By: RITWIK BANERJEE
This study compares legacy and modern coordinate systems used in shape analysis, evaluating their impact on morphometric outcomes using a Homo naledi third metacarpal (MC3). Nine fixed landmarks were placed along the palmar curvature of a Homo naledi MC3 (MorphoSource ID: 0000S2122). Thirty specimens were simulated by applying small positional noise to the original configuration. Landmark data were transformed using four coordinate systems: Boas, Bookstein, Procrustes, and tangent space. Mean displacement, RMSE, morphological disparity, and PC1 variance were calculated for each. Bookstein coordinates produced 138% higher disparity and 155% greater PC1 variance than Procrustes. Boas also inflated shape metrics. Tangent space closely approximated Procrustes outcomes. No inferential statistics were applied because the transformations were deterministic. The choice of coordinate system significantly affects shape quantification. Legacy systems may introduce analytical distortions. Procrustes-based methods remain the most reliable for evolutionary morphometric analyses.
