Different in degree or kind: our nose (Introduction)

by David Turell , Monday, March 28, 2016, 02:41 (3163 days ago) @ dhw

We are the only primate with a nose like ours:-https://www.newscientist.com/article/2082274-the-evolution-of-the-nose-why-is-the-human-hooter-so-big/-"It's an evolutionary mystery that's literally as plain as the nose on your face. Why did our ancestors develop a prominent protruding nose when most primates have flat nasal openings?-"A new study suggests that our unusual nose may have gained its shape simply as a by-product of other, more important changes in the structure of our face - although other researchers insist that some human noses have been directly shaped by natural selection.-"One of the many functions of the nose and nasal cavity is to act as an “air conditioner”. Together, they make sure that the air an animal breathes in is made warm and humid enough to avoid damaging the delicate lining of the lungs.-"But Takeshi Nishimura at Kyoto University, Japan, and his colleagues argue that the human nose performs this job poorly. 
 
"They took scans of the nose and nasal cavity of six human volunteers, four chimpanzees and six macaques. Then, using computers, they modelled the flow of inhaled air through the nasal passages.-"Finally, they calculated how efficiently these flow patterns would condition three different air types: cold and dry, hot and dry, and warm and wet.-"The results suggest that the nasal passages of chimps and macaques condition inhaled air much more effectively than our nasal passages do. In fact, even when the researchers artificially manipulated the computer-generated human noses to look more like the flat ones of chimpanzee, the air-conditioning performance didn't improve.-***-"The hominin skull underwent a dramatic reorganisation with the appearance of true humans from our Homo genus between 2 and 3 million years ago. Brains grew and faces became relatively smaller to make room - and it is possible that the nose and nasal cavity were forced into their current shape to accommodate these changes.-"Fortunately, given that the climate fluctuated in Africa around the time that true humans first appeared, making good air conditioning vital, other parts of the human airways changed too. This may have made up for any inefficiency in the nose and nasal cavity, allowing humans to fully condition the air they inhaled. In particular, the pharyngeal region of the throat - which is much longer in humans than in other primates - may have begun to lengthen at this time.-"Our long pharynx is often linked to our ability to talk, but Nishimura says that it also plays an important role in conditioning inhaled air. (my bold)-"Despite the new findings, Todd Rae at the University of Roehampton, UK, says we shouldn't write off the idea that noses adapted to the climate that their owners inhabited.-“'There is a general trend for people in the tropics to have a wide nasal aperture,” he says. “Europeans, on the other hand, have a narrower aperture, which has been assumed to be an adaptation for living in colder climates.”-"Narrow nostrils, the thinking goes, create more turbulence in the inhaled air, which increases the level of heat and moisture exchange between the air and the tissue covering the wall of the nasal cavity.-"The Neanderthals are an apparently glaring exception to this rule - they lived in cold Europe yet had large wide noses. But Rae and his colleagues have argued that this might be because Neanderthals actually evolved and adapted in relatively warm and humid conditions before later moving into Europe."-“If you don't assume that [Neanderthals] were cold-adapted, the shape of the aperture isn't confusing, because that was simply inherited unchanged from their common ancestor,” Rae says."-Comment: the elongated pharynx, which allowed a dropped larynx, definitely was an arrangement to allow speech. There is no dispute here. Narrow nose seems not entirely clear as to purpose, since it varies from tropics to colder zones.