Comparative study on the morphological and physiological growth change in the higher non-human primates within a peri-adolescent period.

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We examined a hypothesis that the fatness is a key for initiating the adolescent growth in the higher primates including human, which is measured by, for example percent fat accumulated. As for the first step, we analyzed the cross-sectional somatic growth data of the Japanese macaques (Macaca fuscata) and chimpanzees (Pan troglodytes). Growth curves, distance and velocity curves of skeletal development in the chimpanzees in terms of TW2 maturation scores, showed that the curves look much like those of humans but with the short "juvenile phase" of delayd development period, and with the longer period from the age at peak velocity to that at the full maturation.Physical change with growth was examined for Japanese macaques, from the view point of physique index which we have devised, and skinfold thickness which indicates the relative amount of subcutaneous fat accumulation. The physique index wihch is calculated from body weight and anterior trunk length is ca.100 at birth in both sexe … More s and approximately 110 in adult females and 120 in adult males. The index decreases with age from infantile period by the beginning of adolescent period, to 90 in males and 95 in females. It turns to rapidly increase in the two sexes from three and four years of age in females and males respectively to four and five years of age respectively. Thus, the phenomenon that the physique becomes fatty in the adolescent period which has been found for humans is also found in Japanese monkeys. Time order in the physique change and the beginning of puberty should be studied longitudinally because the difference in the ages of the two phenomena might be little (probably three or six months). Cross-sectional analyzes could not show clearly whether the subcutaneous fat is accumulated in the period of adolescence.Longitudinal growth study was made on Japanese monkeys with the collection of data by short interval. The study showed that the seasonal growth acceleration/deceleration and the adolescent spurt-like accelerated growth are overlapped with each other, but the latter comes earlier than the puberty (reproductive maturation) which occurred at 3.5 and 4.5 years of age in females and in males respectively. Both of physique index and skinfold thickness increase preceding puberty from summer to the beginning of winter.Next step of the peri-adolescent growth study is to analyze quantitatively the body composition, not only relatively but also absolutely including the measurement of whole body fat. Less