Frequency distribution of 1,000 estimates of the divergence time between lineages C and AB in Fig. 1, set to have occurred 3,000 Myr ago, obtained using a short (75 residues long), slow evolving (one replacement per site per 1010 years) protein, and using the split between A and B, set to 300 Myr ago, as the calibration point. T and M represent target (i.e., 3,000 Myr) and estimated mean (i.e., 4,084 Myr; see Table 1) times, respectively.