What is the most important invention ever made by man kind?

Answer 1

Wow, talk about your wide open questions! Arguably, the single greatest 'invention' is language. It allows us to discuss all the other inventions. Some people can argue that language is not an invention, but rather an extension of human's natural abilities. You could argue that the scientific method is also important. Without the requisite curiosity that is the hallmark of the scientific method, humans would still be mindlessly picking navel lint from their collective bellybuttons. Of course, with language, we could at least discuss the texture of said lint.