Examining Cranial Morphology of Asian and Hispanic Populations Using Geometric Morphometrics for Ancestry Estimation

Abstract

Poor classification trends of Hispanic individuals have been shown when using the statistical software Fordisc 3.1 (FD3), which is commonly used by practitioners to estimate ancestry for unidentified skeletal cases (Jantz & Ousley 2005; Ousley & Jantz 2012). Similarities in craniometric dimensions were identified between Asian and Hispanic groups when performing discriminant function and canonical variate analysis using FD3 (Dudzik & Jantz 2016; Jantz & Ousley 2005). Hispanic cases were shown to often classify as Asian and showed a particularly close relationship with Japanese individuals, as illustrated by small Mahalanobis distances. This study further explores these misclassification trend findings by comparing craniometric analyses with geometric morphometric approaches to better identify morphological overlap between Asian and Hispanic populations. Geometric morphometric analyses have become increasingly useful for studies of cranial shape, and inter-landmark distances have been shown to more accurately estimate population affinity than standard cranial measurements (Spradley & Jantz 2016). Based on this evidence, a more detailed analysis of the morphological similarities between Asian and Hispanic craniometrics is warranted using geometric morphometric approaches. Data sets used include coordinate data of a subset of the Hispanic sample included in FD3 as well as individuals from Japan, Thailand, Korea, and China. Results show that variation among samples can be better identified to describe which dimensions of the cranium exhibit the most overlap across populations. Specifically, comparisons between the Asian and Hispanic data showed that the position of landmarks mainly representing dimensions of the neurocranium are useful for accurately predicting group membership.