Sex determination by discriminant analysis using roentgenographic cephalometric data and its application to Yin-Shang skulls

Abstract

Recently, the authors investigated skulls from the Yin-Shang period, a great collection of the Institute of History and Philology, Academia Sinica, the Republic of China (Taiwan). Their roentgenographic cephalograms were taken of two hundred thirty eight well preserved skulls. In analyzing these x-ray pictures, however, a difficult problem occurred in judging the sex of each individual, because no method had been developed before for this purpose. In this study, therefore, it was attempted to develop a method for evaluating the sex of individuals through roentgenographic cephalometrics.
As the first step of the study, 45 skulls of the recent Atayals, in which the sex of each individual was recorded, were used as materials for devising the method of analysis. Glabella and mastoid were adopted as objects of measurement, and nine measuring items were established as shown in Table 2 and Fig. 2. Using a discriminant function which was created from only three variables, namely MaHT, GMPN, and GMFH, from 41 individuals with no missing value, the total cases of 45 individuals were classified into two sexual groups with 93.30% correct.
The second step of the study was to apply the newly designed method to six skeletal populations from the Yin-Shang period, of which individuals were classified into three groups of male, female, and sex uncertain, according to YOUNG (1985a). Using discriminant functions which were created from the data obtained from the male and female skulls, the uncertain individuals were divided into two groups of male and female, though the reliability of a few cases were less than 0.7.
From these results, the items and the method of measurement seemed to work as favourably as the traditional method of sex determination by direct observation of skulls. Another merit of this method is easiness of measurement on a twodimensional plane in comparison with a direct measuring method on actual skulls. Putting all the findings together, the roentgenographic cephalometric method used in the present study is effective enough for sex discrimination.