ABSTRACT
Knowledge about nonhuman primate behavior expanded rapidly through the 1960s as socioecolological research on a large number of previously unstudied species was published. Much of this research pointed to impressive complexity in monkey and ape societies with clear, but complex, implications for understanding human evolution and behavior. Strikingly, however, one prominent aspect of nonhuman primate (hereafter, primate) behavior, vocal communication, was not thought to be very intricate or sophisticated. Primatologist Jane Lancaster (1968) summarized the prevalent view by noting,
