One theory that I have heard of is that our souls spend time on other planets, so that all possible souls are not here at the same time. In those other planets or realities, we may have different forms than what we think of as human, or we might merely be pulsing balls of light. When a big shift happens (like now) many souls congregate who hadn't been here before. Like a college curriculum lots of them have a final earth credit to earn so they come to Earth school.
(And if that's the case, then I wonder how many people have migrated here from planet Stupid.)
BTW, I like your theory, Dan.