Allometry and heterochrony in the African apes

Abstract

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.

Multivariate Cranial Ontogenetic Allometries in Crab-eating, Rhesus and Japanese Macaques.

“…M. fascicularis attains the adult level of dimorphism earlier, at dental age 6, than M. mulatta, which show a low level of dimorphism similar to that of M. fuscata at dental ages 5 through 7. This finding indicates a higher level of rate hypermorphosis (Shea, 1983) in males relative to females for M. fascicularis. The situation of M. mulatta seems to be brought about either by a higher level of time hypermorphosis or by a late but strong rate hypermorphosis in males relative to females.…”

A geometric morphometric analysis of heterochrony in the cranium of chimpanzees and bonobos

“…These studies differ from that of Shea (1983a) by describing shape as ratios of interlandmark distances and using size measurements that are intrinsic to the skull. When interlandmark distances are compared, mainly using basicranial length and palate length to represent the growth regions of the neurocranium and face, respectively, there is strong evidence for ontogenetic scaling between these measurements (Shea 1983b(Shea , 1984(Shea , 1985(Shea , 1992, implying that the bonobo is paedomorphic through hypomorphosis (or progenesis). When shape is defined as the ratio between basicranial length and palate length, and basicranial length is used as a proxy for size, then the bonobo is reduced in size and juvenalized in shape compared to the chimpanzee at the end of development, but size and shape are not dissociated from each other (Alba, 2002).…”

Common patterns of facial ontogeny in the hominid lineage

“…Our results support those findings and suggest that common facial developmental patterns extend further back in evolutionary time (to include the type species of Australopithecus), ontogenetic time (to include younger juveniles), and more broadly among living primates (to include Pan paniscus). It is not surprising that similar juvenile developmental patterns exist among great apes (Shea, 1983) or among later members of the genus Homo (Krovitz, 2000;Ponce de Leó n and Zollikofer, 2001), given each groups' close morphological resemblance and phylogenetic relationship. What is surprising is that a shared pattern of juvenile facial development is more widespread among the hominoids, possibly representing either the primitive condition for the African great ape/human clade, from which gorillas diverged, or the derived condition of the Pan/human clade.…”

“…It is well accepted that small changes in the rate or timing of developmental events can provide a mechanism for evolutionary change by generating morphological differences between species (Gould, 1977;Shea, 1983Shea, , 1989Hall, 1984;Godfrey and Sutherland, 1996). Analyses of several juvenile fossil hominid crania and dentition indicate that their development is fast relative to that of modern humans; this is true for australopithecines and early Homo (Smith, 1986(Smith, , 1991Beynon and Wood, 1987;Bromage, 1987;Conroy and Vannier, 1987), as well as the more temporally recent Neanderthals (Dean et al, 1986;Stringer et al, 1990).…”