Douglas Adams on dolphins
The quote in Douglas Adams The Hitch-Hiker's Guide to the Galaxy:
"Man had always assumed that he was more intelligent than dolphins because he had achieved so much – the wheel, New York, wars and so on – whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man – for precisely the same reasons."
http://www.workinghumor.com/quotes/hitchhiker.shtml