Original idea by @DonnKing. I've used this before recently, but it's a perennial favorite. ;)
1. What if we were herbivores?
Would our society be more peaceful then?
2. What if our bodies didn't have a natural expiration date?
Like Tolkien's Elves.
3. What if we were only a meter (three feet) tall?
Would we then have succeeded in hunting mammoths and subjugating nature with its lions and tigers?
4. What if we were hermaphrodites?
Like the residents of Ursula K Le Guin's Winter Planet.
5. What if the concept of humor didn't exist for us?
Other animals don't seem to know it.