Perhaps with the idea of delaying the inevitable, my highschool-age uncle told us six-year-old boys that girls have teeth in their vagina. Took awhile before I dared to find out the truth.
sex
7,896 beliefs in this area

when I was young I went on vacation with my parents and their friends and I didnt know what a condom was but I had heard the word befor and I asked If we were going to stay in a condom but what I should have said was are we going to stay in a condominum. OOPS
I use to believe that condoms was used for water balloons and air balloons. Boy was i wrong!
pick of the bunch
i used to believe your penis would grow if you masturbated
At around age 11, I was at a friends house when I noticed blood in the toilet after her sister went to the bathroom. I was convinced that she was dying of some dread disease and said so to my friend. Then my friend informed me that it was from her period. Boy did I feel stupid.
Until I was about nine, I thought that breasts were these white, conically shaped, spirally looking things. It wasn't until retrospection years later that I realized that was what the bra my mom wore looked like. (a la 1950's)
When I was around 12-13 years old (old enough to know better) and discussing childbirth with my friend and her older teenage sisters, I revealed that all babies were delivered by cutting open the stomach. I was astounding to learn that babies were usually delivered vaginally. I was totally revolted by the idea, and my friend and the others teased me terribly because of my ignorance and embarrassment.
When I was little, my sister told me that our pet dog had her period and that was why she was bleeding. I went running for my mother screaming that our dog was going to bleed to death from her period.
When i was very little (around 5) I use to think that the pee comes out of a girls clitorus. Intill i asked my mom and she corrected me. Glad i still dont believe that!
My older sister and I found my dad's secret stash of "girlie" magazines one day. One picture portrayed a man with his penis in the woman's mouth, while another portrayed a woman with her mouth on another woman's wet-looking lower extremities.
It was a long time before I realized that they weren't allowing other people to pee in their mouths. (Boy was I disgusted at first.)
As a little boy, I knew that girls and boys had different parts between their legs, but I thought that a girl's parts were the same as a boy's parts, just pushed inside (inverted). Made sense to me.
How did they get that way? Well, at first, boys' and girls' parts were the same, then a dinosaur kicked a girl in the crotch....
I believed that married people had sex once (obviously) and the number of, er, thrusts, determined the number of children. The woman then had a certain number of conceived eggs inside her just waiting to be born.
Also, the first time I heard the word "rape", I misheard it as "rake". I understood it was something very unpleasant, but being attacked with a rake just seemed a bit obscure.
Guess I was dyslexic and didn't know it,but as an elementary student I thought that adults had sex by standing back to back. So any time some kid wanted to measure his or her height to mine, by standing back to back, I'd get terribly embarassed.
I used to believe that you had to be married to have babies, and that what got the woman pregnant was the kiss which takes place at the end of the wedding ceremony.
Shortly before junior high, I had gathered that a "blow job" involved penis-sucking, but I also believed that it was actually a JOB, and that people did this for a living (turns out I was right, but not in the way I thought!). I even went so far as to tell other students that one of our teahcers "had a blow job at night"...man did I get some weird looks...
pick of the bunch
i used to believe that sex involved peeing into girls.
My parents had two friends who were unable to have children. They were both very fat, so I thought that they couldn't reproduce because their large bellies prevented them from getting close enough to each other to have intercourse. Of course it turned out to be a fertility problem...
My Mother was pretty buxom when I was a child, and as was the fashion in the 50's, she wore low cut summer dresses that displayed a generous display of cleavage.
I asked often "where did I come from", all the while being pretty sure that babies originate in their mummies tummies, since an Aunt was pregnant.
How did they get out, was the question?
The little engineer in me for lack of better data, surmised that they must emerge kicking and screaming one day, from that bottomless cleavage.
pick of the bunch
I used to believe that very few people actually had sex and the rest were just lying to impress each other.
pick of the bunch
I first recall hearing the word "virgin" in Mel Brook's "History of the World Part I." I figured that was a term for someone who was a resident of Virginia.