Secular and age-related dynamics of biological characteristics in the rural population of Mongolia: a study of environmental adaptation

This study explores temporal and age-related variation of anthropometric, physiological, and radiographic data collected in 1986-1990 in five rural Mongolian populations (four Khalkha and one Khoton) living in different natural environments and practicing a traditional lifestyle. The sample includes 970 adult men and women aged 18-80. In Khalkha Mongols, the impact of climate and other environmental characteristics on anthropometric traits is negligible. These groups demonstrate temporal stability of anthropometric traits over the last 40 years and, if published data are considered, since the late 1800s. Age changes in hand skeleton are low to moderate. Sexual maturation in females is slow, the average age at menarche is 15.8 years, and no secular trend has been detected. The respective age in Khoton females is even higher-16.8 years. Unlike Khalkha females, Khoton females show a secular trend in body size, whereas the tempo of sexual maturation and skeletal ageing is accelerating. The totality of biological parameters indicates successful environmental adaptation in Khalkha Mongols. The Khoton migrants tend toward the adaptive norm typical of the native population.