Ancestry estimation using image analysis of orbital shapes from Thai and Japanese skulls

Abstract

The orbital shape is one of the most ambiguous features for morphological study in ancestry estimation. Recent research has used digital image analysis to obtain more objective and better results. The aim of this study was to create a method and formula to determine ancestry using image analysis of orbital shapes from skulls of Thai and Japanese individuals. This pilot study applied two-dimensional digital image processing techniques to analyze 440 skulls comprising 220 modern Thai and 220 modern Japanese samples of known identities. The image analysis involved four steps: pre-processing, segmentation, feature extraction, and classification. Five shape measurements of both the left and right orbital rims were selected and a formula was derived using multivariate discriminant analysis. Another set of 68 Thai and Japanese skulls was used as a blind test set for accuracy. The formula had a predicted and cross-validated accuracy of 80.7% and a tested accuracy of 86.8%. This methodology potentially increases the utility of orbital shapes for ancestry estimation, especially between these two subgroups of Asians.