///Just assuming for a minute that reincarnation is as you say, where do all the 'new spirits' come from to account for population growth?///

If you're suggesting new spirits are being created all the time, where is the energy coming from since it can never be created or destroyed? So if a fixed amount of energy can accomodate all these new spirits, so can a fixed amount of consciousness. By what method, who knows? We don't have enough information to bother worrying about it.