Have you ever wondered where in the human body our soul is located? Not me. Not until someone asked. Maybe because it doesn’t sound like the right kind of question, like asking how much the color blue weighs. Someone asked “how does God attach the soul to the fetus, and when does He do it?”
Implicit in the question is that the soul is a material thing. And unless you can attach a thing which has no physical properties the question isn’t coherent. I think the soul isn’t a physical thing and therefore isn’t attached or added.
I think our soul makes us God-conscious. It makes us aware of the existence of something bigger than we are: God. If this is true it explains why we don’t see god worship in other species.
I haven’t put a lot of thought into this particular topic, but as best as I can tell, the soul is to the human body what consciousness (or the mind) is to the brain.
Thoughts?
Sifting Reality 
I think the mind and the soul are the same thing. Sometimes soul and spirit are used synonymously in scripture, while at other times (Hebrews 4:12) they are spoken of as distinct. I sort of see the spirit as being WHAT we are – we are spiritual beings.
John,
The question is a little different, but the material-nature of the soul is nothing new. In 1901, Dr. Duncan MacDougall weighed patients in the process of dying from tuberculosis. The whole bed was placed on an industrial scale and different measurements were taken as the process moved along.
According to Dr. MacDougall, the soul left the body at the time of death – measurable by a drop in weight, This meant the soul was a material thing that had a mass.
Clearly, the tests were methodologically flawed. But it’s interesting nonetheless.