Well I think we can all agree (can we?) that we can look at different parts of nature and see neurological processes becoming more and more simple. Eg:
Single cell creatures - completely basic response to environment, no instinct even - relies on environment being perfect.
Parasites + worms + cocroaches etc - basic survival instincts - poke it and it'll run.
Mice, possums - Survival instincts + can learn from mistakes well.
Dogs + Horses - Problem solving - comes across a fence, looks for ways to get past it.
Humans - Able to wonder about stuff like this!
See what I mean? There doesn't necesarily have to be some kind of "soul" or "spirit" behind us, each step of evolution is just the basic elements of life, just aranged in more complex and BIGGER ways, not necesarily hiding some greater thing than a mushy brain. :P