Are humans the only creatures that can smile?

Question

Are humans the only creatures that can smile?

Answer 1

My dog smiles, when I wag my tail!

Answer 2

Other animals CAN smile, however, humans are the only animals to smile when happy. When another animal such as a baboon or other monkey smiles it is typically a sign of fear or aggression, thus it is a good idea to stir clear of other animals when you observe them smiling at you.