Perhaps (and this is only a suggestion, not an argument) the "breath of life" (Greek 'pneuma') is our spiritual life, our 'soul' if you will--our stake in eternal life. It seems to me that, throughout creation, physical life is fleeting and transient, the stuff of our physical beings endlessly recycled, but that God has also endowed us with an eternal spiritual 'life', and it is the creation of that life that is the subject of Genesis.
That's just a personal notion, of no consequence to anyone else. I merely wish here to point out that other possibilities (which you are free to reject) exist for understanding the scripture you quoted.
I've heard that before but I think that the fact the the reference specifically mentions the material used and then makes the refence to life being given to it, lends it more to a seperate creation act and giving life to something non living. It's the most obvious reading IMO, so I don't tend to look too much deeper when the plain meaning makes sense.