How could you even tell if you've personally invented something? You don't know what caused a thought to pop into your head. Heck I often forget things I've said, so I clearly forget things I've heard. I could be fully convinced an idea was my own and still be dead wrong.

Luckily you can build on the ideas of others without being a cargo cultist. Simply verify the sturdiness of the foundation before you go adding an extra wing to the house.