 Emile Zuckerkandl and Linus Pauling’s introduction and use of the hypothesis of a molecular clock provides a good example of the powerful utility of molecular data and was an important early episode in the history of molecular phylogenetics. The term “molecular clock” was coined in Zuckerkandl &amp; Pauling (1965), but they had already used it without naming it in earlier publications (Zuckerkandl &amp; Pauling 1962; Pauling &amp; Zuckerkandl 1963). The basic idea is fairly simple. Given some estimated rate of molecular evolution, the relative ages of branches and nodes may be estimated given some set of molecular data mapped onto a phylogenetic topology. Thus, molecular models of evolution were incorporated into phylogenetic methods  (§1.2.3).