Secular changes in the Japanese head form viewed from somatometric data

• Published in: Anthropological Science Vol. 112; no. 1; pp. 41 - 52
• Main Author: KOUCHI, MAKIKO
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo The Anthropological Society of Nippon 01.01.2004; Anthropological Society of Nippon; Japan Science and Technology Agency
• Subjects: Anthropology; brachycephalization; Craniology; environmental factors; growth; Japan
• ISSN: 0918-7960; 1348-8570
• DOI: 10.1537/ase.00071

The purpose of the present study was to assess evidence of secular changes in cephalic measurements and to clarify the causes of brachycephalization. Somatometric data of the head and face were investigated for secular changes by comparing data measured by the same observer for 2 groups of subjects differing in age by 45 to 50 years, and by examining trends of the last 100 years. Relationships between measurement, birth year, age at measurement, and year at measurement were examined using partial correlation coefficients. A positive secular change was observed for head breadth, which had a pattern of change that was very similar to that of height. Head length first decreased and then increased. No trend was observed for bizygomatic breadth when the year of measurement was considered. It appears that thickness of the soft tissue on the face is significantly influenced by nutritional status at the time of measurement. Measurement errors in total head height were apparently too large for analysis of secular changes. The parallelism between head breadth and height suggests that nutritional improvement in prenatal and early postnatal life is a plausible cause of the brachycephalization in the last 100 years. The finding that face measurements do not show clear secular change may indicate that they are more strictly determined by function than is the case for measurements of the neurocranium. As possible causes for the difference in secular change in head form/dimensions between Asian and European populations, differences in timing and dominant direction of the very rapid growth of the brain are discussed. There is inconsistency between the pattern of secular change in the 20th century and that of the 14th to 19th centuries. The possible causes of this are also discussed.