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Carl Woese
1928–2012; identified archaea 1977· Scientist· Microbes & cells
Well establishedStrong fossil, genetic or geological evidence.
American microbiologist who used genetic sequences to discover archaea, a separate major branch of life.
See it on the Life map →What happened
Woese (1928–2012), at the University of Illinois, compared ribosomal RNA, a molecule every cell uses to build proteins, across many microbes. In 1977 he and George Fox found that methane-making microbes differed from ordinary bacteria as much as from humans. He called them archaebacteria, now archaea, and in 1990 proposed three domains of life: Bacteria, Archaea and Eukarya (plants, animals, fungi and other cells with a nucleus). Many senior biologists, including Ernst Mayr, resisted at first.
Why it matters
He made gene sequences the main tool for mapping life's family tree, revealing that most of life's diversity is microbial.
Discoveries and legacy
His 1977 and 1990 papers in the Proceedings of the National Academy of Sciences; the 1996 genome of a methane-making archaeon confirmed its distinctness. He won the Crafoord Prize in 2003.
Still debated
Newer data suggest complex cells arose from within archaea, which would mean two primary domains rather than three; the debate continues.
Connections (2)
▸Carl Woese showed the deep split within Bacteria & archaea: the microbial worldWell established
The connection
Before Woese, all microbes without a nucleus were lumped together as bacteria. Comparing ribosomal RNA sequences, he showed that methane-producing microbes, and later many salt- and heat-loving ones, formed a separate group as distant from bacteria as from humans. The single microbial world became two deep lineages: bacteria and archaea.
When and how
University of Illinois at Urbana-Champaign, 1977, by Carl Woese and George Fox; published in the Proceedings of the National Academy of Sciences.
The evidence
Archaea have chemically different cell membranes and gene-reading machinery closer to ours; whole-genome sequencing from 1996 onward confirmed the split.
Debates and open questions
What the last common ancestor of bacteria and archaea was like, and where exactly the root of the tree of life lies.
▸Carl Woese redrew the roots of Common descent & the tree of lifeWell established
The connection
Earlier trees of life were drawn mainly from anatomy and had little room for microbes. Woese built the first universal tree from ribosomal RNA, which all cells share. It showed three great branches, Bacteria, Archaea and Eukarya, with plants and animals as small twigs. Gene sequencing became the standard way to draw the tree.
When and how
University of Illinois: archaea discovered in 1977; the three-domain proposal, with Otto Kandler and Mark Wheelis, in 1990.
The evidence
Thousands of genomes, including microbes known only from environmental DNA, fill out the tree he outlined; the deep split between bacteria and archaea holds.
Debates and open questions
Whether complex cells form a third domain or branch from within archaea, as Asgard archaea found since 2015 suggest; gene swapping also blurs the roots.