A new paper suggests the likelihood that the early solar system had five gas giants, rather than four, and orbital interplay that ended up ejecting it moved Jupiter closer to the sun, moved Neptune and Uranus further away, and allowed for the sweeping of the inner system so that life could develop.
Jay: Well, something wierd happened out there, to knock Uranus on its side. Velikovsky woulda loved this. He also woulda bent the timescale so as to make this stuff happen in historical times, but he was kinda kinky that way.