Puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average onset of puberty is at 10 or 11 for girls and age 12 or 13 for boys.[12][13] Every person's individual timetable for puberty is influenced primarily by heredity, although environmental factors, such as diet and exercise, also exert some influence.[12][14][15] These factors can also contribute to precocious puberty and delayed puberty.[10][15]
The major landmark of puberty for males is the first ejaculation, which occurs, on average, at age 13.[21] For females, it is menarche, the onset of menstruation, which occurs, on average, between ages 12 and 13.[14] The age of menarche is influenced by heredity, but a girl's diet and lifestyle contribute as well.[14] Regardless of genes, a girl must have certain proportion of body fat to attain menarche.[14] Consequently, girls who have a high-fat diet and who are not physically active begin menstruating earlier, on average, than girls whose diet contains less fat and whose activities involve fat reducing exercise (e.g. ballet and gymnastics).[14][15] Girls who experience malnutrition or are in societies in which children are expected to perform physical labor also begin menstruating at later ages.[14]
Girls have usually reached full physical development by ages 15–17,[2][29][13] while boys usually complete puberty by ages 16–18.[29][13][30] Any increase in height beyond the post-pubertal age is uncommon. Girls attain reproductive maturity about 4 years after the first physical changes of puberty appear.[2] In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.[23][30] Teenage and early adult males may continue to gain natural muscle growth even after puberty.[23]
The age of consent to sexual activity varies widely between jurisdictions, ranging from 13 to 21 years, the average age is 16.[48] Sexual intercourse with a person below the local age of consent is usually treated as the crime of statutory rape. Some jurisdictions allow an exemption where both partners are close in age; for example, a 16-year-old and an 18-year-old. The age at which people are allowed to marry also varies, from 17 in Yemen to 22 for males and 20 for females in China. In Western countries, people are typically allowed to marry at 18, although they are sometimes allowed to marry at a younger age with parental or court consent. In developing countries, the legal marriageable age does not always correspond with the age at which people actually marry; for example, the legal age for marriage in Ethiopia is 18 for both males and females, but in rural areas most girls are married by age 16.
