British scientists have discovered that the putty-nosed monkey in Nigeria pictured above sometimes communicates by combining sounds into a sequence that has a different meaning from any of its component calls, an ability that was thought to be uniquely human.

Although many animals communicate with one another using calls that have a particular meaning — usually a warning signifying the presence of a certain predator — none has been known to combine these alarm calls into sequences similar to those of human language.

The findings suggest that the rudiments of syntax, a basic component of human language, may be more widespread among primates than is generally thought, and could ultimately shed light on the evolution of this most distinctly human of traits.

The putty-nosed monkeys, Cercopithecus nictitans, of the Gashaka Gumti National Park, have two main alarm call sounds. A sound known onomatopoeically as the “pyow” warns other animals against a lurking leopard, and a cough-like sound that scientists call a “hack” is used when an eagle is hovering near by.

Kate Arnold and Klaus Zuberbühler, of the University of St Andrews, have now observed the monkeys using these sounds in a new way. A particular sequence of pyows and hacks appears to mean something entirely different.

The monkeys live in groups consisting of a single adult male accompanied by several adult females and their young. When the male utters this “sentence”, consisting of up to three pyows followed by up to four hacks, it seems to be a command telling others to move,generally to find safer, less exposed terrain.

They use the signal not only when predators are around, but also during ordinary activities such as foraging. It seems to mean “let’s get out of here”.

The research is published today in the journal Nature. Dr Arnold said: “These calls were not produced randomly and a number of distinct patterns emerged. One of these patterns was what we have termed a pyow-hack sequence. This was either produced alone or inserted at certain positions in the call series.

“Observationally and experimentally we have demonstrated that this sequence serves to elicit group movement in both predatory contexts and during normal day-to-day activities such as finding food sources and sleeping sites.

“The pyow-hack sequence means something like ‘let’s go’ whereas the pyows by themselves have multiple functions and the hacks are generally used as alarm calls.”

Dr Arnold added: “The implications are that primates, at least, may be able to ignore the usual relationship between an individual call and any meaning that it might convey under certain circumstances.”

Dr Zuberbühler said: “To our knowledge, this is the first good evidence of a syntax-like natural communication system in a non-human species.”

A separate study published in Nature today has shed further light on human evolution, suggesting that early human ancestors may have interbred with the forerunners of chimpanzees for hundreds of thousand years after the two species branched out from their shared family tree.

A comparison of the genetic codes of humans and chimps has revealed that the split between the two probably occurred much later than is generally thought, and in a much more complicated fashion. According to previous estimates, the last common ancestor of both species lived about 7 million years ago. The genetic study, however, sets 5.4 million years ago as the most likely date for the split, and shows that it cannot have happened more than 6.3 million years ago.

The analysis also indicates that after the split both branches initially interbred, before they ultimately diverged into distinct species.

“The genome analysis revealed big surprises, with major implications for human evolution,” Eric Lander, of the Broad Institute at the Massachusetts Institute of Technology, said.

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