Could metric measurements of mandibles be utilised to differentiate Indian from Malay ancestry

Abstract

Statement of problem: Differentiating ancestry is complicated since there is no pure race, and no clear-cut boundaries defining distinct races. The mandible has been understudied in ancestry differentiation compared to the femur and the pelvis. Aims: To determine the reliability of mandibular metric measurements as indicators for distinguishing between Indian and Malay ancestry, enabling their potential use in estimating other ancestries. Materials and methods: 72 dry mandibles were examined, comprising 36 from India (male: female ratio 31:5) and 36 from Malay regions (male: female ratio 18:18). These mandibles were collected from the late 19th century to the mid-20th century. Digital callipers and a goniometer were used to measure 27 parameters in millimetres. Male and female mandibles were analysed separately due to their role as confounding variables. Eight statistical analyses (7 on males and 7 on females) were conducted using SPSS and SIMCA software. The analyses included the Interclass correlation coefficient (ICC), t-test, orthogonal partial least square discriminant analysis (OPLS-DA) encompassing score scatter plot, variable loading plot, and variable importance of projection, as well as Linear discriminant analysis (LDA) involving Canonical discriminant function coefficients, Wilks' Lambda function, and Accuracy rates of predictions. Results: The study identified robust ancestry indicators, notably the right mandibular angle (MDA Rt) for Indian and Malay male mandibles (p=0.042, pq score=0.17), along with other measurements: left maximum ramus breadth (MRB Lt), bi-condylar breadth (BCB), and right length of mandibular ramus flexure (RFL Rt). While not showing statistical differences in t-test, these measurements exhibited significance in the OPLS-DA loading plot. MRB Lt indicated strong Indian male ancestry (pq=-0.20), BCB showed strong Malay female ancestry (pq=-0.24), and RFL Rt exhibited strong Indian female ancestry (p=0.16). Conclusion: This study highlights key mandibular measurements that effectively differentiate Indian and Malay ancestral origins, advancing anthropological investigations.