Plate tectonics and the problem of anthropoid origins

Using plate tectonic theory, geologic and geophysical determinants of South Atlantic opening are assessed during the Cretaceous through the Oligocene (approximately 135–25 m.y.B.P.). This is done to evalute the feasibility of statements on paleontologic and neontologic distributional data that relate to African and South American separation as the South Atlantic was created. In particular, the question of anthropoid origins is examined in light of plate tectonic theory, and the idea that monophyly of the anthropoid grade is supported by continental drift is refuted. When geological and geophysical evidence is examined in detail, the occurrence of Tertiary transfer of primates between Africa and South America is improbable. Thus one must look to either North America or Middle America for the ancestors of the platyrrhines, and to Eurasia for the ancestors of the catarrhines. The problem of whether those ancestors were prosimians or anthropoids is not dealt with, because the question of whether the Platyrrhini and the Catarrhini are independently evolved from prosimian ancestors (anthropoid diphyly) or are evolved from ancestors that were already of an anthropoid level of structural organization (anthropoid monophyly) can only be resolved on biological grounds and at a level of analysis that allows one to distinguish between analogies developed in parallel, homologies caused by symple-siomorphy, and homologies caused by synapomorphy.