"“And you know what I think about evolution, Mister Stibbons. If it happens, and frankly I’ve always considered it a bit of a fairy story, it has to happen fast. Look at lemmings, for one thing.” “Lemmings, sir?” “Right. The little blighters keep chargin’ over cliffs, right? And how many have ever changed into birds on the way down, eh? Eh?” “Well, none, of cou—” “There’s my point,” said Ridcully triumphantly. “And it’s no good one of them on the way down thinking, ‘Hey, maybe I should waggle my claws a bit,’ is it? No, what it ought to do is decide really positively about growing some real wings.” “What, in a couple of seconds? While they’re plunging towards the rocks?” “Best time.” “But lemmings don’t just turn into birds, sir!” “Lucky for them if they could, though, eh?” (p. 107)"