Researchers taping calls of the putty-nosed monkey in the forests of Nigeria may have come a small step closer to understanding the origins of human language.
The researchers have heard the monkeys string two alarm calls into a combined sound with a different meaning, as if forming a word, Kate Arnold and Klaus Zuberbühler report in the current issue of Nature.
Monkeys are known to have specific alarm calls for different predators. Vervet monkeys have one call for eagles, another for snakes and a third for leopards. But this seems a far cry from language because the vervets do not combine the calls into anything resembling words or sentences.
The putty-nosed monkeys have a "pyow" call meaning there are leopards about and a hacklike sound to warn of the crowned eagle. The "pyow" calls attention to a leopard on the ground.
When hearing the "hack" sound, a monkey tends to freeze because movement would betray its position to an eagle.
Dr. Arnold and Dr. Zuberbühler, zoologists at the University of St. Andrews in Scotland, noticed that adult male monkeys in each troupe were combining the "pyow" and "hack" calls.
Playing back a "pyow-hack" call to see how the monkeys interpreted it, the zoologists found it made the troop leave the area.
Language is a surprising faculty because it seems to pop up almost out of nowhere in the human lineage, instead of evolving in steady stages.
Researchers studying monkeys and apes have learned that they possess all the basic apparatus needed to make and analyze sounds. But the nonhuman primates did not seem to possess either of the two combinatorial features of language, those of combining discrete sounds into compound words, and of stringing words together under rules of syntax.
Dr. Zuberbühler said that he and Dr. Arnold had not observed anything resembling syntax, but the putty-nosed monkeys, Cercopithecus nictitans, "combined two types of utterances according to a rule and the combination takes on a novel meaning," a procedure perhaps analogous to forming a word from two sounds.
Marc Hauser, an expert on animal communication at Harvard, said that the observation was very interesting but that stricter criteria should be applied before assuming the combination of alarm calls was similar to the way people combined sounds into words.
"Because there is no evidence that the calls are words or even wordlike, the connection to language is tenuous." he said.