Maybe when we die our so called spirit progresses to a different physical being or body.This would be given that should we progress according to the evolution of the universe.  If you believe in reincarnation, it might be possible that a person is reincarnated as another being or species further along a specific spiritual path I guess I could say. Maybe each species in the universe exists on a different spiritual plain and the life you live now will determine the outcome of your next existence, species ect....  on this earth or elsewhere....