A FEATURE of language which was believed to be unique to humans has been found in monkeys鈥� calls too. It will cast doubt on the idea that people evolved complex language from scratch. But some researchers insist it has no such significance.
The set of rules known as syntax that link word order to meaning is something unique to humans, or so most scientists thought. But Klaus Zuberb眉ler at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, now claims to have identified syntax in monkey communication. He believes this strengthens the notion that language evolved much earlier than 200,000 years ago, the date of the earliest human fossils with vocal tracts. 鈥淭hat time frame is much too short to evolve something as important as language,鈥� he adds.
Zuberb眉ler observed groups of Campbell鈥檚 and Diana monkeys in Ta茂 Forest in the Ivory Coast, West Africa. When threatened, Campbell鈥檚 monkeys make different calls depending on the danger: one for an eagle and a different one for a leopard. The group then responds accordingly鈥攆or example, by ganging up on the leopard to prevent a surprise attack.
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But if a call is preceded by a 鈥渂oom鈥�, the group doesn鈥檛 react. Zuberb眉ler thinks this is used as a caveat when the caller is not certain of the threat, as though they are saying: 鈥淭here might be a leopard, but no need for immediate action.鈥�
When Zuberb眉ler played recordings of Campbell鈥檚 threat calls to Diana monkeys, they reacted with their own equivalent call. What鈥檚 more, they seemed to understand the 鈥渉edge factor鈥� introduced by the boom, since the same threat calls coupled with booms did not produce a response. Zuberb眉ler claims that since the boom changes the meaning of the subsequent call, it is following a basic syntactic rule.
But others disagree, pointing out that human language is far more complex. 鈥淭his is very much at odds with what syntax means in human language,鈥� says Marc Hauser, an expert in primate communication at Harvard University.
For instance, tungara frogs have a mating call that incorporates a basic whine, which can be followed by a 鈥渃huck鈥�. The chuck changes the meaning of the whine, and there is a consistent order. But no one calls this syntax, says Hauser.