Characters: The Doctor.
Written For: Challenge 153: Cats And Dogs at dw100.
Spoilers: Tiny for New Earth and Gridlock.
Summary: Evolution means survival of the most adaptable.
Disclaimer: I don’t own Doctor Who, or the characters.
It’s always amused the Doctor that humans are so obsessed with pets; most families seem to have at least one, usually a dog or a cat. Dogs are pack animals, happy to follow whoever they consider to be their pack leader, and loyal to a fault. Cats, on the other hand, are independent creatures, often loners, and they do what they want to do, not what somebody else tells them they should.
Perhaps that goes some way to explaining why, in the future, dogs have remained unchanged while cats have evolved into an intelligent, sentient race in their own right.