The Dolphin Population

I was at a huge aquarium standing at a glass wall with a dolphin on the other side. I was contemplating the beginning of the book Hitchhiker's Guide to the Galaxy and pondering whether dolphins really could be more evolved than humans. A young kid standing next to me began banging on the tank like he was knocking on a locked door and zombies were chasing him. I said something about how I don't think animals like it when you bang on their cages, but one of the dolphins actually swam over by us. I was wrong; you'd think that after people banging on their tanks all the time they'd get annoyed, but...then the dolphin went to the bathroom right next to the kid's head and swam off. No matter how supremely evolved dolphins are, it's good to know they're not unapproachable eggheads and still have a great sense of humor.