It is now well known that the concept of drifting continents became an estab­ lished theory during the 1960s. Not long after this "revolution in the earth sciences," researchers began applying the continental drift model to problems in historical biogeography. One such problem was the origin and dispersal of the New World monkeys, the Platyrrhini. Our interests in this subject began in the late 1960s on different conti­ nents quite independent of one another in the cities of Florence, Italy, and Berkeley, California. In Florence in 1968, A. B. Chiarelli, through stimulating discussions with R. von Koenigswald and B. de Boer, became intrigued with the possibility that a repositioning of the continents of Africa and South America in the early Cenozoic might alter previous traditional conceptions of a North American origin of the Platyrrhini. During the early 1970s this con­ cept was expanded and pursued by him through discussions with students while serving as visiting professor at the University of Toronto. By this time, publication of the Journal of Human Evolution was well underway, and Dr. Chiarelli as editor encouraged a dialogue emphasizing continental drift models of primate origins which culminated in a series of articles published in that journal during 1974-75. In early 1970, while attending the University of California at Berkeley, R. L. Ciochon was introduced to the concept of continental drift and plate tectonics and their concomitant applications to vertebrate evolution through talks with paleontologist W. A. Clemens and anthropologist S. L. Washburn.