Adolescence bridges puberty’s hormones and legal adulthood
From Latin adolescere, “to mature,” adolescence spans puberty toward adult status—often the teens, though biology and law disagree on edges. Girls typically enter puberty around 10–11, boys 11–12, on schedules set mostly by genes plus environment.
Hormones reorganize height, weight, body composition, and heart-lung capacity while secondary sex traits appear. Male facial hair usually starts at the upper-lip corners between 14 and 16 before spreading. Average spermarche and menarche both cluster near age 13, the latter ± a few years and sensitive to nutrition. The trigger is the pituitary gland, which floods the blood with hormones that wake the testes, which chiefly make testosterone, and the ovaries, which mainly make estrogen. A girl needs a certain share of body fat to begin menstruating, so malnutrition, hard physical labour or sports such as ballet and gymnastics can delay it.
Early-maturing boys often gain sports and social attention; early-maturing girls may feel self-conscious and face higher risks of certain pressures. Girls who mature early are more likely to develop eating disorders and may face sexual advances from older boys before they are ready, while late-maturing boys can lose confidence comparing themselves with developed peers.
Growth follows a set order. Hands, feet and head lengthen first, then arms and legs, and finally the torso and shoulders, which explains the gangly look of many teenagers. At peak speed adolescents grow about as fast as toddlers: according to the Harpenden Growth Study, roughly 8.8 to 11.8 centimetres a year for boys and 8 to 10 for girls, with boys' spurt arriving about two years later. Girls usually finish developing around 15 to 17 and boys around 16 to 17, and bones harden as the growth plates at the ends of long bones close.
Definitions vary widely, from as early as 10 to as late as 30, but the World Health Organization counts adolescence as ages 10 to 19. Physical growth and cognitive development can continue past the teens.
Source: Adolescence
