This may be because people have better food to eat today. For example, in Norway, girls born in 1840 had their first period (see below) at an average age of 17 years in France the average age was 15.3 years and in England it was 16.5 years. Today, people start puberty younger than in the 1840s. Boys and girls who have a good diet вЂ“ who eat healthy food вЂ“ tend to start puberty earlier. Some studies have found that mothers and daughters tend to start puberty at about the same age. Half of a person's genes come from the mother. Genetics is the study of how parents pass on to their children some of the way they are through their genes.

Here are some of the things that make puberty happen at different ages in people: This is because their environment (things around them) may differ quite a bit. This is the general picture, but people round the world may start puberty at different ages. This can be due to improved nutrition resulting in rapid body growth, increased weight and fat deposition, or eating meat from animals which have been dosed up with oestrogen. In rich countries in the 21st century, the average age at which children, especially girls, reach puberty is lower compared to the 19th century, when it was 15 for girls and 16 for boys. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average between ages 12вЂ“13 for males, it is the first ejaculation, which occurs on average at age 13. Girls usually complete puberty by ages 15вЂ“17, while boys usually complete puberty by ages 16вЂ“17.

On average, girls begin puberty at ages 10вЂ“11 boys at ages 11вЂ“12.

When the amount of estradiol and testosterone in the body increases, various parts of the body change.

Steroid hormones are also made by the body's two adrenal glands, which sit on top of the two kidneys. Estradiol and testosterone are types of hormones called steroid hormones. Both ovaries and testicles produce estradiol and testosterone, but ovaries produce more estradiol and testicles produce more testosterone. A girl's gonads are her ovaries, and a boy's gonads are his testicles (also called testes).

LH and FSH make the gonads grow larger and start producing their own hormones, estradiol and testosterone.

The bloodstream carries these hormones around the body. LH and FSH are types of hormones called gonadotropins.

GnRH causes cells in the pituitary gland to make two hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH).

A gland at the bottom of the brain called the hypothalamus sends gonadotropin-releasing hormone (GnRH) into a nearby gland called the pituitary gland.

Glands are organs (special parts) of the body that make hormones. Hormones are chemicals that tell parts of the body to do things. Puberty is started and carried on by different hormones. The gland makes hormones that cause males' and females' bodies to start puberty. The location of the pituitary gland is shown in orange. Therefore, people in many countries around the world have different ways of marking this event. People often notice boys' voices getting deeper, and girls growing breasts and starting to menstruate (have periods).Д«ecause puberty is the time in a child's life when he or she becomes able to make children, this is seen as very important. These changes are called secondary sex characteristics. Changes that happen to boys and girls during puberty include the sex organs growing bigger, hair appearing on the body, and growing taller and stronger. However, people all over the world start puberty at different ages. Today, on average, girls start puberty at age 10 or 11, and boys at age 11 or 12. Puberty is started by hormones, which are chemicals that tell parts of the body to do things. If he has sexual intercourse (sex) with a girl, he can make her pregnant. At puberty, a boy's body begins making sperm, and he starts to be able to ejaculate, which is semen coming out from his penis when he is sexually excited. A girl who has gone through puberty can become pregnant and have a baby. After puberty, people are able to make children. Puberty is what happens in children's bodies that changes them into adults. When this happens, their bodies change in many ways. Puberty is what happens to the bodies of girls and boys that changes them into women and men.

Puberty voice change