Hutton gave the example that where dogs survived through "swiftness of foot and quickness of sight... the most defective in respect of those necessary qualities, would be the most subject to perish, and that those who employed them in greatest perfection... would be those who would remain, to preserve themselves, and to continue the race".
Hutton deu como exemplo que cando os cans sobreviviron a través de "a rapidez das patas e a agudeza visual... os máis carentes das calidades necesarias, serían os máis suxeitos a perecer, e que aqueles que as utilizaran con maior perfección... serían os que quedarían, para conservarse, e continuar a carreira".