Menstrual cycle The first period usually begins between twelve and fifteen years of age, a point in time known as menarche. They may occasionally start as early as eight, and this onset may still be normal. The average age of the first period is generally later in the developing world and earlier in developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women and 21 to 35 days in adults (an average of 28 days). Menstruation stops occurring after menopause which usually occurs
The Great Pheromone Myth mice and rats is a vestigial organ in humans. Menstrual synchrony has long been viewed as a physiological phenomenon in humans that could only be explained by the exchange of pheromones among women. He argues, however, that methodological critiques of menstrual cycle research and recent research indicate the menstrual synchrony does not occur among women. Finally, he reviews the literature on human pheromones and argues that there are serious methodological issues in all studies reporting human pheromones and that no human pheromone has ever been definitively identified. His conclusion is that human pheromones are a myth that is driven in