The New Approach Used to Improve Differentiating Potential of the Geometric Morphometrics Method (The case study of urban craniological series of the early Modern Period)

The aim of this study is to test a new approach to the geometric morphometrics method by adding coordinates of size and form to study morphological variations in paleoanthropological groups. The study compared the results of this approach and those of the analysis conducted using geometric morphometrics based only on the shape coordinates and a craniological study. This analysis examined craniological series from Gorokhovets, Nizhny Novgorod and Yaroslavl of the 16th–18th centuries. A total of 57 male skulls were analyzed. The analysis included ten craniometric sizes of the facial skeleton and 3D coordinates of 21 craniological landmarks. A principal component analysis was carried out to study variations. The coordinate data were analyzed twice, at first, to estimate only the shape using Procrustes coordinates and then to estimate the size and form of the objects using Boas coordinates. Statistical analysis was performed using the STATISTICA 12 software package and the RStudio integrated development environment. The analysis of the shape coordinates did not reveal variations in the series. When this approach was employed taking into account size and form, the groups that were shown as different based on the craniometric analysis were also differentiated. Hence, the second variant of the analysis produced results comparable with the craniological results; however, the craniological analysis has a higher reliability of variations in the groups in the space of the principal components. The geometric morphometrics method using the size to analyze variations in the facial skull showed that the use of size and form coordinates to enhance resolution capability to differentiate paleoanthropological groups is promising.