Considering how the universe is full of stuff circling around stuff circling around stuff circling around... the zodiac signs have moved over the last couple of millenias.
Not that I believe in astrology, but just because the constellations moved doesn't mean that humans weren't able to track them. They still form a ring around Earth and the precession of the Zodiacs still occurs.
I believe the point is not that the zodiacs don't occur at all, it's that the time you are born is no longer the same time the original zodiac occured.
The fact humans are able to track them is how we know the zodiacs are no longer accurate. According to astrology if you were born on Dec. 1 for example, you're considered a Sagittarius... except you're ACTUALLY a Scorpio, due to the constellations shifting.