Dimensional variation in the proximal ulna: evaluation of a metric method for sex assessment

The determination of sex is one of the fundamental assessments in the production of a biological profile for human skeletal remains, and a large number of studies have focused on evaluating sexual dimorphism metrically. A recent study of a contemporary American population presented high classification accuracies from discriminant function analysis of the proximal ulna (Grant and Jant,2003). The present research tests this method using a large sample (223 skeletons: 114 males and 109 females) from two skeletal assemblages of European origin, the documented Spitalfields Coffin-Plate Collection (N = 171) and the archaeological Raunds Furnells Collection (N = 52). The three measurements from the original study (Grant and Jant,2003), defined as the notch length (NL), the width of the olecranon process (OW), and the height of the coronoid process (CH) were tested, with the addition of a new variable radial notch height (RNH). Significant differences (P < 0.001) were found between male and female ulna measurements. Discriminant analysis found the original discriminant equation classified individuals with accuracies of only 40% for males but 99% for females. New discriminant functions were developed using direct and stepwise analyses of the Spitalfields sample. A direct multivariate function based on four dimensions (NL, OW, CH, RNH) produced an overall classification accuracy of 85.4% (males 82.4%; females 88.4%). A second function based on the original three measurements (NL, OW, CH) yielded nearly identical classification accuracies (males 81%; females 88.5%). Crossvalidation of the Spitalfields data using the three-variable function yielded an overall classification rate of 84.2%. This study indicates that the ulna is sexually dimorphic but its development is population-specific.