Researchers say the alarm calls of wild chimpanzees have the hallmarks of intentional communication.
Many scientists consider non-human primate vocalizations to be a simple read-out of emotion (e.g., alarm calls are just an expression of fear) and argue they are not produced intentionally, in sharp contrast to both human language and great ape gestural signals.
This has led some scientists to suggest that human language evolved from a primitive gestural communication system, rather than a vocal communication system.
The new study, published in PLOS ONE, challenges this view and shows that chimpanzees do not just alarm call because they are frightened of a predator; instead, they appear to produce certain alarm calls intentionally in a tactical and goal directed way.
In Uganda, the researchers presented wild chimpanzees with a moving snake model and monitored their vocal and behavioral responses. They found that the chimpanzees were more likely to produce alarm calls when close friends arrived in the vicinity. They looked at and monitored group members both before and during the production of calls and critically, they continued to call until all group members were safe from the predator.
Together these behaviors indicate the calls are produced intentionally to warn others of the danger.
“These behaviors indicate that these alarm calls were produced intentionally to warn others of danger and thus the study shows a key similarity in the mechanisms involved in the production of chimpanzee vocalizations and human language,” says study co-leader Katie Slocombe, of the psychology department at the University of York.
“Our results demonstrate that certain vocalizations of our closest living relatives qualify as intentional signals, in a directly comparable way to many great ape gestures, indicating that language may have originated from a multimodal vocal-gestural communication system.”
Anne Schel, also of York’s psychology department and who co-led the study, says it was intriguing to watch the chimps react to the snake model. “It was particularly striking when new individuals, who had not seen the snake yet, arrived in the area: if a chimpanzee who had actually seen the snake enjoyed a close friendship with this arriving individual, they would give alarm calls, warning their friend of the danger.
“It really seemed the chimpanzees directed their alarm calls at specific individuals.”
The research team worked with wild chimpanzees at the Sonso field site of the Budongo Conservation Field Station in Budongo Forest Reserve in Uganda. The study involved other researchers from Budongo Conservation Field Station, the University of Zurich, Harvard University, the University of Neuchâtel, and the University of St Andrews.
Source: University of York