FOSSIL-BASED DATING OF THE DIVERGENCE OF HOMINOIDEA AND CERCOPITHECOIDEA

Living Catarrhine primates comprise the sister groups Hominoidea (apes) and Cercopithecoidea (Old World monkeys). Here we use the fossil record to estimate the age of the hominoid-cercopithecoid divergence. The oldest known hominoid and cercopithecoid fossils date to 25.2 Ma, but this underestimates the true divergence date due to incomplete fossil preservation. We used the PBDB and primary literature to compile a database of hominoid and cercopithecoid fossils from the middle Miocene and earlier, comprising 63 fossil occurrences. We then used a new statistical method, the Adaptive Beta method, which is able to calculate confidence intervals on stratigraphic ranges without assuming uniform fossil recovery potential. We applied the Adaptive Beta method to our dataset to estimate the age of the earliest member of the combined group (Hominoidea + Cercopithecoidea), which is equivalent to estimating their date of divergence. We arrive at an early Oligocene divergence date of 30.8 Ma. This estimate is consistent with molecular estimates of the divergence date, as six recent studies found ages between 29.3 and 32.1 Ma with a mean of 30.8 Ma.