One in four men begins to go bald by age thirty. By age sixty, it goes up to 2 out of 3 men are bald. Women can get male pattern baldness, too, but it is not as common. This runs in families and usually comes from the mother's side of the family. If you are a man and want to know if you are likely to go bald, look at your mother's father to get your best guess.
Hair has a limited life span.
The normal growing phase of a hair follicle can last up to 5 years before the hair is dislodged by new hair growth. In male pattern baldness, when a hair falls out, a new one does not start to grow. This usually happens above the forehead, giving the familiar receding hairline look. It also happens at the crown of the head. Over time, the bald spots increase in size until the entire top of the head is bald and there is only hair on the sides of the head.