This analysis investigates the ontogeny of body size dimorphism in apes. The processes that lead to adult body size dimorphism are illustrated and described. Potential covariation between ontogenetic processes and socioecological variables is evaluated. Mixed-longitudinal growth data from 395 captive individuals (representing Hylobates lar [gibbon], Hylobates syndactylus [siamang], Pongo pygmaeus [orangutan], Gorilla gorilla [gorilla], Pan paniscus [pygmy chimpanzee], and Pan troglodytes ["common" chimpanzee]) form the basis of this study.Results illustrate heterogeneity in the growth processes that produce ape dimorphism. Hylobatids show no sexual differentiation in body weight growth. Adult body size dimorphism in Pongo can be largely attributed to indeterminate male growth. Dimorphism in African apes is produced by two different ontogenetic processes. Both pygmy chimpanzees (Pan paniscus) and gorillas (Gorilla gorilla) become dimorphic primarily through bimaturism (sex differences in duration of growth). In contrast, sex differences in rate of growth account for the majority of dimorphism in common chimpanzees (Pan troglodytes).Diversity in the ontogenetic pathways that produce adult body size dimorphism may be related to multiple evolutionary causes of dimorphism. The lack of sex differences in hylobatid growth is consistent with a monogamous social organization. Adult dimorphism in Pongo can be attributed to sexual selection for indeterminate male growth. Interpretation of dimorphism in African apes is complicated because factors that influence female ontogeny have a substantial effect on the resultant adult dimorphism. Sexual selection for prolonged male growth in gorillas may also increase bimaturism relative to common chimpanzees. Variation in female growth is hypothesized to covary with foraging adaptations and with differences in female competition that result from these foraging adaptations. Variation in male growth probably corresponds to variation in level of sexual selection. 0 1995 Wiley-Liss, Inc.

In this work allometry and heterochrony are integrated in an analysis of ontogenic and interspecific morphological patterns in the African apes. The relationship between the interspecific differences in adult morphology and the differences in underlying patterns of growth allometries, body weight growth rates, and developmental chronologies is investigated. Results indicate that rate hypermorphosis, or the extension of ancestral allometries into new size/shape ranges with no increase in the duration of ontogeny, underlies many of the interspecific differences in form among the African apes. In addition, the need for further clarification of the processes of heterochrony is stressed by distinguishing between rate and timing differences. These distinctions and processes are illustrated and discussed using the morphological data on the African apes.

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A determination of the capacity of the maxillary sinus was made for eight Eskimo populations, one Mongolian population and one American white population. Statistical analyses reveal strong and significant correlations of the mean temperature of the coldest month where these populations live with differences in mean maxillary sinus volume (MSV) values. Results indicate that maxillary sinus volume in Eskimo populations decreases in colder areas. These changes may be due to commensurate structural ramifications of internal nasal anatomy variation, specifically of the inferior concha (maxilloturbinal) and inferior meatus. A review of the physiological, morphological and cultural responses of the Eskimo to cold suggests that only the facial area as a whole, and the internal nasal apparatus in particular, sustain significant cold exposure. The "cold-engineered" hypothesis of Mongoloid craniofacial form (Coon et al., '50) finds little support in the anthropological research and literature.

Examination of relative growth and allometry is important for our understanding of the African apes, as they represent a closely related group of species of increasing body size. This study presents a comparison of ontogenetic relative growth patterns of some postcranial dimensions in Pan paniscus, Pan troglodytes, and Gorilla gorilla. Interspecific proportion differences among the three species are also analyzed. It is stressed that reliable ontogenetic information can only be obtained if subadults are examined-growth data cannot be inferred from static adult scaling. Results indicate that some postcranial relative growth patterns are very similar in the three species, suggesting differential extrapolation of a common growth pattern, whereas for other proportion comparisons the growth trends differ markedly among the species, producing distinct shape differences in the adults. Interspecific shape changes among the three species are characterized by positive allometry of chest girth and negative allometry of body height and leg length. It is suggested that relative decrease of leg length with increasing body size among the African pongids might be expected on biomechanical grounds, in quadrupedal terrestrialism. Relative to body weight or trunk length, the limbs of the bonobo (Pan paniscus) are longer than in the common chimpanzee or the gorilla, with a lower intermembral index. This may most closely resemble the primitive condition for the African apes.

