Humans are not the only creatures on the planet with the ability to speak in syntax. A new study shows some forest-dwelling primates of Africa can combine calls into long vocal sequences. Further, they grammatically arrange words in a certain order to give them more meaning. This allows them to convey messages about social cohesion or incoming predators.
The study was carried out by researchers at the Ethologie Animale et Humaine research group, working alongside the universities of St. Andrews in Scotland and Cocody-Abidjan in Ivory Coast. And they were recently published on the website of the Proceedings of the National Academy of Sciences.
Researchers spent the past two years studying monkeys at Ivory Coast's Taï national park. They found that adult Campbell’s monkey males, (Cercopithecus campbelli campbelli,) use six alarm calls — "boom," "krak," "hok," "hok-oo," "krak-oo" and "wak-oo" — to further combine them into complex sentences.
The study focused on the loud calls of adult males, whose vocal repertory is very different from the females. The monkeys live in small groups of 10 or so individuals, comprised of an adult male, several adult females and their progeny. As the animals live in a habitat with limited visibility, it seems that they developed this vocal proto-syntax as their primary means of communication.
Campbell's monkeys also combine calls in order to convey different messages. It was determined that the monkeys modify a call sequence or the order of calls within a sequence to change messages. They can relay exact information about a predator, type of predator, (say, an eagle,) how the predator was detected, (they heard the eagle’s calls).
The calls can also include information about social events, such as encountering another group of the same species at territory boundaries. Not to mention, Campbell's monkeys might also combine sequences relaying different messages in order to convey a third message.
This study is important because it shows animal vocal communication as a precursor to human language.