Typical age for girl to hit puberty? what is the average age that girls begin puberty? how long does it last? what causes some girls to start extremely early and some to start extremely late?

The : The average age of puberty and menstruation (first period is called menarche) has steadily declined over the last 30-40 years. Now, menstruation normally begins between the ages of 11 and 13 years old. Menstruation is the defining moment of puberty for women, but there are events that happen first...Breast bud development, pubic hair development, rapid growth, etc. Genetics plays a large part in when puberty occurs as well as exposure to environmental Estrogens and other hormones.

8.5 -13 years: First sign of puberty is breast development. Normal age range is 8.5-13 years. Once puberty starts, it takes about 2.5-3.Years before having your first period. Early puberty in girls is common and is usually idiopathic and benign. There is a large list of causes of late puberty which would be too hard to talk about in this forum.