This paper reviews the evidence for the claim that neoteny, or morphological juvenilization resulting from dissociation and retardation of ancestral rates of shape change, has played a key role in human evolution. Accepted categories and processes of heterochrony are reviewed, and the available data on human growth, variation, and evolution are analyzed in light of expected results. Relatively weak concordance with predictions is found. Mistakes of fact and interpretation fall into several categories, including 1) confusion of neoteny with paedomorphosis resulting from other heterochronic processes; 2) conflation of growth prolongation in time with morphological shape retardation; 3) failure to move beyond superficial shape similarities to underlying homologous growth processes and patterns; 4) failure to identify a paedomorphic basis for key anatomical novelties in human evolution; and 5) establishing an essentially untestable framework for analysis of the hypothesis. Key areas that might contribute new data to this debate are discussed, particularly the genetic and epigenetic control of the covariation of morphology and development during ontogeny and evolution. The primary reasons that arguments in favor of neoteny in human evolution have persisted probably relate to anthropocentric factors and the search for a single basis for the important morphological and behavioral transformations characterizing our lineage.The claim that neoteny has played a central role in human evolution has spawned one of the most persistent and vexing debates in physical anthropology over the past century. Treatments ranging from focused morphological investigations to major theoretical treatises have been produced, but little in the way of consensus and resolution has emerged. How, therefore, can we justify yet another review of this problem? I attempt such a justification along several lines. First, the volume of ink spilled over this topic is hardly evenly divided between pro and con-advocates outnumber detractors, at least in the published literature of the past several decades. I will argue here that there are numerous inconsistencies in these arguments that have never been pointed out, sufficiently stressed, or synthesized. Second, there is a considerable amount of new information germane to this issue that has been produced in the decade since the last major review of human neoteny, that by Gould (1977). Most of this information comes from outside the study of human evolution, but it is directly relevant to the question of human neoteny nonetheless. Finally, rather than simply attempting to offer a resolution or the "final word" on this topic, I will try to point out the areas of critical knowledge that are lacking and that would contribute to a better understanding of this and related issues. Because most previous authors have strongly and defensively 0 1989 Alan R. Liss, Inc. YEARBOOK OF PHYSICAL ANTHROPOLOGY[Vol. 32, 1989 advocated a particular view in this debate, there has been relatively little consideration...

Size variation in African apes (Gorilla gorilla [gorilla], Pan paniscus [pygmy chimpanzee], and Pan troglodytes ["common" chimpanzee]) is substantial, both within and between species. We investigate the possible evolutionary significance of this variation through an analysis of the ontogeny of size variation in this group. In addition, we highlight possible areas of future endocrinological research, and evaluate recently proposed alternative models that attempt to account for ontogenetic variation in apes. The present study shows that intergeneric variation in size is largely a consequence of differences among species in the rate of body weight growth. Interspecific size variation in Pan is a product of both rate and duration differences in growth. The ontogenetic bases of sexual dimorphism vary in this group. Dimorphism is largely a result of sex differences in the duration of body weight growth in gorillas and pygmy chimpanzees, but results from differences in the rate of growth in common chimpanzees. Ontogenetic analyses largely confirm earlier interpretations, but with better data and methods. The great degree of ontogenetic variation within and among these species, especially in the timing and magnitude of "pubertal" growth spurts, implies that studies of endocrine growth control in African apes could be a productive line of future research. We also suggest that ontogenetic variation can be understood with respect to ecological risks. Growth rates seem to be negatively correlated with ecological risk in African apes, suggesting links between ontogenetic patterns and social and ecological variables. High growth rates in gorillas compared to Pan are most consistent with this model. Variation between chimpanzees and pygmy chimpanzees (especially females) also seem to fit predictions of this model.

The study of hominoid phylogeny is currently in a state of controversy and debate due to the discovery of new fossil material and reanalysis of the morphology of extant apes. An important key to the resolution of these debates lies in attaining a fuller understanding of the morphological differences in skull form between the African and Asian great apes. In this paper I have analyzed aspects of facial morphology and internal cranial anatomy in the great apes. Results from this study and previous ones suggest that Pongo is characterized by a marked dorsal deflection of the face relative to the basicranium. Many aspects of circumorbital, midfacial, palatal, and mandibular morphology in Pongo may be related to this airorynchous condition. This hypothesis is supported by Enlow's work on form and pattern in the primate and mammalian skull. The position of the face in known Sivapithecus appears to be similar to that seen in Pongo. Although Pongo may be specialized in its marked degree of airorynchy, it seems likely that an important derived feature linking African apes and hominids is a ventral rotation of the splanchnocranium on the neurocranium. The appearance of marked supraorbital tori and ethmofrontal sinuses are probably correlated developments. Additional implications of this work for debates about hominoid phylogeny are discussed.