I don’t think there’s any mainstream religion out there that doesn’t assume the existence of a soul, nor that there is anyone out there who would need the explanation of what is meant by it. Still, I’d say that the soul is nothing but a fancy name for consciousness. And that definitely doesn’t have to be something breathed into us by some higher spiritual existence. Even less does it have to be something unique to humans, however painful that is to certain people to hear. Remember that only a few hundred years ago (and I daresay deep within even today), “civilized people” still refused to consider others humans just because the color of their skin.