Hi Snaketracer,
I think that Tigersoap is on the right track. To my understanding, when dealing with the question of reincarnation, we're dealing with essence, not personality - and since essence is neither male nor female, Leo nor Aries, it's really immaterial to connect the two. With that said, I would think that for each incarnation, things are arranged in such a way to allow the essence to learn or do what it determines most needs to be learned or done in that incarnation. To facilitate this, star signs may come into play, or may be chosen in some way - I can't really know at this point in time.
I think, from our perspective, there are a lot of things we attempt to understand from a 3D linear perspective that aren't really understandable from that perspective - which is part of what makes learning fun. fwiw.