Marcel Duchamp is usually credited as inventing the readymade,

but the essential idea of taking something preexisting and elevating it into art existed before he created his first one (a bicycle wheel atop a kitchen stool) in 1913. In fact people have been using found objects to make things since the beginning of time, though the use of found objects as an artistic gesture really began in the 1900’s. Human’s have always used what’s around them to help explore or explain their ideas 3 dimensionally.