Morphometric variations and growth of the profile of the face in Chinese boys aged 4-15 years.

Much research has been conducted on the morphological growth and development of Chinese children. However, very few facial measurements have been documented, especially of the sagittal plane of the face. Morphometric variations and growth of the sagittal plane of the face in children were analyzed using geometric morphometric method in this study. The studied sample consisted of 108 boys (4-15 years) from Huzhu County in Qinghai Province of China, which were divided into three groups: 4-6 years old, 7-11 years old and 12-15 years old. It was revealed that the landmark-groups of nose area were relatively long, indicating large variation in the direction of the nasal protuberance, which possibly reflected the vigorous growth of the children's nose. There were larger landmark-groups' variability ranges in children aged 7-11 years, which may be related to the rapid growth in this period. The average morphology of the sagittal plane of the face changed a lot with age, which was showed in the comparison of the averaged graph of three groups: (1) the proportion of the forehead to entire face became smaller; (2) the 7th landmark extruded more noticeably; (3) the nose became protruding; (4) the position of the mouth was relatively getting more upward, and the angle formed between the upper lip and the lower lip increased, and the lower lip moved forward; (5) the chin protuberated. Principal Component Analysis (PCA) revealed significant differences in the main distribution areas between age group 4-6 years and 12-15 years, even though there was a lot of overlap in the three age groups. Allometric analysis showed that the sagittal plane of the face aged 4-6 years and 7-11 years changed in the following way as the size increased: the forehead became vertical and the upper lip turned to be smaller. Additionally, as the size increased in age group 12-15 years, the most prominent landmark of the forehead became more conspicuous, and the bridge of the nose got more upturned. These may reflect the common morphological features and growing development of the facial sagittal plane of Chinese children.

Evolution and migration history of the Chinese population inferred from Chinese Y-chromosome evidence.

Y-chromosomes from 76 Chinese men covering 33 ethnic minorities throughout China as well as the Han majority were collected as genetic material for the study of Chinese nonrecombinant Y-chromosome (NRY) phylogeny. Of the accepted worldwide NRY haplogroups, three (haplogroups D, C, O) were significant in this sample, extending previous assessments of Chinese genetic diversity. Based on geographic, linguistic, and ethnohistorical information, the 33 Chinese ethnic minorities in our survey were divided into the following four subgroups: North, Tibet, West, and South. Inferred from the distribution of the newly found immediate ancestor lineage haplogroup O*, which has M214 but not M175, we argue that the southern origin scenario of this most common Chinese Y haplogroup is not very likely. We tentatively propose a West/North-origin hypothesis, suggesting that haplogroup O originated in West/North China and mainly evolved in China and thence spread further throughout eastern Eurasia. The nested cladistic analysis revealed in detail a multilayered, multidirectional, and continuous history of ethnic admixture that has shaped the contemporary Chinese population. Our results give some new clues to the evolution and migration of the Chinese population and its subsequence moving about in this land, which are in accordance with the historical records.