Whence comes the soul?

It seems to me, a crucial point of dissention between atheists and religious folk is the existence or nonexistence of an immortal soul. Let's examine this for a moment.
If we have an immortal soul with the abilities to survive our own physical death living on into eternity in either perpetuated bliss or torture and to house our affects such as empathy, compassion, the sense of justice, etcc, then this very soul must have come from somewhere.
As I see it, there are only two possible sources for this mysterious component of us, inside of god, or outside.
If our souls came from inside, or the mind, of god, then he would certainly have known of us (meaning every single human that has lived or ever will live on thisearth) since his own beginning (of which there are many unsubstantiated claims by christians). If god indeed has known each of us, all along since his own inception or birth, then why would he need or even want to create a corporeal body to put us into? We were already with him in his mind, so why did he bother with creation at all? It couldn't be so he would have companionship. He already had it, albeit through multiple personality disorder :-)
If this is not the case and our immortal soul came from outside of god instead, then as I see it,our soul could only come from two possible places outside of god, namely heaven or earth (hell can't be included because, according to religious doctrine, it has not always existed, only coming into it's existence after satan's fall from grace)
If our soul comes from heaven, which is where god himself lives, then as stated before, we have been with god (in his mind) since time immemmorial, leaving no need for him to create an elaborate universe, complete with galaxies, black holes, planets (such as our home), an ordered periodic table of elements identifying the very elements which we, his mind's picture are made of, or all varieties of animals with whom he apparently has no other use for except their ritual death. I again ask why god continually feels the need to create for us, physical bodies that house the soul that, if left alone, would still be living side-by-side with god in heaven. It seems pointless.
If however, our soul did not come from heaven, then it must have come from earth. This of course leads to the conclusion that our soul is actually our concious mind, as it has evolved, along with every other part of our physical makeup, through the eons of the age of the earth. There was never any need for god to create a body to house our immortal soul, because

1. Our "immortal soul" is most assuredly not immortal. It is a function of our biologically organic brain; located in the left pre-frontal cortex, susceptible to illness, disorder and death just like every other part of our organic bodies. When we die, our brains will die and along with them, our "souls". Any belief to the contrary is simply blinded wishful thinking.
AND
2. God doesn't exist except in the neurological pathways of our imagination. He is imaginary and unnecessary. He didn't create anything, especially not the complexity and wonderfulness of life and humanity. You can't create something if you don't exist.