What made Duchamp's Fountain such a turning point?

In 1917 Marcel Duchamp submitted an ordinary mass-produced urinal as a work of art, turned it on its side, signed it “R. Mutt” and called it Fountain. With that the so-called ready-made was born — an ordinary object raised to art by the artist's decision alone — and the door to conceptual art was opened. Duchamp moved art “from the retina to the mind”, and without that gesture today's banana taped to a wall would make no sense. In 2004 Fountain was voted the most influential work of modern art.