It is perhaps widely appreciated in the realm of primatology that until fairly recently, our perspective on gorillas has been an unbalanced one. Our earliest and most comprehensive accounts of gorillas in the wild can be traced almost entirely to studies of the East African gorillas of the Virunga mountains, Gorilla gorilla beringei or, as it is now being called by some, Gorilla beringei beringei, even though explorers' initial contacts were with the gorillas of West Africa. This is not unlike our early view of the chimpanzee, which for the better half of the twentieth century was based primarily on the chimpanzees of Gombe and the work of Jane Goodall, or our early view of the orangutan, which for years was informed by work conducted at only a few sites along the Bornean coast.

Pioneering work by well known field primatologists, such as George Schaller and Dian Fossey, provided the first systematic accounts of gorillas, cementing in our minds the image of these animals as plant-eating, quadrupedal, terrestrial knuckle-walkers. As a testimonial to the one-sided nature of these early gorilla field studies, the first important attempt to document the behavior of the western lowland gorilla is briefly noted by Schaller in the Preface to the Phoenix Edition of his landmark study The Mountain Gorilla, as “an interesting report on the little-known West African gorilla”.

Introduction

The classic studies of Coolidge (1929) and Groves (1967, 1970a, b, 1986; Groves and Stott, 1979), coupled with more recent investigations (Uchida, 1996, 1998; Taylor, 1998a, b, 1999, 2002), have revealed considerable variability in the cranium, mandible, and dentition among subspecies and even geographic populations of gorillas (Albrecht et al., Leigh et al., Stumpf et al., this volume). Historically, investigators have tended to emphasize the taxonomic implications of this variation (Coolidge, 1929; Groves, 1967, 1970a) and with good reason, as a well-founded taxonomy clearly forms the basis for meaningful studies in other important fields, including morphology, behavioral ecology, and genetics. While there have been some attempts to draw functional inferences from differences in craniomandibular and dental morphology among gorilla subspecies (Vogel, 1961; Groves, 1970a, b; Uchida, 1996, 1998; Taylor, 1998b, 1999, 2000), nevertheless the nature and patterning of variation in jaw form among gorilla subspecies remains unresolved.

I examine masticatory form and function in gorillas to assess whether gorilla subspecies differ predictably in morphology as a function of dietary specialization. I focus particularly on the expected pattern of morphological differentiation in Gorilla based on the degree to which these taxa differ in degree of folivory versus frugivory. I use an ontogenetic, allometric approach in an explicitly phylogenetic context to evaluate whether differences among subspecies can be principally attributed to extrapolation or truncation of inherited patterns of ontogenetic allometry (Shea, 1995), or to derived dissociations of ancestral allometries.

Once, in the Central African Republic, a BaAka pygmy working with one of us (MLG) left a “precious” pack of matches on a log near a nesting site. “Wanga, you left your matches behind.” His response, “The gorillas have been without fire for too long – it is not fair.” The human-like quality of gorillas is one reason we are compelled to study them. By examining all aspects of their biology, we begin to understand them and, in so doing, gain insight into ourselves.

In this multidisciplinary approach to gorilla biology, the contributing authors have advanced our knowledge of these apes. Some have yielded novel insights, while others have provided greater clarity with more detailed and comprehensive analyses. Yet, with each insight, additional questions are generated, and challenges remain.

As has been pointed out by several contributors, though the use of molecular genetics to address questions of phylogeny and taxonomy is not new, we are still in the formative stages in terms of our ability to interpret genetic variation from molecular data and draw biologically meaningful distinctions. This is reflected in the fact that debates over gorilla taxonomy, as presented both here and elsewhere, center at least as much on methods as on findings. One need only compare the results and interpretations of molecular studies that rely on different (and sometimes even identical!) genetic markers to see that this is so.

Which genetic markers are phylogenetically informative? What sample sizes are needed to achieve reliable results?