# Why does the human menstrual cycle = lunar month?

**URL:** <https://boards.straightdope.com/t/why-does-the-human-menstrual-cycle-lunar-month/82803>\
**Category:** Factual Questions\
**Created:** [September 20, 2001, 3:41pm UTC](https://boards.straightdope.com/t/why-does-the-human-menstrual-cycle-lunar-month/82803 "2001-09-20T15:41:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Yumanite](https://avatars.discourse-cdn.com/v4/letter/y/b487fb/32.png) [@Yumanite](https://boards.straightdope.com/u/Yumanite)\
**Post date:** [September 20, 2001, 3:41pm UTC](https://boards.straightdope.com/t/why-does-the-human-menstrual-cycle-lunar-month/82803/1 "2001-09-20T15:41:38Z")

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Someone asked me this last night. I hypothesized that it might be the result of a selective process – for instance,  
if I, an aware human being, wish to deliberately conceive, I will have a better chance of doing so if I can gauge when I’m fertile by external cues, such as the phase of the moon. So a regular cycle about a month long will lead to greater reproductive success.

I have to admit that I am skeptical of my own hypothesis, but I have never heard or read anything about this. Does anyone wish to shed some light on the subject?

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [September 20, 2001, 3:53pm UTC](https://boards.straightdope.com/t/why-does-the-human-menstrual-cycle-lunar-month/82803/2 "2001-09-20T15:53:50Z")

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[the Master speaks](http://www.straightdope.com/columns/990924.html)