As far as I know, both the animal and star zodiacs symbolize the 4 elements - fire, water, air, earth. long ago people also tried to find the 5th element - aether. But they couldn't as aether couldn't bring material meaning, and in Japanese elements in was described as something "higher than air" or Heaven.
But as many people suppose, the 5th element (if it were found) would be just something like the ultimate element and there would still be 12 zodiacs in every system.
As for me, I would believe in horoscopes, if someone made me a personal one.
And as i've already mentioned, my sign doesn't suit me at all....