Patterns of tooth crown size and shape variation in great apes and humans and species recognition in the hominid fossil record

Abstract

It has been suggested that patterns of craniodental variation in living hominids (Gorilla, Homo, Pan, and Pongo) may be useful for evaluating variation in fossil hominid assemblages. Using this approach, a fossil sample exhibiting a pattern of variation that deviates from one shared among living taxa would be regarded as taxonomically heterogeneous. Here we examine patterns of tooth crown size and shape variation in great apes and humans to determine 1) if these taxa share a pattern of dental variation, and 2) if such a pattern can reliably discriminate between samples that contain single species and those that contain multiple species. We use parametric and nonparametric correlation methods to establish the degree of pattern similarity among taxa, and randomization tests to assess their statistical significance. The results of this study show that extant hominids do not share a pattern of dental size variation, and thus these taxa cannot be used to generate expectations for patterns of size variation in fossil hominid species. The hominines (Gorilla, Homo, and Pan) do share a pattern of shape variation in the mandibular dentition; however, Pongo is distinct, and thus it is unclear which, if either, pattern should be expected in fossil hominids. Moreover, in this case, most combined-species samples exhibit patterns of shape variation that are similar to those for single hominine species samples. Thus, although a common pattern of shape variation is present in the mandibular dentition, it is not useful for recognizing taxonomically mixed paleontological samples.

A dental topographic analysis of chimpanzees

“…Tooth shape in particular has been found to be related to the mechanical properties of foods eaten (Lucas, 2004). Morphological differences can also be used to infer phylogenetic distance between taxa (Plavcan, 1993;Uchida, 1996;Plavcan and Cope, 2002;Scott and Lockwood, 2004;Pilbrow, 2007). Morphological differences can also be used to infer phylogenetic distance between taxa (Plavcan, 1993;Uchida, 1996;Plavcan and Cope, 2002;Scott and Lockwood, 2004;Pilbrow, 2007).…”

Genetic and environmental contributions to variation in baboon cranial morphology

“…Questions of character selection and definition are often approached by testing hypotheses about the intrinsic variational properties of characteristics, which are hypothesized to influence the evolutionary potential of characteristics such that they differentially reflect phylogenetic relationships among species (Lieberman, 1995; Lieberman et al, 1996; Collard and Wood, 2001, 2007; Wood and Lieberman, 2001; Lycett and Collard, 2005). The roles of development and constraints, because of integration among traits along with the possibility that different traits are exposed to different environmental stimuli, have also been an important focus of recent research into the variational and evolutionary properties of skeletal morphology (Lieberman, 1995; Lieberman et al, 1996, 2000a,b; Lockwood and Fleagle, 1999; Collard and Wood, 2001, 2007; Ponce de Leon and Zolikoffer, 2001; Wood and Lieberman, 2001; Lockwood et al, 2004; Scott and Lockwood, 2004; Lycett and Collard, 2005; Lockwood, 2007; Smith et al, 2007). By using a model organism (the baboon) from a population of known pedigree, we are able to partition phenotypic variation into genetic and environmental components to test hypotheses about whether these criteria for selecting characteristics for phylogenetic analysis predict the patterns of phenotypic, genetic, and environmental variation that interact with the forces of evolution to produce differences between species.…”

Microbial osteolysis in an Early Pleistocene hominin (Paranthropus robustus) from Swartkrans, South Africa

“…Similarly, Thackeray et al (2005) have opined that because the MD/BL crown shape indices of some of the smaller P. robustus M 1 sdincluding SKX 5013doverlap those of early Homo specimens, the former may represent males of the latter. However, pronouncements based on a single metric in which there is demonstrable overlap among species ranges are of little taxonomic utility (Scott and Lockwood, 2004; see also Gordon and Wood, 2013). Grine et al (2012) have suggested a gorilla-like level of dimorphism in P. robustus on the basis of mandibular molar crown dimensions.…”