One of the comments reads : Actually, we will probably never figure out, was it man or woman. but I thought this comment of the professor was an interesting eye opener. https://mastodonapp.uk/@MarkHoltom/112070436760917344
You mean apart from them occuring at set intervals? The length of time between the average women's periods is 28 days, but the moon's 28 day cycle is 100% reliable, and always happens regardless of individual stressors. Having a regular solar event that confirms you're accurately keeping track of days is pretty practical.