What happens to all those sentient animals we have killed and continue to kill off? The great mystery, in an effort to maintain balance, rather than creating humans a la The Island of Doctor Moreau, "souls" migrate from the former to the latter.

Not sure what the science fiction part of this is.

I'd like to point out a few things about death.

1) Every sentient being "we" have ever killed was going to die eventually anyway. Why would you think something different happens depending on how they die?

2) As bloody as our hands might be, we don't hold a candle to nature. Look at your magnificent evolved body, and realize how many 100s of millions of sentient near-relatives of your had to die to get you here. Look at how strong your arms are and think of how many nearly-ancestors of your were slightly less strong, and lost the race to survive as a result. Look at how smart you are and think of your proto-ancestors who didn't quite make the grade when it came to evading death before reproducing? Every thing which is great about you was won at the price of killing off without leaving progeny your near-ancestors who didn't quite have it as good as you do.

Now THATS some science fiction story!

R:)