Periods. They're the bane of women's lives from early puberty through to middle age, but without them, human life would cease to exist. A period, or menstruation, is a sign that a woman is fertile and able to reproduce. Without a period, there is no egg to be fertilized by a man’s sperm. The reasons why women have periods is a complex process involving hormones, the brain and the woman’s reproductive system and they’re a vital part of the human life cycle. Read more ...