A study involving Koko, known to be the most intelligent gorilla in the world, suggests that humans may not be the only primate with speech capabilities.
Researchers found that Koko's species can also learn new vocal and breathing-related behaviors, which defy earlier beliefs about the communication abilities of gorillas.
Marcus Perlman, from the University of Wisconsin-Madison said that scientists traditionally think that apes have extremely limited vocal abilities with no ability to voluntarily control vocalization. The animals are also thought to be incapable of learning new vocalizations beyond the confines of their species' repertoire.
For the study, which was published in the journal Animal Cognition on July 3, Perlman's team looked at 71 hours of video that showed Koko interacting with scientists and found that the gorilla used nine different learned behaviors that needed control over breathing and vocal activities.
The researchers observed that Koko would blow a raspberry when she wants a treat. She also played wind instruments, mimic conversation by chattering wordlessly into a fake telephone, blow her nose into a tissue and cough on demand, an impressive behavior for a gorilla since this requires her to close off her larynx.
Perlman said that although the gorilla does not produce pretty and periodic sound whenever she performs these behaviors just as humans do when they speak, Koko can control her larynx enough for her to produce a controlled grunting sound.
The behavior exhibited by the gorilla was voluntary and appeared to be the result of living with humans for most of her life. Koko has spent more than 40 years living with humans at The Gorilla Foundation and has been immersed with humans since she was six months old.
Scientists said that the behavior shown by Koko was surprising since it is generally believed that apes cannot control their vocalizations or breathing.
"We suggest that vocal learning and the ability to exercise volitional control over vocalization, particularly in a multimodal context, might have figured relatively early into the evolution of language, with some rudimentary capacity in place at the time of our last common ancestor with great apes," Perlman and colleagues wrote in their study.
The behavior exhibited by Koko may be impressive but it is unlikely that Koko and other gorillas would learn to "speak" to each other though the researchers said that this may possibly happen in a very distant evolutionary future.
"The groundwork is there for apes to learn new communicative behaviors ... and they appear to have some ability to transmit these behaviors through social learning and even transmit the behaviors across generations," Perlman said.
Photo: Hjalmar Gislason | Flickr