During the formation of the solar system, the gaseous giant planets that make up the outer solar system were pulled much closer to the Sun than they are now, causing absolute chaos in the asteroid belt.
As the gas giants did their dance through the solar system, the planets, from Mercury to Neptune may have been pulled into the asteroid belt. Jupiter most likely caused the most chaos in the asteroid belt by sweeping up all but one tenth of a percent behind.
All of this disruption wasn't a bad thing however. It has long been believed that Earth's water came from asteroid ice. Very likely it was the massive stirring that Jupiter caused brought the material to Earth that was the starting point for complex life.
View the Daily Galaxy blog for the original HERE