Non-parents expand the range of their facial expressions in caring for infants, research on primate alloparenting finds. The study shows the ability, among non-relatives, to both decipher facial expressions and to be attuned to others’ emotional states, revealing the evolutionary nature of communication. The research, which appears in the journal Evolution, focuses on the relationship between alloparenting, or infant care by non-parents, and the adoption of detailed facial expressions across more than 30 species of primates. “Our results confirm previous work indicating that facial expressions facilitate communication between individuals living in larger social groups,” says study author Paola Cerrito, a doctoral candidate in New York University’s department of anthropology and College of Dentistry. “But, this is the first study to demonstrate that the frequency of infant care by non-parents further predicts the ability to produce complex facial expressions across primate species.”