Death. The soul leaves the body. The body is a shell, nothing more than a vessel for the soul, the fifth, transient element. For example, we call your body "yours." Like a possession. Not yourself. Do you see what I mean? "Self" is personality and thought and memories (not memory). And what is personality and thought and memory? Chemicals in your brain. But not even that. The way those chemicals come together, with the physical tissue of your brain and its orientation in space and time. But these things, personality and thought and memory, self, are not physical, nor would we ever presume to describe them as such. Really, how would we describe them? Abstractions. Not matter, but abstractions. It's a small step from abstractions to energy. After all, how would you describe energy? Try; it's really damn hard. Okay, you can say "I don't know" now. Self is so amorphous, indescribable, intangible, abstract… you get the picture.
Death. I keep wandering away from it (intentionally, perhaps..?). Body is a possession, a vessel, a shell. Even when you're alive. But it's a possession like a home. A house or an apartment. It's very personal, very you. Still, when the soul leaves, it's just a fallen log, a discarded muffin in a muddy parking lot (don't ask), a footprint in wet sand. It's the physical manifestation of memory, a dead body is. I want to be cremated. I want my body to go to the fire. Well, actually it's between cremation or just being left out for the animals and the plants and the elements. Air (the great oxidizer) and water (the great eroder) and earth (the great consumer) and fire (the great equalizer) and life. Other life: dogs and raccoons and birds and worms and beetles and trees and fungi and soil bacteria. Either way I am returned; even if I was embalmed and locked in a metal box and buried (*shudder shudder*) I would eventually return to the universe as organic molecules and even atoms. It would just take longer. Much longer.
One thing about my faith is that it's not particularly comforting. But that's the thing: that's because it's realistic. The world is not "made" for us. We are not "supposed" to be able to survive, thrive in it.
The "meaning" of life is that it works. There is no great reason.
The soul is recyclable, but not always recycled. Yes, reincarnation is in here somewhere, but I've got my own bent on it.
But I do know what happens when you die by a hand or a force other than your own. Sort of. Obviously I don't know, really. I mean, no one does. If only we could remember… Think of the first law of thermodynamics; conservation of energy and matter. Add up all the energy and mass on both sides of the chemical equation and they'll match. Mostly. I'm not going there, at least in this paragraph. Besides, I forget what the principle or whatever is called. Well, what is a soul but… something. I mean, there aren't specifics, but souls are like the gods; they have to be made of something. And there's only two things in the universe (don't you even think about it): matter and energy. Personally I'm leaning toward energy, and it makes sense/sounds good: heat energy, light energy, life energy. You know? But the point of this whole idea is that souls can neither be created nor destroyed (perhaps they can be converted, but not going there right now). Anyway, this means they have to be re-used, and I think they come out the other side looking pretty much the way they did. It's, like, hard to change energy, man…
Whoa, I just started making sense! Like, trippy, right? Betcha didn't see that one coming, huh?
So, souls survive the journey from one body (the deceased) to another (the newly born) pretty much unchanged. I have no thoughts on the actual method of the journey at this moment; I will just say that Death is neutral among divines (I'm not even sure he qualifies as a divine) and men, and there are Angels [of Death] and Reapers involved. What; you thought I didn't have a theory? Silly, silly; you don't know me yet, do ye? Actually, have you been, like, paying attention?
BTW: I've been writing this to myself. Because I talk to myself. I know, circular, but I get hold of an idea and I'm like a terrier with a bone. Never let it go. Just sayin'.
So, I don't really know the mechanism, and the importance of that statement is that I don't know why we don't know who/what we were. I think that now would be the time to point out that souls are present in all living things, so species, even kingdom, is sort of a nonissue.