I believe that it occurs at conception - at the moment where the sperm and the egg meet, the energy that makes the cells 'combine' (so technical I know) and become the first cells of the baby, is the 'soul' or spirit. It follows my belief in one of the law of physics - conservation of energy: energy is neither created nor destroyed. I believe that the energy it takes to create a baby from a sperm and an egg comes from the spirit.

It's interesting reading everyone's thoughts and beliefs.