For centuries, humans have marveled at the sounds and calls of the animal kingdom, wondering if deeper meanings lurked beneath the chatter of birds, the growls of predators, or the hoots of primates.
Now, a groundbreaking study suggests that Campbell’s monkeys (Cercopithecus campbelli)—small primates native to western Africa—may possess a structured form of communication remarkably similar to human language.
A Breakthrough in Animal Linguistics
Researchers have long suspected that certain primates communicate with more than just instinctive calls.
However, the latest research, led by Philippe Schlenker of France’s National Centre for Scientific Research and New York University, provides compelling evidence that these monkeys utilize a rudimentary linguistic system, complete with roots, suffixes, and contextual meanings—a feature once thought to be unique to humans.
The key to this discovery? A single word: “krak.”
The Importance of ‘Krak’
In the Ivory Coast’s Tai Forest, Campbell’s monkeys use the call “krak” to signal the presence of a leopard, a notorious predator in the region.
Meanwhile, “hok” is used to warn of an eagle soaring overhead.
Both calls serve as alarm signals, warning fellow monkeys of impending danger.
However, researchers made a startling discovery when they turned their attention to Tiwai Island in Sierra Leone—an area where leopards do not exist.
On the island, the same species of monkey still used “krak”—but rather than referring specifically to leopards, the call became a general alarm signal for any threat, including eagles.
This discovery raised an intriguing question: Do these monkeys modify their language based on their environment?
A Language More Complex Than Expected
For years, scientists believed that primate calls were simply reflexive responses—fixed and unchanging.
But the context-dependent nature of krak challenges this assumption.
Monkeys on the mainland differentiate threats with greater specificity, using variations such as:
- “krak-oo” – A lower-intensity warning for minor ground threats.
- “hok-oo” – A similar soft warning for aerial threats.
- “boom” – A reassuring call signaling that the danger has passed.
On Tiwai Island, however, this complexity disappears.
With no leopards to worry about, the monkeys use “krak” indiscriminately for all threats. Why?
The answer may lie in a linguistic concept known as implicature—a subtle, often unspoken layer of meaning found in human speech.
The Hidden Meaning in Monkey Calls
Human language relies on choosing the most informative words based on context.
For example, if someone tells you a task is “possible,” it usually implies that it is not certain—otherwise, they would have said so.
This subtle inference, known as implicature, shapes much of human communication.
Schlenker’s team believes Campbell’s monkeys use the same logic.
On the mainland, where there are both leopards and eagles, saying “krak” implies “not hok” and “not krak-oo”—meaning the threat must be a leopard.
On the island, where this distinction isn’t necessary, krak simply means “danger.”
What This Means for the Future of Animal Linguistics
These findings suggest that primate communication is more sophisticated than previously thought.
Rather than issuing randomized alarm calls, Campbell’s monkeys appear to construct meaning through the interplay of sounds, context, and social cues—a feature that mirrors the evolution of human language.
Schlenker envisions this research as the foundation for a new scientific field: “primate linguistics.”
By applying linguistic methodologies used in human language studies to the calls of primates, researchers may unlock an entire hidden world of animal communication.
Skepticism and the Road Ahead
Not all scientists are fully convinced.
Arik Kershenbaum, a zoologist at the National Institute for Mathematical and Biological Synthesis, warns that while the study presents a strong internal logic, it still relies heavily on correlation.
Without direct experimental proof, the hypothesis remains speculative.
That said, the implications are exciting.
If primates truly structure their calls in ways similar to human language, it blurs the line between animal communication and linguistic expression.
Are we witnessing the first glimpses of a deeper primate grammar?
Could other animals, from dolphins to elephants, have equally intricate systems of communication waiting to be deciphered?
A Step Closer to Understanding Animal Minds
What once seemed like simple monkey chatter now appears to be part of a structured, meaningful form of communication.
While Campbell’s monkeys may not be composing sentences, they are certainly conveying layered, context-dependent messages—a trait we previously thought was exclusive to humans.
With further study, we may one day bridge the gap between human and animal language, offering a new perspective on how intelligence and communication evolve in the natural world.
For now, though, one thing is clear: when a Campbell’s monkey says “krak,” it means far more than we ever imagined.
Source: Scientific American, Phys.org
