New research on vocalizations of wild chimpanzees has demonstrated that their alarm calls have numerous hallmarks of intentional communication.

Many biologists consider non-human primate vocalizations to be a simple read-out of emotion 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 the open-access journal 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.

Dr Anne Schel and Dr Katie Slocombe from the University of York with colleagues studied wild chimpanzees living in the Budongo Forest Reserve in Uganda. They presented the 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.

The scientists 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 vocalisations and human language,” Dr Slocombe explained.

She added: “our results demonstrate that certain vocalisations 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.”

“Observing the chimpanzees reacting to the snake model was intriguing. 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,” Dr Schel said.

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Bibliographic information: Schel AM et al. 2013. Chimpanzee Alarm Call Production Meets Key Criteria for Intentionality. PLoS ONE 8 (10): e76674; doi: 10.1371/journal.pone.0076674