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
Immune cycle Immune cycle The immune cycle is a natural homeostatic oscillation of the immune system when chronic inflammation is occurring. Similar to the menstrual cycle, the exact wavelength and waveform of each particular individual patient is different. That is, different people have different immune cycles although each cycle is typically repeated every seven days. C-reactive protein levels in the blood need to be measured every few days in order to have enough time points to show a repeating fluctuation (a wave-like cycle). This is caused by the synchronous division of T cells over time, with T-effector cells boosting immune activity followed