Figure 10
Histogram showing the orthologs of mouse:rat intertaxon pairs using f4 metric, the fraction identical for four fold redundant codon systems (n > 100). While the separation of orthologs from paralogs is larger, the distribution is wider. We do not reject f4 as a dating tool, but only that its use recognizes its particular advantages (broader sample size) and limitations (greater heterogeneity in microscopic rate constants).