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December 29, 2015

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Chatting may serve evolutionary need to bond

Dec. 29, 2015
Courtesy of Princeton university
and World Science staff

We think of chit­chat and small talk as the things peo­ple say to pass the time or kill an awk­ward si­lence. But new re­search sug­gests these idle con­versa­t­ions could be a so­cial-bonding tool pas­sed down from our ape-like an­ces­tors.

Sci­en­tists with Prince­ton Un­ivers­ity stud­ied ring­tailed lemurs, an­i­mals that are con­sid­ered among the more an­ces­tral forms of pri­mates—the ev­o­lu­tion­ary line­age that in­cludes hu­mans, apes and mon­keys.

Ring-tailed lemur (Le­mur cat­ta) (Pho­to: Ipek Ku­lah­ci, Prince­ton U.)


The study con­cludes that lemurs call to each oth­er es­sen­tially as a re­place­ment for mu­tu­al groom­ing, or clean­ing each oth­er’s fur, a wide­spread so­cial-bonding be­hav­ior among non-hu­man pri­ma­tes.

Lemurs vo­cal­ize to es­sen­tially “groom-at-a-distance” when they’re sep­a­rat­ed, said Ipek Ku­lahci, a co-author of the study pub­lished in the jour­nal An­i­mal Be­hav­iour. Ring­tailed lemurs liv­ing in groups mainly call and re­spond to the in­di­vid­u­als with which they have close rela­t­ion­ships and groom most of­ten, ac­cord­ing to the au­thors. 

“Our re­sults in­di­cate that when an­i­mals re­spond to each oth­er’s vo­cal­iz­a­tions, they are in fact al­so work­ing on main­tain­ing their so­cial bonds,” said Ku­lahci.

“By ex­chang­ing vo­cal­iz­a­tions, the an­i­mals are re­in­forc­ing their so­cial bonds even when they are away from each oth­er,” Ku­lahci said. “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.”

The find­ings could have im­plica­t­ions for how sci­en­tists un­der­stand the ev­o­lu­tion of pri­mate vo­cal­iz­a­tions and hu­man speech, said Asif Ghaz­an­far, Ku­lahci’s doc­tor­al ad­vi­sor, who par­ti­ci­pated in the work.

“Talk­ing is a so­cial lub­ri­cant, not nec­es­sarily done to con­vey in­forma­t­ion, but to es­tab­lish fa­mil­iar­ity,” he said. “I think these vo­cal­iz­a­tions are equiv­a­lent to the chit­chat that we do. Peo­ple think that con­versa­t­ions are like ex­chang­ing mini-lectures full of in­forma­t­ion. But most of the time we have con­versa­t­ions and for­get them when we’re done be­cause they’re per­form­ing a purely so­cial func­tion.”

Ex­ist­ing the­o­ries of lan­guage ev­o­lu­tion sug­gest that vo­cal ex­changes be­tween pri­ma­tes evolved with group size, he said. As group size in­creased, groom­ing to form so­cial bonds be­came too time con­sum­ing, so speech de­vel­oped to save time while still ex­press­ing fa­mil­iar­ity.

But Ghaz­an­far and col­leagues found that vo­cal­iz­a­tions oc­curred in­de­pend­ently of group size. The lemurs the re­search­ers stud­ied groomed more as their num­bers in­creased, but did­n’t nec­es­sarily vo­cal­ize more. These find­ings re­veal a di­rect con­nec­tion be­tween groom­ing—or fa­mil­iar­ity—and vo­cal­iz­a­tion, Ghaz­an­far said.

The researchers studied le­mur groups living at the Le­mur Cen­ter at Duke Uni­versity in North Caro­lina and on St. Cather­ines Island in Geor­gia.

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We think of chitchat and small talk as the things people say to pass the time or kill an awkward silence. But new research suggests these idle conversations could be a social-bonding tool passed down from our ape ancestors. Scientists with Princeton University studied ringtailed lemurs, animals that are considered among the more ancestral forms of primates—the evolutionary lineage that includes humans, apes and monkeys. The study concludes that lemurs call to each other essentially as a replacement for mutual grooming, or cleaning each other’s fur, a widespread social-bonding behavior among non-human primates. Lemurs vocalize to essentially “groom-at-a-distance” when they’re separated, said Ipek Kulahci, a co-author of the study published in the journal Animal Behaviour. Ringtailed lemurs living in groups mainly call and respond to the individuals with which they have close relationships and groom most often, according to the authors. “Our results indicate that when animals respond to each other’s vocalizations, they are in fact also working on maintaining their social bonds,” said Kulahci. “By exchanging vocalizations, the animals are reinforcing their social bonds even when they are away from each other,” Kulahci said. “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.” The findings could have implications for how scientists understand the evolution of primate vocalizations and human speech, said Asif Ghazanfar, Kulahci’s doctoral advisor, who participated in the work. “Talking is a social lubricant, not necessarily done to convey information, but to establish familiarity,” he said. “I think these vocalizations are equivalent to the chitchat that we do. People think that conversations are like exchanging mini-lectures full of information. But most of the time we have conversations and forget them when we’re done because they’re performing a purely social function.” Existing theories of language evolution suggest that vocal exchanges between primates evolved with group size, he said. As group size increased, grooming to form social bonds became too time consuming, so speech developed to save time while still expressing familiarity. But Ghazanfar and colleagues found that vocalizations occurred independently of group size. The lemurs the researchers studied groomed more as their numbers increased, but didn’t necessarily vocalize more. These findings reveal a direct connection between grooming—or familiarity—and vocalization, Ghazanfar said.