In Humans
Before puberty, the abdominal region of both males and females is covered with very fine vellus hair. In response to rising levels of androgens (mainly testosterone) during and after puberty, the skin of the abdomen begins to produce coarser, longer and more pigmented hair (terminal hair). This process affects primarily men. Initially hair grows in a vertical line from the pubic area up to the navel and from the thorax down to the navel. Slang terms for this line of hair include "happy line", "happy trail", "snail trail", or "treasure trail". Although the development of abdominal hair normally begins during puberty, it may also start later, between the ages of 20 and 30. With some men, the abdominal hair will stay within a clearly defined vertical line, but in others, terminal hair will appear laterally as well as vertically, particularly in the area around the navel. This lateral spreading can continue into middle age. The study noted below found that two in three young men have a (sagittal) "treasure trail" by the time they are seventeen, and nearly half have one by the time they are fifteen.
Some women may develop a small line of hair from the pubic area up to the navel. Excessive abdominal hair on women, following the male pattern, is a type of hirsutism.
Read more about this topic: Abdominal Hair
Famous quotes containing the word humans:
“The worst condition of humans is when they lose knowledge and control of themselves.”
—Michel de Montaigne (1533–1592)
“...there is hope for a tree, if it is cut down, that it will sprout again, and that its shoots will not cease. Though its root grows old in the earth, and its stump dies in the ground, yet at the scent of water it will bud and put forth branches like a young plant. But mortals die, and are laid low; humans expire, and where are they?”
—Bible: Hebrew, Job 14:7-10.