There are a lot of souls in Heaven or whatever you call the alternate dimension where disembodied minds exist before (and after?) they enter human/other intelligent bodies. Earth was an exciting new world back when I applied to join it, around 15000 BCE. Cold yet rapidly shifting climate, humans all over the planet and spreading rapidly, lots of interesting rituals and symbolism, many big animals to eat, everything someone like me needs. They even had a position called "shaman", which I'm really suited for. So I applied for a shaman role in Ice Age Europe.
But of course there was a huge backlog of applications and we had to wait our turn. Most of us got placed in the giant population bubble of c. 1800-2150, because that's where the most openings were. I applied 17000 years early like I was supposed to but I still had to wait until 1989.
Now my role doesn't exist, and clearly most of the other roles my co-applicants are suited for are gone as well. Nobody seems to know what they're doing anymore, and many people are staring at glowing rectangles and feeling miserable.
This isn't totally a rant - if I'd been placed when I applied and everything had otherwise been the same, my mother probably wouldn't have been able to bear me and we'd both have died. I'd have to go back to Heaven and wait in another 17000-year line for a different planet. And about half the time I would have died young from falling down and breaking my leg and having the compound fracture get infected and turn into gangrene, or because the neighboring tribe decided to raid us and I was in the wrong place at the wrong time, or some similar thing. But the other half of the time, shaman-me would have been far more fulfilled in his life than I could be in this one.