The #1 source for news about monkeys and apes

[Josh Greenman <joshg1973 AT yahoo.com>]

http://news.bbc.co.uk/2/hi/science/nature/4110977.stm

Monkey vocal ability investigated 

Diana monkeys possess a complex vocal tract whose shape can be adjusted to 
articulate
sophisticated sounds - just as humans do, scientists report. 

Non-human primates were thought to have vocal tracts resembling simple tubes 
incapable of
sophisticated articulation. 

But a British-US-German team reports in the Journal of Human Evolution that 
the alarm
calls of Diana monkeys would be impossible without a complex tract. 

It says the finding may shed light on how and when human speech evolved. 

It is possible that some of the proto-structures in the throat required for 
talking were
already present in our primate ancestors millions of years ago, the 
researchers argue. 
Good vibrations 

The latest results support acoustic analysis showing Diana monkey calls could 
not be
produced by a simple vocal tract. 

But this does not mean the animals are capable of anything more complex than 
the calls
they produce in the wild. 

The work was carried out by scientists at the University of St Andrews, UK; 
Humboldt
University in Berlin, Germany; and the Baltimore Zoo in Maryland, US. 

The researchers claim it is the first time both acoustic and anatomical data 
have
supported the presence of a non-uniform vocal tract in a non-human primate. 

"Previous models of animal sound production always assumed the vocal tract 
was like a
uniform tube. This explained why a lot of animal vocalisations had a very 
simple acoustic
structure," said Dr Klaus Zuberbühler, from St Andrews. 

"The human vocal tract is different because it consists of various tubes of 
different
sizes. This explains how we can produce such a range of different sounds that 
are
important for speech." 

X-ray inspection 

The team X-rayed the vocal tracts of three adult Diana monkeys (two male, one 
female)
from Baltimore Zoo and dissected the carcass of another which had died at the 
zoo. 

They used the results to generate a computer model that simulates the 
patterns observed
in the vocalisations of Diana monkeys. 

"With Diana monkey calls, it is clear there must be at least three different 
tubes to be
able to produce the acoustic patterns they make," said Dr Zuberbühler. 

"The suggestion is that they can change the size of these tubes to produce 
the sounds
they do. This is in some senses equivalent to how speech production takes 
place [in
humans]." 

These tubes are thought to be formed by constrictions at different sections 
along the
monkeys' vocal tract. 

Dr John Coleman, of the phonetics laboratory at Oxford University, UK, said 
he was not
surprised by the findings. 

"Just looking at the human vocal tract and other animals, it's quite frequent 
for
non-human primates to have quite complex vocal tracts. Chimpanzees in 
particular have
more complex vocal tracts than human beings," he said. 

Dr Zuberbühler said his team was now investigating whether the case found in 
Diana
monkeys was also true for chimpanzees, our closest animal relatives.