Adolescent Growth Spurt
The human adolescent growth spurt is the rapid and intense increase in the rate of growth in height and weight that occurs during the adolescent stage of the human life cycle. The human adolescent growth spurt is noted in virtually all of the long bones of the body and most other skeletal elements. The major exception is the female pelvis, which follows a smooth and continuous increase in size until adulthood. No other primate species, including the chimpanzee, is known to have such a global post-pubertal increase in skeletal growth velocity. Male chimpanzees usually have a spurt in body mass at puberty, due to rapid muscle growth. In humans, the hormones responsible for sexual maturation also cause the adolescent growth spurt in stature and other skeletal dimensions and promote the adolescent life history stage. The growth spurt, which is a notable feature of the human adolescent growth stage, but not the only defining characteristic, begins on average at 10.0 years for girls and 12.0 for boys, however there is considerable variation between individuals and populations. The intensity and duration of the spurt is, on average, greater for boys than for girls, and this accounts for the average sexual dimorphism of 11-13 cm in height between adult men and women. Up to 10% of clinically normally girls, usually those who sexually mature at a late age, experience a small or absent growth spurt. The adolescent spurt and growth of the skeleton ends at about 18-19 years for girls and 20-22 years for boys, and with this the adulthood, or reproductive stage of life history, begins.