Pre-religion, no, I don't think so.
Some religious households are frankly insane and raise their young to specifically avoid such discovery and exploration of genitalia. Don't forget there are religions in the world where women's genitals are mutilated to such an extent as to remove the clitoris entirely.
There's also a somewhat common condition [1] of the foreskin where it's relatively small and too tight around the head to be pulled back and cleaned. Imagine a young man having such a condition in such a conservative household where nobody ever discussed his penis beyond the minimal potty-training.
The 4chan story I mentioned in my previous post appeared to be such a case of a tight foreskin, where he had simply never pulled it back because it didn't seem possible. The level of ignorance about his own anatomy was genuinely shocking, and if there weren't such obviously authentic amateur cell-phone photographs accompanying the whole ordeal I would have been certain it was fake.