Geometric Morphometrics in Primatology: Craniofacial Variation in Homo sapiens and Pan troglodytes

Abstract

Traditionally, morphometric studies have relied on statistical analysis of distances, angles or ratios to investigate morphometric variation among taxa. Recently, geometric techniques have been developed for the direct analysis of landmark data. In this paper, we offer a summary (with examples) of three of these newer techniques, namely shape coordinate, thin-plate spline and relative warp analyses. Shape coordinate analysis detected significant craniofacial variation between 4 modern human populations, with African and Australian Aboriginal specimens being relatively prognathous compared with their Eurasian counterparts. In addition, the Australian specimens exhibited greater basicranial flexion than all other samples. The observed relationships between size and craniofacial shape were weak. The decomposition of shape variation into affine and non-affine components is illustrated via a thin-plate spline analysis of Homo and Pan cranial landmarks. We note differences between Homo and Pan in the degree of prognathism and basicranial flexion and the position and orientation of the foramen magnum. We compare these results with previous studies of these features in higher primates and discuss the utility of geometric morphometrics as a tool in primatology and physical anthropology. We conclude that many studies of morphological variation, both within and between taxa, would benefit from the graphical nature of these techniques.

Ontogenetic and static allometry in the human face: Contrasting Khoisan and Inuit

“…Our result support earlier studies (e.g., Howells, 1973Howells, , 1989Hennessy and Stringer, 2002;Hanihara, 2000) by showing that the Inuit differ from other regional groups mainly in their facial flatness (Howells, 1973(Howells, , 1989Hennessy and Stringer, 2002); the SW Amerindian group has a more robust and transversely projecting zygomatic region (Hanihara, 2000); Austria/France have narrower faces, retracted zygomatic bones, projecting nasal bones and vertical frontal bones (Howells, 1973(Howells, , 1989Luboga and Wood, 1990;Lynch et al, 1996;Hanihara, 2000;Hennessy and Stringer, 2002); and the Khoisan have smaller facial breadths and heights combined with broad nasal apertures (Howells, 1973), as well as an angled (anteroinferiorly) infraorbital region and projecting zygomatic bones.…”

Differences between sliding semi‐landmark methods in geometric morphometrics, with an application to human craniofacial and dental variation

“…Although several studies have found differences in the results achieved by traditional and landmark-based morphometric methods (Adams & Funk, 1997;Monteiro & Abe, 1999;Monteiro-Filho et al 2002;Reis et al 2002), other examples show that linear and landmark-based descriptors appear to be effective at capturing major shape features and describing intergroup differentiation (Lynch et al 1996;Navarro et al 2004). Accordingly, the effect of methods on results seems to be related to the type of analysis performed and the amount of within-and between-group variation (Navarro et al 2004).…”

“…Concurrently, there is a considerable amount of empirical evidence demonstrating the ability of landmark-based geometric methods to provide new insights into patterns of biological shape variation that could not be evaluated by traditional methods (Monteiro & Abe, 1999;Reis et al 2002; among others; cf. Lynch et al 1996). For example, in some studies geometric morphometrics methods were able to discriminate groups (e.g.…”

A crossbeam co-ordinate caliper for the morphometric analysis of lithic nuclei: a description, test and empirical examples of application

“…However, since the seminal work of Bordes [6], Roe [48,49] and Isaac [23] there has been surprisingly little advance in the quantitative morphometric analysis of such artefacts, especially compared to that which has taken place in biological morphometrics (e.g. [4,5,20,29,42,43,67]). Others [2,53] have suggested that quantitative techniques of shape analysis employed in biology have moved on to such a great extent in recent decades, that a veritable 'revolution' has taken place.…”