Culture and menstruation the ideal of synchronised tidal, lunar, menstrual and seasonal periodicities whose overall harmony (it is believed) confers spiritual power and fertility. To many, such cultural associations appear persuasive in view of the fact that in humans, the menstrual cycle quite closely approximates the moon's 29.5-day synodic cycle, unlike in chimpanzees (~36 days) or bonobos (~40 days). Statistical information from hunter gatherers is lacking, but where large-scale western studies focus on women's peak reproductive years—removing outlier values—the cycle length gravitates around 29.1–29.5 days, while the figure for women in their thirties shortens toward 28 days. In no extant human population has
Menstrual cycle half months postpartum. There is a wide range of response among individual breastfeeding women, however, with some experiencing return of menstruation at two months and others remaining amenorrheic for up to 42 months postpartum. The word "menstruation" is etymologically related to "moon". The terms "menstruation" and "menses" are derived from the Latin "mensis" (month), which in turn relates to the Greek "mene" (moon) and to the roots of the English words "month" and "moon". Even though the average length of the human menstrual cycle is similar to that of the lunar cycle, in modern humans there is no relation between