University of Southern California - Center for Computational and Experimental Genomics
Molecular-based times of divergence often considerably pre-date the earliest known fossil representatives of the groups studied. For the order Primates, molecular data uniformly suggest a mid-Cretaceous origin, some 90 million years ago, whereas the oldest fossils are known from basal Eocene rocks only 54-55 million years old. The incompleteness of the fossil record suggests that times of divergence estimated from molecular data should be older than the oldest known fossils, but an adequate quantification of that incompleteness is needed to evaluate the significance of discrepancies between molecular and fossil-based estimates. I will present a new statistical method, based on an estimate of species preservation derived from a model of the pattern of diversification of the group, that suggests a Cretaceous divergence of Primates, providing paleontological corroboration for the time of origin predicted by molecular data. The method also suggests that no more than 7% of all primate species that have ever existed are known from the fossil record. The new approach includes all aspects available to the timing of evolutionary events: The fossil record, molecular evidence, extant species, and diversification models for the investigated clade.