In fact, the “female reproductive system” does not get pregnant almost immediately at puberty and then spit out a baby every 18 months. Unless of course, the female who owns the reproductive system in question is for some odd reason having coitus exactly from that moment on with virtually no let up. Part of the “naturalness” of the reproductive system is that it depends on coitus, which, barring the commission of a criminal act, is generally voluntary.
So we have a choice here. Tell people not to screw around and they won’t get pregnant—just like we tell them to eat less, not smoke, etc. Or tell them g’head, KEEP screwing around so then we can pump you full of synthetic estrogen and screw up your menstrual cycle.
I am not down on the medical profession for what it does well, and to be sure, it has saved a lot of lives and done lots of goods for mothers and babies. What I am saying is that its uncritical acceptance of the Pill is inherently contradictory and flies in the face of “first do no harm.”
Voluntary coitus from the onset of puberty through menopause is also natural.
There are a lot of good reasons to mess with the menstrual cycle, some of which are secondary to the typical modern lifestyle which typically features little physical activity and too much food. And the little physical activity part just isn’t going to change — the information age is here to stay, and most people need to spend large chunks of their time studying (from childhood through at least early adulthood) and processing information in connection with employment and personal affairs.
But it’s also not natural for women to have a period every month, because it’s natural for them to spend the vast majority of the time between puberty and menopause either pregnant or nursing. I’ve done a fair amount of genealogy research and can say with certainty that I’d had more periods before my 18th birthday than many of my female ancestors had in their entire lives (due to a combination of the much earlier onset of menstruation in modern times, and my ancestors’ non-stop childbearing beginning at marriage in their mid to late teens, which was also the typical age for onset of menstruation in those times). And plenty of research has shown that the hormone levels associated with natural menstruation are what correlate to higher incidence of breast cancer — more periods in one’s lifetime correlates very strongly with more breast cancer.
“Natural” is just not as compatible with civilization and long, healthy lives as many people would like to think.