One Long ArgumentPrimate and Human Evolution. By Susan Cachel. Cambridge: Cambridge University Press, 2006.

Abstract

The first sentence of the preface to this volume states, “This book is not intended to be an introductory textbook in physical anthropology.” Based on the title, this will come as a surprise to most readers. It also begs the question of why the first 50 pages include a potted history of physical anthropology. What is attempted here is to create a long argument for a particular (idiosyncratic, even) scenario for the emergence of hominins, one that explicitly ignores the bulk of scientific primatology. Cachel recognizes that this goes against the grain (“I am an apostate from primatology”; p. xv) but pursues the idea with a vigor that is commendable. The argument is summarized in chapter 16 (of 18), “Archeological Evidence and Models of Human Evolution.” It posits that a change in ancestral hominin sociality was the main trigger for differentiation from other apes; a reduction of intragroup competition encouraged food sharing, terrestriality, and natural history intelligence, which in turn created a cascade of anatomical and behavioral transformations of “hominization.” Indeed, Cachel tries to have it both ways in that she hypothesizes a reduction of competition in hominins but also argues that the high levels of competition seen in extant cercopithecoids are derived (p. 313). Nevertheless, the scenario represents a novel approach to the question of human adaptation and attempts to explain the unique features and adaptations of humans without resorting to environmental determinism. The remaining chapters range from “Primate Speciation and Extinction” (chap. 4) to “The Implications of Body Size for Evolutionary Ecology” (chap. 11), stopping along the way to criticize cladistics (Cachel uses an “anthropoid/prosimian” primate classification) and introduce robotic toy dogs. In retrospect, the object appears to have been to explain the author’s approach to the evidence in an attempt to build a long argument, but much of what is discussed is tangential, and the links between the material presented before chapter 16 and the model that forms the basis of the original contribution of the book are sketchy at best. For example, in chapter 3, a discussion of Teilhardina (an Eocene fossil primate) is justified in this way: “Because omomyids are tarsiiform primates, the fossil record of tarsiers is of interest to the study of early catarrhines” (p. 62). The impact of this statement, however, is lessened by the fact that she has already stated (p. 1) that, “I believe that tarsiers . . . have no special relation with higher primates”; to add to the sense of disconnectedness, this section is illustrated with a computer image of the cranium of Roonyia, an omomyid not mentioned in the text. Similarly, on page 11, Philip Herskovitz is criticized for creating subspecies on the basis of individual variations only to have those same distinctions cited as evidence for allopatric speciation in platyrrhines on page 87. There seems to be no attempt at all to integrate chapters 5 (“Anatomical Primatology”) and 6 (“Captive Studies of Nonhuman Primates”). The sense of disjointedness is spread throughout the work. A particular problem is with the illustrations. The cover image (of a pet spider monkey walking bipedally) is an example, as it is virtually a nonsequitur; it is taken from a short, marginally relevant chapter on captive primate studies, from a section called “Truly Aberrant Behaviors.” Many of the illustrations have been taken from other sources but have been digitally altered rather poorly. In addition, they seem to have been chosen haphazardly. The chapter titled “The Catarrhine Fossil Record” contains illustrations of (a) a specimen of a fossil cercopithecoid shown in situ (without accession number), (b) a photo of two living colobus monkeys, (c) a virtual 3-D reconstruction of a fossil omomyid, and (d) some giraffes. The real difficulty is working out who would benefit from such a work, as it seems to fall between several stools. Anyone expecting an introduction to primate (including human) evolution would have to look elsewhere, as the bulk of the fossil material is merely alluded to rather than being described in any detail. Much of the supporting material is only vaguely related to the main argument, but it is presented without sufficient detail and citation to justify its use as a review. There are undoubtedly some insights offered, but the revival of W. E. Le Gros Clark’s broad primate “trends,” the rejection of modern phylogenetic methods, and the dismissal of almost the whole of scientific primatology makes the book anachronistic at best. As a result, although the model of hominin origins advocated may prove to be fruitful, the long argument leading to it does not make a convincing case.