When I was in elementary school I still didn't know how do people reproduce - I knew nothing about getting pregnant and producing semen, all I knew was that baby is born in woman's stomach. So no wonder I thought that people had 'invented' sex because had discovered that males have penises and females have slits so as they were perverted they started playing inserting penis into that slit. How good I didn't tell somebody about my 'revelations'!
A childhood belief about reproduction

others believed things like this
- I used to think that to give birth, a woman had a slit cut into her inner thigh, and the baby would come out.Anon
- I thought that all cats were the females, and that the dogs were the males.— opps guess not
- When I first started to develop my breasts I thought it meant I was producing milk— trisha
- I use to believe that the man peed in the woman to get her pregnant. Didn't know about sperm until sex ed. — das
- When I was younger I thought that when a woman was pregnant she would feed her baby through her belly button!— Hennie
- I used to think that spam was semen so I was very confused when people talked about buying it in tins.— EB