These monkeys smile like us and it could say a lot about the origin of laughing

Researchers at the Primate Research Institute at Kyoto University in Japan filmed smiles in sleeping Japanese macaques, possibly revealing more about the origin of smiling and laughter in humans. Until now, we thought the smiles, called “spontaneous smiles,” only happened in humans and chimpanzees. They’ve never before been observed in more distantly-related primates.