Carrillo: Using the number of existing primate species, along with measures of the genetic diversify among these primates and among the extinct primate species, our statistical model strongly supports the conclusion that the first primate developed around 81. 5 million years ago. Olson: Given that the oldest primate fossils discovered so far date back only 55 million years, your estimate of how long primate species' development has gone on is sheer speculation. The dialogue provides the most support for the claim that Carrillo and Olson disagree over whether ['primates have been around for more than 55 million years', 'fossils of the first primate species that developed have been discovered', "Carrillo's statistical model is a reliable way of dating the first appearance of primate species", 'the available sample of primate fossils is representative of the variety of primate species that have existed']