According to this article from the BBC's Science Focus

Charles Darwin thought that the 28-day human menstrual cycle was evidence that our ancestors lived on the seashore and needed to synchronise with the tides.

Did Darwin ever say such a thing?

The closest I have been able to find from a cursory search is this letter from T.H. Huxley in the Darwin Correspondence Project, where Huxley writes

Fancy lunacy & menstruation coming out of the primary fact that one’s nth. ancestor lived between tide-marks! I declare it’s the grandest suggestion I have heard of for an age

Is there any evidence that Darwin suggested this?


1 Answer 1


Yes. The menstrual cycle is surely one of the "some of our functions" that Darwin speaks of in this passage from Chapter VI of The Descent of Man, and Selection in Relation to Sex:

The progenitors of man must have been aquatic in their habits. [...] In the lunar or weekly recurrent periods of some of our functions we apparently still retain traces of our primordial birthplace, a shore washed by the tides.

  • $\begingroup$ Thanks! And do you have any idea which weekly recurring functions he may have had in mind? $\endgroup$ Commented Nov 4, 2019 at 7:58
  • $\begingroup$ @victorblasjo This link to a searchable copy of The Descent of Man (gutenberg.org/cache/epub/2300/pg2300.txt) will help. Search term "tide" will give you the two relevant passages, in Ch. VI and VII. Darwin never refers to menstruation or menstrual cycles directly, only refers to gestation. However Huxley is justified in his reading of it. btw, the phrase at the end of the second "tide" paragraph, "Man, the wonder and glory of the Universe" is ironic, meant to contrast the prevailing view of humans to the descent from lowly organisms he has just laid out. $\endgroup$ Commented Dec 14, 2019 at 21:52
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    $\begingroup$ Darwin's only example of weekly periods, the duration of fevers, refers to higher mammals, thus only indirectly to Man. Use the link in my other comment and search "regular weekly periods." $\endgroup$ Commented Dec 14, 2019 at 21:56

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