Evidence gathered from scientists clearly suggests that puberty begins earlier than it used to. Some of this evidence evaluates the falling age of menarche, which is the onset of a girl’s menstruation. Other evaluations consider the first ejaculatory erections of boys, or the general onset of puberty symptoms like breast buds, and the growth of pubic hair.
In evaluating menarche, the average age first menstruation begins is 12.2 years, in most Western countries. In contrast, approximately 100 years ago, the average age of puberty as assessed by first menstruation was 13.9 years old. This is clearly a significant difference.
While consistently a larger percentage of girls begin puberty sooner than boys, evidence suggests that boys may also go through it sooner. About 7% of boys reach sexual maturity by the age of eight. Even 40 years ago, less than 1% of boys reached sexual maturity by that age.
Some reasons have been suggested for early puberty. Better nutrition is considered a leading cause. More body fat and more body mass means the body is physically ready to begin this stage. However, excess body fat due to less exercise often leads to early development as well.
Some suggest that chemicals present in food, like hormones given to animals that are then consumed by humans, may result in earlier development of puberty. As well, some studies have shown that stress actually corresponds with earlier puberty, particularly among girls.
Earlier age of puberty should not be confused with the medical definition of precocious puberty. This is defined as premature onset of sexual development. Girls entering puberty prior to being eight years old, and boys who start prior to the age of nine, are thought to have precocious puberty. This condition is most likely to occur among girls who are obese. However, it may also be genetic. Sometimes premature development, especially in very young children indicates tumors causing hormonal imbalance or production.
Precocious puberty can be extremely challenging, particularly for young girls. Their rapid maturation does create notice among peers and may cause social difficulties. However, early signs, like breast buds, may not always be followed by early onset of menarche.
Particularly in girls, those who seem to go through puberty later, and have later menarche rates often are very active in sports, small in build, or who have mothers with a later menarche rate. It is not uncommon for girls who are competitive athletes to begin their periods after the age of 15 or 16.