It's hard - impossible? - to improve on Mark Twain:
"In the course of my reading I had come across a case where, many years ago, some hunters on our Great Plains organized a buffalo hunt for the entertainment of an English earl. They had charming sport. They killed seventy-two of those great animals; and ate part of one of them and left the seventy-one to rot. In order to determine the difference between an anaconda and an earl (if any) I caused seven young calves to be turned into the anaconda's cage. The grateful reptile immediately crushed one of them and swallowed it, then lay back satisfied. It showed no further interest in the calves, and no disposition to harm them. I tried this experiment with other anacondas; always with the same result. The fact stood proven that the difference between an earl and an anaconda is that the earl is cruel and the anaconda isn't; and that the earl wantonly destroys what he has no use for, but the anaconda doesn't. This seemed to suggest that the anaconda was not descended from the earl. It also seemed to suggest that the earl was descended from the anaconda, and had lost a good deal in the transition."