Comparative methods for studying primate adaptation and allometry

A well-known comparative biologist was once asked by a field biologist whet her the latter's detailed and painstaking field study of orangutan behavior , carried out over many years, qualified as an example of the comparative m ethod. "No," replied the comparative biologist, "that's an anecdote." The r eply is somewhat harsh, as useful comparisons can be conducted both within and across species. The reply does emphasize, however, that analysis of pat terns across species is fundamental to the study of adaptive evolution, par ticularly when variation needed to test hypotheses is present only at this interspecific level.(1-5) Examples in primatology include the occurrence of female sexual swellings in species with habitually multimale, rather than single-male, breeding systems,(6,7) the relationship between polygynandrous mating and relatively large testes size,(3 8) and the association between brain size and social group size.(9) Thus, in many cases, interspecific var iation is required to test adaptive hypotheses(10).