I have no idea why he thinks that the 12 showed up because that is how many periods a woman has rather than how many full moons there are on average. Not that

I have no idea why he thinks that the 12 showed up because that is how many periods a woman has rather than how many full moons there are on average. Not that these are unconnected. As https://qz.com/1706398/the-average-menstrual-cycle-is-not-28-days/ https://qz.com/1706398/the-average-menstrual-cycle-is-not-28... points out, the average woman's menstrual cycle is 29.3 days. The length of a lunar cycle is 29.5 days. That they are so close is unlikely to be coincidence. In fact a close-knit group of women in primitive conditions will synchronize their cycles to each other and then the group synchronizes to the Moon. An evolutionary explanation can be found in the fact that predators can smell the blood from menstruation. Therefore there is a real advantage to having women do this all together, when the moon's light makes defending them easier. It would be more convenient still if women didn't menstruate. However periods seem to have evolved when primates lived in trees. There was no barrier to this since smell is less important for arboreal animals than ground dwelling ones. And once evolved, it is hard for it to unevolve. A side note of evolutionary speculation. Our arboreal ancestry seems to have been when primates lost most of their sense of smell. However in temperate zones, smell is very important for finding food under snow. Is it a coincidence that there are only two species of primates that live in the temperate zone? (Japanese snow macaques are on an island with less competition, and homo sapiens is clearly a special case in a lot of ways.)