In physics, scientists say that:
Energy cannot be destroy or created, but can change from one form to another.
Spirits is a type of energy...
It cannot be created as well
And cannot be destroyed.
It will only change from one form to another
--> so....we will reincarnate into different, changing our form from human to deities, from deities to animals, from animals to asuras, from asuras to hungry ghosts, from hungry ghosts to the souls in hell....
Do you know what form you are going to change to...?
One thing for sure is that, we can control what form we want to be...
That's some mysterious answer, when science meets religion.... It is not something that is contradict to each other, but it support each other. Religion is something about the truth. science is something to trace the truth!