Identifying artificially deformed crania

Abstract

In this paper we report on a new discriminant function for the identification of artificially deformed crania. Development of the function, based on a sample of deformed and undeformed crania from the Philippines, required visual classification of the sample into deformed and undeformed groups. Working from the observation that deformed crania display flattened frontal and occipital regions, the sample was seriated based on degree of flattening; classification was based on the results of this seriation. The discriminant function, calculated using curvature indices, required only six simple measurements: arc and chord measurements for the frontal (glabella to bregma), parietals (bregma to lambda) and occipital (lambda to opisthion). The function was designed to be conservative, in that a deformed cranium may be classified as undeformed, but the opposite should not occur. Our function classified the undeformed crania with 100% accuracy and deformed crania with 76.9% accuracy, for a total of 91.9% agreement with visual classification. In order to evaluate whether the function is applicable for samples from outside the Philippines, a double blind test was conducted with a large sample of deformed and undeformed crania from a broad geographical and temporal range. For this sample, the function agreed with visual classification in 89.7% of cases; 98.8% of undeformed crania were correctly classified, while deformed crania were identified with 73.7% accuracy. These results demonstrate the utility of the new discriminant function for the classification of artificially deformed crania from diverse contexts.

Possible causes and significance of cranial robusticity among Pleistocene–Early Holocene Australians

“…About the Cohuna cranium in particular he wrote, ''although flattening off at least the upper zone of the frontal, the deforming influence may also have had the effect of increasing vault height near bregma and producing a somewhat unusual angular relationship between the frontal and parietal surfaces'' (Brothwell, 1975, p. 77). Later, Brown (1981), Antó n and Weinstein (1999) and Clark et al (2007) agreed with Brothwell's assessments. Although the evidence has been reconsidered to some extent by Curnoe and Thorne (2006a), the present author now accepts that KS5 may have been artificially modified.…”

A metric study of three types of artificial cranial modification from north‐central Peru

“…Many use broad categories, contrasting 'fronto-occipital deformation' (Cheverud et al, 1992;Clark et al, 2007) or 'antero-posterior deformation' (McNeill & Newton, 1965;Antó n, 1989;Rhode & Arriaza, 2006) with 'circumferential deformation', or 'vertical' versus 'oblique' occipital orientation (Moss, 1958). However, such systems may mask interpopulation variability in cranial form.…”

“…Variables to be included in the analysis were selected from those giving significant differences in the ANOVA results, and sample size was also taken into consideration to maximise the number of specimens included. Clark et al (2007) recently applied discriminant analysis to craniometric data from artificially modified samples in order to develop a general equation to assist in distinguishing artificially modified and unmodified crania. Their focus was therefore on common features of different types of ACM, specifically cranial shape in the sagittal plane, in order to achieve maximum separation of modified and unmodified crania.…”

“…It has been suggested for the Dynasty of Akhenaten in ancient Egypt (Snorrason, 1946), and was common in certain districts of 19th century France (Dingwall, 1931). The earliest certain cases of ACM come from Late Palaeolithic Australia and China (Brothwell, 1975;Brown, 1981;Clark et al, 2007).…”

“…Indeed, the lack of clear distinction between unmodified and artificially modified crania can be problematic for a variety of modification types (e.g. Clark et al, 2007), but is a particular problem with such a mild form of ACM as posterior flattening. This may also have implications for the methodological approach taken here where crania were categorised as modified or unmodified from the outset as there may have been some degree of misclassification.…”