3 ms·

Related, girls (women?) are starting their periods about 5 years sooner compared to 100 years ago: https://en.wikipedia.org/wiki/Menarche#Changes_in_time_of_ave

• perardi 6y ago
  Per Wikipedia, and other sources I’ve read, it seems heavily correlated with BMI. Which…makes a naïve sort of evolutionary sense. You need some percentage of body fat for your body to kick into reproduction mode.
• joncrane 6y ago
  This has to do more with better nutrition and comfort than anything else. While it's true that estrogen-like compounds may also have an effect, it takes calories to ovulate and to menstruate.