Ann H. Ross, 1 M.A.; Richard L. Jantz, 1 Ph.D.; and William F. McCormick, 2 M.D. Cranial Thickness in American Females and Males REFERENCE: Ross AH, Jantz RL, McCormick WF. Cranial Materials and Methods thickness in American females and males. J Forensic Sci 1998; 43(2):267–272. Sample The sample was 165 autopsied specimens collected by William ABSTRACT: To date, numerous studies have examined the range F. McCormick, M.D., Deputy Chief Medical Examiner, State of of cranial thickness variation in modern humans. The purpose of this investigation is to present a new method that would be easier Tennessee, and 15 specimens from the William M. Bass Donated to replicate, and to examine sex and age variation in cranial thick- Collection curated at the University of Tennessee, Knoxville ness in a white sample. The method consists of excising four cranial (Table 1). The sample consists of 58 females and 122 males. Of segments from the frontal and parietal regions. The sample consists these, 144 consist of cranial sections collected at autopsy, and 36 of 165 specimens collected at autopsy and 15 calvarial specimens. An increase in cranial thickness with age was observed. The consist of autopsied calvaria. The criteria for inclusion were known results suggest that cranial thickness is not sexually dimorphic out- age, sex, and race. Manner of death was either by accident, suicide, side the onset of hyperostosis frontalis interna (HFI). homicide, or natural causes. Hyperostosis frontalis interna was diagnosed as an obvious overgrowth of compact (cortical) bone KEYWORDS: forensic science, cranial thickness, hyperostosis on the inner table that is generally quite focal and localized to the frontalis interna, forensic anthropology frontal region but occasionally involves the parietal bones without stigmata of Paget’s disease. Cranial thickness has been used to investigate differences between ethnic groups, to account for sexual dimorphism, to Measurements expound the phylogenetic relationships of Homo, and even to infer The general locations of the parietal and frontal eminences were behavioral differences (e.g., activity levels). Lieberman proposed selected for thickness measurements because they are considered that exercise and the levels of growth hormone (GH) released dur- to be least affected by structural variations such as ectocranial ing exercise, not genetics, accounted for most of the variation muscle attachment sites and sinuses (16). Four cranial sections observed among hunter-gatherers, early agriculturalists, and post- were excised at autopsy from the frontal and parietals (Fig. 1). The industrial Homo sapiens (1). Gauld, however, maintained that vari- bilateral site of excision on the parietal bones is four centimeters ance in vault bone thickness is explained by body size variation postero-laterally from bregma, and four centimeters antero-lat- (2). erally from bregma on the frontal bone. Cranial sections were Todd (3) and Getz (4) concluded that cranial thickness increased removed with a Stryker saw. Measurements on the calvaria were slightly with age. Adeloye and coworkers observed a rapid increase taken at the sites of excision defined above, yielding four thickness in cranial thickness in the first two decades and a gradual increase dimensions per specimen: right and left parietal and right and left in the third-to-seventh decade of life (5). They also observed that in frontal (lp, rp, lf, rf) (refer to Fig. 1). The measurements were taken certain age groups females had significantly thicker cranial bones, with Mitutoyo dial calipers to the nearest tenth of a millimeter. although the sex differences were quite variable and dependent upon cranial location (5). The higher incidence of hyperostosis Statistics frontalis interna (HFI) or marked thickening of the endocranial surface of the frontal bone, among post-menopausal females could Standard summary statistics of the four thickness variables and explain this increase in thickness in older females (6,7). However, age were calculated, including means, standard deviations, and there are almost as many studies that contradict these findings intercorrelations. A two-sample t-test was also conducted to deter- (8–11), studies which found no significant difference in cranial mine whether significant differences in group means between thickness with increased age. Similarly, investigations of sexual females and males were present. An approximate two-sample t- dimorphism also yielded inconclusive results (12–15). This incon- test was obtained for the variables rp, lf, and rf due to unequal sistency could be a product of both small sample size and different methodologies used. The purpose of this investigation is twofold: 1) to introduce a TABLE 1—Summary of sample (N 4 180).* simple, easy to replicate method; and 2) to examine sex and age variation in a white sample. Calvaria Sections Total 1 The University of Tennessee, Department of Anthropology, 252 S. Females 7 51 58 Stadium Hall, Knoxville, TN. Males 29 93 122 2 East Tennessee State University, Department of Forensic Pathology, Box 70425, Johnson City, TN. *Samples were obtained from the Regional Forensic Center, Johnson City, TN (N 4 165), and the Donated Collection, University of Tennessee, Received 28 March 1997; and in revised form 1 July, 22 July 1997; accepted 4 Aug. 1997. Knoxville, TN (N 4 15). 267 Copyright © 1998 by ASTM International www.astm.org Copyright by ASTM Int'l (all rights reserved); Thu Feb 9 14:21:07 EST 2017 Downloaded/printed by (UFPR) Universidade Federal do Parana ((UFPR) Universidade Federal do Parana) pursuant to License Agreement. No further reproductions authorized.