Figure 1. Divergence of giraffe and okapi from a common ancestor.

Using the average pairwise synonymous substitution divergence (dS) estimates between giraffe, okapi and cattle as calibrated by the pecoran common ancestor (27.6 mya), the divergence of giraffe and okapi from a common ancestor is estimated to be 11.5 mya. Okapi image adapted from a photograph by Raul654.