INTRODUCTION

Darwin first wrote about sexual selection in 1871, but only since the 1970s has it become a topic of intense scientific study. The Göttinger Freilandtage (conference) on sexual selection in primates which resulted in this chapter, was held exactly 125 years after Darwin first published his paper on sexual selection on visual signals in primates (1876). How far have we come in understanding sexual selection of communication signals since Darwin's first introduction of the topic? We have had considerable advances in studying sexually selected vocalisations in anurans (e.g. Ryan & Rand, 1990) and birds (e.g. Searcy & Andersson, 1986); sexually selected visual traits in birds (e.g. Borgia, 1985; Petrie, 1994) and invertebrates (e.g. Wilkinson & Reillo, 1994); as well as chemical signals in invertebrates (e.g. Eisner & Meinwald, 1995). The major focus of most of these studies has been on variation in male traits that provide a basis for female choice.

As I have surveyed the primate literature relating communication signals to sexual selection, my assessment is that we have very little real understanding of the role of sexual selection on primate communication that is comparable to our knowledge of other taxa. I think there are several reasons for this lack of progress since Darwin. First, primatologists have lost track of the steps needed for a truly scientific validation of sexual selection, which often requires controlled experimentation. A clear understanding of sexual selection requires not only attempting to understand ultimate causes, but also close attention to proximate mechanisms.