I suppose if one had no exposure to animals that weren't in some sort of solitary confinement, had parents that were seemingly asexual when not behind closed and locked doors, had no older siblings or precocious friends, wasn't much of a reader beyond the Little Golden Books, never watched TV or movies, never ventured out in public, walked through the halls of Jr. and Sr. Highs with eyes locked on one's own feet, had no instinctual understanding of themselves/their bodies, and had parents who never answered questions honestly...(and in today's world I'd have to add had no access to unsupervised internet use)...then perhaps I might understand how a child could make it to their teens without a clue.
As it turned out my parents weren't super straightlaced, lacked a bedroom door lock, we had a one-room cabin where as many as ~ 20 of all ages would stay the weekend, I had five older brothers, a free-range childhood, I was a voracious reader, had a good level of self-awareness, I shared a bedroom with two brothers until I was 12 or 13 and we had a single bath for the 8 of us, and we had a multitude of pets...including my longest-lived cat who was the town slut and a doberman who was quite attached to a friend's leg. I was also an aunt at 11. No...it wasn't too terribly difficult.
I'm seriously thinking about doing just that. Yikes!
Might curl your toes.
Way after the fact.
My father never talked to me about sex, but gave me an old medical book that supplied correct technical information, and had black-and-white pictures in it of unattractive naked people with horrible diseases and genetic syndromes. That scared me away from sex for some time...