Does phenotypic plasticity confound attempts to identify hominin fossil species? An assessment using extant Old World monkey craniodental data

It has been hypothesised recently that masticatory strain-induced phenotypic plasticity complicates efforts to delineate species in the hominin fossil record. Here, we report a study that evaluated this hypothesis by subjecting craniodental data from 8 Old World monkey species to ANOVA and discriminant analysis. The study does not support the hypothesis. Characters associated with high masticatory strains were found to exhibit significantly higher levels of variability than low-to-moderately strained characters and dental characters, but the three sets of characters did not differ markedly in taxonomic utility. Moreover, the best discrimination was achieved when all variables were employed. These results suggest that phenotypic plasticity likely plays only a minor confounding role in hominin taxonomy, and that, rather than attempting to exclude phenotypically plastic characters, researchers should simply maximise the number of characters examined.