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....