What would happen if†men could menstruate and women could not? Clearly, menstruationwould become an enviable, boast-worthy, masculine event: Men would brag about how long and how much.Young boys would talk about it as the envied beginning of manhood† Generals, right-wing politicians, and religious fundamentalists would cite †'mens-truation'as proof that only men could serve God and country in combat† If men could menstruate, the power justifications would go on and on. If we let them.

-Steinem, Gloria
  'If Men could Menstruate', collected in Outrageous Acts and Everyday Rebellions (1983).