highly conserved, this sequence provided a way to infer organismal lineages that has never been surpassed, despite numerous challenges over the years.

Thus, the Illinois work has formed the foundation for the field of molecular phylogeny, one of whose goals is the determination of the Tree of Life. The implication of the discovery of the Archaea is that there are three domains of life. Evolutionary studies have been completely transformed by this discovery. Moreover, related techniques have led to a explosive growth of the field of microbial ecology, where culture-free methods of identification are essential for exploring communities in the wild.