Monkey Talk Could Show Roots of Human Language

LONDON (Dec. 11) -- It's long been known that dolphins, chimps, birds and a herd of other animals use a variety of sounds to communicate simple messages -- "Go away" and "Please breed with me" being favorites. But what's always separated animals' cries, squawks and clicks from human chatter is syntax. We can piece together different sounds to create new meanings, like when you add the prefix "un-" to "conscious" or the suffix "-less" to "charm." Animals, it was traditionally thought, couldn't.

Those assumptions have been shattered by a new study in the U.S. journal Proceedings of the National Academy of Sciences. A scientific team led by psychologist Klaus Zuberbühler of Scotland's University of St. Andrews has discovered that Campbell's monkeys -- inhabitants of Tai National Park in the West African nation of Ivory Coast -- use basic grammatical rules, making them one of the planet's most advanced communicators. And as Campbell's monkeys and humans split from a common ancestor some 30 million years ago, these findings could offer clues as to how our own language was constructed.

Zuberbühler, who has studied Campbell's monkeys for the past decade, has previously recorded how the tree dwellers use several distinct calls in different contexts. A cry of "krak" indicates a leopard is in the area. If a primate-eating crowned eagle is spotted circling the forest canopy, they holler "hok." And "boom" means, "Let's move."

However, on further analysis, Zuberbühler's team noticed that the male monkeys sometimes bolted an "-oo" to the end of their "kraks" and "hoks," changing their original meaning. A cry of "krak-oo" doesn't simply caution, "Watch out for the leopard." It becomes a warning that can be applied to several predators, but one only used in certain situations: when the monkeys can hear but not see a hunter, or when a neighboring troupe of Diana monkeys makes an alarm cry.

Similarly, "hok-oo" signifies a more general kerfuffle in the canopy, such as the presence of neighboring groups of monkeys, or the sighting of another bird of prey. "What is interesting is that the same acoustic modifier is being used for these calls," Zuberbühler told BBC News. "That is really analogous to using a suffix in human language."

That wasn't the end of the savvy simians' linguistic tricks. By combining two booms with a series of "krak-oos" ("Boom boom krak-oo krak-oo krak-oo"), the Campbell's monkeys developed a word far removed from its component parts. That combination of cries is the equivalent of "Timber!" -- watch out for a falling tree.

The next stage of Zuberbühler's research will see him play back his recordings to the Campbell's monkeys, to find out whether he has correctly interpreted their unique calls. If they react as expected, then these smart-speaking monkeys will truly be jungle VIPs.