Sexual dimorphism in the Japanese cranial base: A Fourier‐wavelet representation

Abstract

An approach, computational shape analysis (CSA), is presented here which utilizes a Fourier-wavelet representation to numerically describe shape features of biological forms. Two elements are involved: 1) elliptical Fourier functions (EFFs), to provide estimates of global aspects, and 2) continuous wavelet transforms (CWTs) to generate an objective estimate of localized features. EFFs are computed, using a set of pseudohomologous points, to create a precise analog of the boundary. This computed contour is then normalized by scaling and rotated in two-dimensional space to insure a representation that is invariant with respect to starting point, size, and orientation. The predicted point coordinates derived from the EFFs are submitted to CWT for further processing. Wavelet coefficients are then computed to identify localized features, localization being a subjective process with EFFs. The advantage of wavelets is that they eliminate the inevitable subjectivity inherent in the choice of measurements. To test the usefulness of CSA, a sample of cranial base (CB) lateral radiographic outlines was available. Five archaeological periods, Yayoi, Kofun, Kamakura, Edo, and Modern, were utilized (n = 297). Statistically significant differences in sex and archaeological age were found. Although archaeological age differences were present, they were small and random in character, suggesting stability in the CB structures. In contrast, sexually dimorphic differences were present in every group from the Yayoi to the Modern period. This presence of sexually dimorphic differences in shape was consistent with earlier studies of M. nemestrina, G. gorilla, and P. troglodytes. Consequently, it is suggested that the pattern of sexual dimorphism documented in the Japanese CB is a primate pattern with an ancient evolutionary history. The results demonstrate, both visually and numerically, that CSA is a powerful approach for describing both global and localized features of craniofacial structures such as the CB.

Sexual dimorphism using elliptical Fourier analysis: shape differences in the craniofacial complex

“…Results based on the M. nemestrina cranial base prompted further studies using human data to see if a similar pattern of sexual dimorphism could be discerned (Lestrel et al, 2004a(Lestrel et al, , 2005). An early initial longitudinal study using conventional Fourier analysis hinted at cranial base shape differences due to sex, but these shape changes, while present, were not recognized or followed up at the time (Lestrel and Roche, 1986).…”

“…Thus, while Fourier coefficients or their amplitudes are useful for capturing the global aspects of a form, the localization or identification of local aspects is not readily possible. A method that has been recently developed to circumvent this constraint and will recognize any changes in curvature, are wavelets (see Lestrel et al, 2004aLestrel et al, , 2005 for an extended discussion of these issues).…”

Wavelet analysis of ammonoid sutures

“…wavelet transform was first used as a morphometric tool to characterize localized changes in a closed outline of organic form (Takemura et al, 2004;Lestrel et al, 2005). Lestrel et al (2005) used a series of coordinate data along the outline curve as a descriptor function instead of a time series data.…”

“…Lestrel et al (2005) used a series of coordinate data along the outline curve as a descriptor function instead of a time series data.…”

Sexual Dimorphism Determination from the Lineal Dimensions of Skulls

“…It is possible to determine sex from isolated bony pieces such as the temporary bone, frontal, in jaw, in orbit, and in tooth of the skull by studying a group of traditional morphological indicators or through the calculation of general cranial dimensions and the angles formed among craniometric points (Baughan & Demirjian, 1978, Lestrel et al, 2005Ursi et al, 1993;Olivier & Tissier, 1977;Bibby, 1979;Kalmey & Rathbun, 1996;de Paiva & Segre, 2003;Kemkes & Gobel, 2006;Celbis et al, 2001;Wescott & Moore-Jansen, 2001;Panella et al, 1988;Buschang et al, 1986;Rosas et al, 2002;Steyn & Iscan, 1998;Franklin et al, 2007;Schmittbuhl et al, 2001;Loth & Henneberg, 1998;Loth & Henneberg, 1996;Balci et al, 2005;Haun, 2000;Lam et al, 1996;Graw et al, 1999;Schleyer et al, 1971;Introna et al, 1993;Kondo et al, 2005;Abdelmalek & Michael, 1984).…”