Hominoid dietary evolution

Abstract

During the later Palaeocene and early Miocene, catarrhine primates and the evolving hominoids had adaptations for frugivorous diets, with the emphasis on soft foods. Early in the middle Miocene the hominoids underwent a major shift, both in morphology and in habitat, with the morphology characterized by thickened enamel on the molars, enlarged incisors and massive jaws. The diet indicated by this morphology is interpreted as still mainly frugivorous but with changed emphasis, possibly towards harder objects. The thick-enamelled hominoids are found associated with more open forest habitats, and the distribution of food resources in equivalent habitats today is discontinuous both in time and in space, leading to evolutionary pressures particularly affecting locomotion, brain size and social behaviour. The earliest known hominid fossils differed little in dental and mandibular morphology from the middle Miocene apes, and the implied dietary similarity, together with ape-like patterns of dental development and retained arboreal adaptations of the postcrania, suggests little change in the foraging strategies of the earliest hominids compared with their ape ancestors and further suggests similarity in evolutionary grade. This similarity may have extended to other aspects of behaviour, for example to patterns of tool making and use, which may have been similar in the common ancestor of apes and humans to the pattern shared by the earliest australopithecines and chimpanzees.

A micro-CT based study of linear enamel thickness in the mesial cusp section of human molars: reevaluation of methodology and assessment of within-tooth, serial, and individual variation

“…(c) Left, horizontal section after the entire volume data set of (b) was rotated around a vertical axis so that protoconid and metaconid tips are aligned; right, vertical section running through both protoconid and metaconid EDJ tips, and an example of a thickness measure. (Andrews and Martin, 1991). In that case of an Ouranopithecus molar, the mesial-most section of Smith et al (2003), at an unstated distance from the initial section of Andrews and Martin (1991), exhibited a more salient EDJ cusp profile and a smaller enamel thickness value, indicating that the initially measured cross section was considerably off from the MCS.…”

“…(Andrews and Martin, 1991). In that case of an Ouranopithecus molar, the mesial-most section of Smith et al (2003), at an unstated distance from the initial section of Andrews and Martin (1991), exhibited a more salient EDJ cusp profile and a smaller enamel thickness value, indicating that the initially measured cross section was considerably off from the MCS. Similarly, we recently examined the measured block faces of an Australopithecus robustus molar sectioned by Grine and Martin (1988).…”

Variation in hominoid molar enamel thickness

“…Reported hominoid values from a controlled (physical) plane of section have necessarily been based on small sample sizes (Gantt, 1977;Martin, 1983Martin, , 1985Grine and Martin, 1988;Andrews and Martin, 1991;Macho, 1994;Beynon et al, 1998;Shellis et al, 1998;Grine, 2002;Olejniczak and Martin, 2002;Schwartz et al, 2003;Smith et al, 2003bSmith et al, , 2004Grine, 2005). Previous studies of extant ape molars have produced a maximum reported sample of 17 teeth from seven individuals of a single species (Martin, 1983).…”

Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

“…5,24,36,37 Finally, these results are considered in light of recent studies of enamel thickness within fossil and extant Homo sapiens, 35,[38][39][40] which are known to show a similar pattern of dental reduction over the same period. Given the significance of enamel thickness in assessments of hominoid systematics 28,29,32,35,41 and dental functional morphology, 33,34,42,43 characterization of enamel thickness within a geographically and temporally diverse hominoid genus will also permit more refined comparisons of limited samples of other fossil apes and humans.…”