Scientists who study the evolution of language say that wild chimpanzees have a more complex communication system than previous research has shown. Researchers say the animal uses more than ten types of calls that can be combined into hundreds of different orders or sequences.
The study team made 4,800 call recordings produced by members of three groups of chimpanzees that live in the Taï National Park in Côte d’Ivoire. The park is one of the last major areas of ancient rainforest in West Africa and is home to many species of plants and animals.
Chimpanzees, along with bonobos, are the closest living relatives of humans. They are intelligent and very social. Chimpanzees make and use tools and can learn a small amount of human sign language.
Scientists have long known that chimpanzees use different calls, or vocalizations, in nature. But the new study offered a deeper understanding of their communication.
Cédric Girard-Buttoz was the main editor of the study published in the publication Communications Biology.
Girard-Buttoz said of the cries of chimpanzees: “It is not a language but it is one of the most complex forms of communication described in a non-human animal.”
The types of calls included what the researchers called a growl, a gasping growl, a hoo sound, a gasping hoot, a barking sound, a gasping bark, a gasp, a cry, a gasping cry, a whine, a breathless roar and the non-smack of vocal lips and raspberry sounds. The researchers determined that these types of calls were used in 390 different orders or sequences.
“In general, ‘pant grunt’ and ‘pant hoot’ are the most commonly used calls in these sequences,” Girard-Buttoz said.
The order in which the chimpanzees uttered the calls seemed to follow rules, although the study did not include any insights into possible meanings.
Girard-Buttoz said the study was important because it shows the beginning of communication that could have been the starting point for the evolution to “syntax in our language”.
Syntax is the way words are put together to form sentences or complete sentences.
Researchers want to know if the sequences communicate broader meanings. They have suspicions about the possible meanings of certain vocalizations.
Girard-Buttoz said researchers need to “explore in detail” the situations surrounding these calls. He added that researchers need to do “proofreading experiments to see if the suspected meaning matches the behavioral response of chimpanzees when they hear the call.”
Researchers don’t know if chimpanzee vocal communication is similar to the beginnings of language in the history of human evolution. Humans and chimpanzees share one thing in common ancestor but split into separate evolutionary families perhaps 7 million years ago.
I am John Russell.
Will Dunham reported this story for Reuters. John Russell adapted it for VOA Learning English.
words in this story
evolution -nm a process of slow change and development
vocalization -not. act of producing sound with the voice
proofreading – nm action of making heard or reviewing recorded sounds or images
ancestor -not. an animal of the past from which a modern animal developed; one of the persons from whom a person is descended