Finally, based on phylogenetic analyses of mtDNA sequence data, Collins and Dubach (2000a) proposed that Ateles paniscus is the most basal taxon within the spider monkeys and the sister
group to all other modern forms. They also proposed that this taxon was the first one to be isolated, by the separation of the Guianan region from the Amazon around 3.3–3.6 Ma. Then, A. belzebuth,A. chamek, and A. marginatus probably shared a common ancestor in the southern and northwestern Amazon basin around 2.4 Ma. According to this hypothesis, Ateles geoffroyi and A. hybridus would probably have diverged between 3.1 and 2.0 Ma and likely originated from a population of spider monkeys located in northern Colombia, within the current geographic range of A.hybridus. Some of these primates would first have dispersed into Central America and secondarily dispersed back into South America along the Pacific coast of Colombia and Ecuador, giving rise to A. fusciceps. It is noteworthy that the divergence dates within Collins and Dubach’s (2000b) inferred phylogeny all date to the late Pliocene or early Pleistocene, using the currently accepted age of 2.6 Ma for the boundary between these epochs.