PRINCETON, NEW JERSEY—Scholars have speculated that human ancestors used grooming each other as a way to form social bonds until group sizes increased and it became too time consuming. Ipek Kulahci of Princeton University and her colleagues have observed that the ring-tailed lemurs living at Duke University’s Lemur Center and on St. Catherines Island, Georgia, groom each other as a means of social bonding, but use vocalizations to stay in touch with those individuals that they groomed the most frequently, independent of group size. “By exchanging vocalizations, the animals are reinforcing their social bonds even when they are away from each other,” Kulahci said in a press release. And, when the researchers played recordings of lemur calls to the group, only the lemurs that shared a close grooming relationship with the individual that made the call responded. “This social selectivity in vocalizations is almost equivalent to how we humans keep in regular touch with our close friends and families, but not with everyone we know,” she explained. To read about ancient languages, go to "The Wolf Rites of Winter."