I try to give religious beliefs that differ from mine as much slack as possible. After all, faith by nature is based on the unprovable: virgin births, burning bushes, miracles, promises of godhood, giving away 10 percent of your money with the belief that it will be returned to you tenfold...
But one I just can't wrap my open mind around is reincarnation.
It just doesn't make sense. Especially human-only reincarnation, meaning your soul has inhabited one body after another since the beginning of humankind. A quick look at Wikipedia's global population numbers over the past 300 years proves that there just aren't enough old souls to go around. In 1750 there were 791 million people on the planet, and in 1999 there were nearly six billion. What this means is if human-only reincarnation exists, it's insignificant because either souls from 258 years ago are split into more than seven new bodies (is that even enough soul to go around?) or six out of every seven people walking around today are new, never-reincarnated souls. With those odds only three players on the field in any football game are likely to have been recycled from someone who was around circa the Revolutionary War.
It seems more reasonable that reincarnation could encompass all forms of life. The numbers would conceivably work out because no one knows how many bacteria or gnats there are running around. But to believe that souls work their way up or descend through the evolutionary food chain as if on a baseball farm team doesn't quite fly. Say you steal a lot of cars and are punished by coming back as a monkey. How do you live a virtuous life and work your way back into humanhood when you're stuck as an animal that acts solely on instinct? Throw less poop at kids who watch you at the zoo? Save a panda from an alligator attack? Star in a film with Annette Funicello?
Granted, maybe reincarnation works in some way I'm incapable of understanding. Like maybe we get reincarnated among a universal pool of intelligent life that spans the universe. If so, I'd like to put in a request to be reborn as an Orb in the Orbulon galaxy because I hear they serve good onion rings there. But whatever happens I don't want to come back as a gray, almond-eyed Area 51 alien who's into anal probing. Because anally probing kidnapped humans just isn't cool. In fact, that's the sort of behavior that'll get you reincarnated as a monkey.