The Neanderthal’s huge nose is a fluke of evolution, not some grand adaptation, research suggests.
The Neanderthal nose has been a matter of befuddlement for anthropologists, who point out that modern cold-adapted humans have narrow noses to moisten and warm air as it enters the lung, and reduce water and heat loss during exhalation.
Big noses tend to be found in people whose ancestors evolved in tropical climates, where a large nasal opening helps cool the body.
But Neanderthals go against this trend, says Tim Weaver, a palaeoanthropologist at the University of California, Davis, who was not involved in the study.
“They were living in the glacial environment of Europe, colder than it is today, for most of the time,” he says. “So it’s sort of been an anomaly. Why do they have these wide nasal apertures?”
The traditional answer has been that Neanderthals have a big nose because they have a big mouth and a wide jaw, useful for ripping apart tough food, says Nathan Holton, a paleoanthropologist at the University of Iowa.
“People have tried to explain the Neanderthal face as designed to produce high levels of bite force and trying to explain the rest of a wide nasal breath as part of a larger tend,” he says.
To put this theory to the test, he and University of Iowa colleague Robert Franciscus, measured facial dimensions in dozens of Neanderthals and humans, ancient and modern.
By correlating changes in the size of nose width, the distance between canine teeth, and other features, the researchers could determine whether or not big mouths went with big noses.
Holton and Franciscus found a slight link between nose and mouth, but not enough to explain Neanderthal noses. However, another measurement – the degree to which the face juts forward – seemed a better match for nose width, Houlton says.
“If you want to change the breadth of the nose, you change the degree of facial projection,” he says.
Measurements in modern humans support this theory. By age 12, a child’s mouth has grown to its adult size, whereas the nose and facial projection continue to grow well into teenage years, Holton says. Recent research suggests that Neanderthals matured at the same rate as humans.
Fortunately for Neanderthals, their inner noses were narrower than the openings suggest, and therefore well adapted to bone-chilling winters.
Why, then, do Neanderthals have faces that jut further out than humans? “They had them because earlier hominids had them,” Houlton says.
He laments the tendency of some anthropologists to “atomise the body”, and explain each of its part as an exquisite adaptation to an environment. Selection for strong jaws and teeth has been a favourite explanation for other Neanderthal facial features, as well as nose size.
“There’s no real good evidence to say that Neanderthals are producing these high levels of bite force to begin with,” he says.
Weaver agrees. “A lot of these anatomical differences are probably more likely due to these chance changes,” he says.
Journal reference: Journal of Human Evolution (DOI: 10.1016/j.jhevol.2008.07.001)
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