A soul is just energy. The animating force, I think they used to call it. If you're alive, you have one. I've met all kinds of different races of aliens on all kinds of planets, even machines, and I'd say every one of them had a soul.

Think of it this way. The universe had the big bang, right? A spark that started everything and without which nothing would exist. For living things, that's your soul. The moment you came into existence and became you, you proved you had one.