title: Molecular clocks.
abstract: In the 1960s, several groups of scientists, including Emile Zuckerkandl and Linus Pauling, had noted that proteins experience amino acid replacements at a surprisingly consistent rate across very different species. This presumed single, uniform rate of genetic evolution was subsequently described using the term 'molecular clock'. Biologists quickly realised that such a universal pacemaker could be used as a yardstick for measuring the timescale of evolutionary divergences: estimating the rate of amino acid exchanges per unit of time and applying it to protein differences across a range of organisms would allow deduction of the divergence times of their respective lineages (Figure 1).
authors.affiliation: School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia; and Earth Sciences Section, South Australian Museum, North Terrace, Adelaide SA 5000, Australia. Electronic address: mike.lee@samuseum.sa.gov.au.
authors.forename: Michael S Y
authors.initials: MS
authors.lastname: Lee
authors.affiliation: School of Life and Environmental Sciences, University of Sydney, Sydney NSW 2006, Australia. Electronic address: simon.ho@sydney.edu.au.
authors.forename: Simon Y W
authors.initials: SY
authors.lastname: Ho
mesh_terms: D019943:Amino Acid Substitution; D005075:Biological Evolution; D019143:Evolution, Molecular; D010802:Phylogeny