Figure 5. Likelihood function for the time of origin of Archaeoceti, calculated as shown in Table 2 (but with a 0.0001 increment of origination volume). Note that maximum likelihood here (L = 1) corresponds to the time t = 49.5 Ma when the fossil record of Archaeoceti begins. L = 0.05 (the critical likelihood l employed here) when t is about 51.6 Ma. Given present evidence, there are about 2 chances in a thousand that archaeocetes existed and will be found as fossils at the Paleocene-Eocene boundary, and 6 chances in a billion that archaeocetes existed and will be found as fossils at the Cretaceous-Paleocene boundary.