In 1978, Carl Woese, an American microbiologist defined Archaea as a new domain based upon genetic relationships that divided life into 23 main divisions and three domains: Bacteria, Archaea, and Eucarya.

Carl Woese was an American biophysicist and microbiologist who revolutionised evolutionary biology. In 1977, he uncovered the ‘third domain of life’. He achieved this by defining Archaea (a group of single-cell prokaryotic organisms) – by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by him. Prior to publication of Woese’s paper, scientists believed that all life on Earth belonged to two lineages – eukaryotes and prokaryotes.

Woese and his colleagues determined that prokaryotes were actually made up of two different groups of organisms – true bacteria and Archaea, with Archaea more closely related to eukaryotes than bacteria. Carl Woese received many honours and awards for his work and passed away in 2012, aged 84.