The Study of Cranial Shape Variation in a Population from Joseon Dynasty using Geometric Morphometrics

Jung, Hyunwoo; Woo, Eunjin; Pak, Sunyoung

Abstract

Traditional morphometrics uses ratios between measured values such as the cranial index and the upper facial index. However, with these ratios alone, it is impossible to represent the shape of the entire cranium in a three-dimensional space because ratio does not express coordinate data. This methodological limitation of traditional morphometrics makes it difficult to evaluate relations between cranial parts. However, it is important to assess relations between cranial parts because cranial parts change their shapes in an integrated way. Therefore, this study adopted geometric morphometrics to overcome the limitations of traditional morphometrics and provide a more enhanced visual analysis of the cranial shape. Using geometric morphometrics, this study focused on variations of cranial shapes in a population from Joseon Dynasty to obtain their specific characteristics. This study investigated variations of cranial shapes in 57 individuals from Seoul Gyeonggi province who lived in the 15th to the early 20th centuries. The coordinates of the crania were collected by MicroScribe G2X (Immersion Corporation, USA) and statistically analyzed using principal component analysis. The results showed that the variations in cranial shapes of females were reflected mostly in width, length of cranium, position of bregma, shape of posterior part of cranium, and length of facial bone. The cranial shapes of the males varied mostly in length, width, height of cranium, size of mastoid process, and length of facial bones. The cranial length became shorter when the cranial width became broader in both sexes. However, cranial height and facial length showed different variations between the two sexes. In addition, the variation in females only showed evidence of static allometry. The results of this research provide basic information about cranial shapes in a population from Joseon Dynasty and will be useful in future studies such as analysis on between-group differences. By identifying within-group variations first, researchers focusing on between-group differences will likely avoid erroneous conclusions.