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.
The study observed seven newborn Japanese macaques, all of which displayed spontaneous smiles at least once. The results suggest that smiling and laughter may have origins much further back in evolutionary history than previously believed.