City life and brick and mortar dwellings have made us unaware of a very basic aspect of the moon cycle : a full moon means lights. Which may have had very practical effects in the way of life of your basic hunter-gatherer tribesman, especially pre-fire.

The fact that women's cycles are very variable means the adaptation could have been a weak one ; and that synchronisation within the tribe may have helped to adjust the cycles to the moon's cycles. And maybe the synchronicity happened only because once a yearly cycle was too long for reproductive success, another rythm was needed - and the one given by the moon was fairly convenient for biological purposes.

Un roi sans divertissement est un homme plein de misères