Global patterns of the cranial form of modern human populations described by analysis of a 3D surface homologous model

Abstract

This study assessed the regional diversity of the human cranial form by using geometric homologous models based on scanned data from 148 ethnic groups worldwide. This method adopted a template-fitting technique for a nonrigid transformation via the iterative closest point algorithm to generate the homologous meshes. Through the application of principal component analysis to 342 sampled homologous models, the largest variation was detected in overall size, and small South Asian crania were clearly verified. The next greatest diversity was found in the length/breadth proportion of the neurocranium, which showed the contrast between the elongated crania of Africans and the globular crania of Northeast Asians. Notably, this component was slightly correlated with the facial profile. Well-known facial features, such as the forward projection of the cheek among Northeast Asians and compaction of the European maxilla, were reconfirmed. These facial variations were highly correlated with the calvarial outline, particularly the degree of frontal and occipital inclines. An allometric pattern was detected in facial proportions in relation to overall cranial size; in larger crania, the facial profiles tend to be longer and narrower, as demonstrated among many American natives and Northeast Asians. Although our study did not include data on environmental variables that are likely to affect cranial morphology, such as climate or dietary conditions, the large datasets of homologous cranial models will be usefully available for seeking various attributions to phenotypic skeletal characteristics.

Cranial sexual dimorphism levels in modern humans: Supporting a global expansion originating in southern Africa

“…Similarly, if a cross-variable estimate (e.g., Cenac, 2023b) included cranial form dimorphism, then cranial form dimorphism would seem to complement support for southern Africa. However, cranial form is comprised of not only size but also shape (Matsumura et al, 2022), meaning that cranial form dimorphism would be redundant to cranial size and shape dimorphisms when estimating the origin. Given a general indication of a southern origin (Cenac, 2023b), finding the numerically highest coefficients to be in the south for cranial shape dimorphism does add some credence to the expansion being represented, to some level, in cranial shape dimorphism.…”

“…Is an increase in dimorphism with distance from Africa found when the dimorphism is of cranial shape or cranial form? Based on prior research (Cenac, 2022a(Cenac, , 2022b(Cenac, , 2023bHubbe et al, 2009;Kleisner et al, 2021;Matsumura et al, 2022;Messer et al, 2013), the answer might be yes.…”

“…A focus of the present study was on whether cranial form and cranial shape dimorphisms may be related to the global expansion. Size is a component of cranial form, as is shape (Matsumura et al, 2022), and cranial size dimorphism seems related to the expansion (Cenac, 2022b). Therefore, even if cranial form dimorphism is a product of the expansion, it would seem redundant as a measure of the expansion.…”

“…Cranial form has features of size and shape (e.g., Matsumura et al, 2022). Therefore, given that cranial size dimorphism elevates with geographical distance from Africa (Cenac, 2022b), and cranial shape dimorphism could possibly increase too, it would not be surprising if cranial form dimorphism increases with distance from Africa.…”

Variation, sexual dimorphism, and enlargement of the frontal sinus with age in adult South Africans

“…Another potential limitation to the comparison of frontal sinus volumes that have been recorded for different population samples arises from the variation in overall cranial size that may be evident between populations from different parts of the globe. For example, Matsumura et al (2022) assessed regional diversity in cranial form based on skulls from 148 ethnic groups worldwide and observed that the greatest variation detected was in overall size, with the second largest variation being in the length/breadth proportion of the neurocranium. This same caveat pertains to the examination of sexual dimorphism in frontal sinus size, since male and female crania tend to be dimorphic in overall size (e.g., Gonzalez et al, 2011; Toneva et al, 2022) in conjunction with differences in overall body size.…”