I think you're looking at this all wrong. Obviously my view is monistic, but it's supported by theoretical physics as well as the upanishads. Remember that the reality you think is around you is actually all created inside your mind. There's no such thing as "red". There is some substance that reflects those particular light waves that our visual sense identifies as red. These are the forms existing in a substratum of awareness which our bodies navigate and filter and display as reality to that awareness. There is no specific individual us. There is a gross body, a subtle body, and a causal body all navigating that substratum. Remnants of that causal body suffer rebirth - so we try to get rid of attachments and get those remnants to zero to reach sachcidananda. the self. our ultimate form.
Keep in mind that consciousness is past the 3rd dimension so it is not bound by time. That would mean you're not talking about a linear time progression. So the issue of increased population means squat. We are ALL the same substratum of consciousness. we are just stuck circumnavigating the path of our existing karma until we can zero out and break free.