What is the basis of the three domain system?

The basis of the three-domain system lies in molecular phylogenetics, particularly the analysis of ribosomal RNA (rRNA) sequences. Carl Woese’s research in the 1970s and 1980s demonstrated that rRNA sequences could reveal deep evolutionary relationships among organisms. His work showed that the rRNA sequences of Archaea, Bacteria, and Eukarya were sufficiently distinct to warrant their classification into separate domains, leading to the adoption of the three-domain system in 1990.