The External Nose

by Monica Bennett about a year ago in evolution

What We Know and What We Don't

The External Nose

Some are tiny and button-like, some look like a ski jump, others have bumps in the middle or wide nostrils, but they are all sone of the biggest mysteries in evolution. Why do we have an external proboscis that protrudes from our faces? This should be an easy question to find an answer to, but nothing could be further from the truth. A lot of research has been done on the shape of the nose and that is determined by the climates our ancestors lived in. In a paper published in PLOS Genetics, "Investigating the case of human nose shape and climate adaptation" byArslan A. Zaidi, Brooke C. Mattern, Peter Claes, Brian McEvoy, Cris Hughes, Mark D. Shriver, the authors put forth the idea that wide noses with larger nares are selected for in warm, wet environments, and long, narrow noses are selected for cold, dry climates. They examined nose measurements from a total of 140 women who were of West African, East Asian, northern European or South Asian ancestry. One doesn't have to leave Africa to find exceptions to their findings. Northern Ethiopians and Eritreans have narrow noses, and genetics have shown little admixture from Europeans or Arab groups, and instead have a common cluster of Y chromosome E3b, a haplogroup unique to the horn of Africa. Then there are the Fulani people of West Africa. They live in a warm, humid climate, but have narrow noses. This is the largest tribe in Africa, and they do not fit the mold these researchers have determined.

Ethiopian Woman

Another glaring inconsistency is the Neanderthal. If they are cold-adapted, why do they have such wide noses? This study on nose shape does not take into consideration the Inuits, who have wide noses but live in cold climates. The authors claim that a narrower nose warms the cold air by adding more turbulence to an inhalation. However, Takeshi Nishimura at Kyoto University, Japan, and his colleagues argue that both chimps and macaques perform circulation through the nose better than we do. They tested three different air types; hot/humid, cold/dry, and hot/dry. In each case, the nonhuman primates conditioned the air better. These authors nix the climate based nose. In a statement from CARTAby Robert Franciscus, "...the precise role of the external nose independent of the internal nasal cavity in terms of conditioning respiratory air and ameliorating moisture loss is incompletely understood."

Downward Pointing Nostrils

None of this explains why our noses project from our faces. There are researchers who say the big brain and smaller teeth of modern humans forced the nose to protrude because of limited space on the face but that just doesn't seem logical. Why didn't the flat nose just get smaller instead of projecting? There is one answer to all of this that might offer an answer. If we lived at the coast, an idea gaining in popularity, then we would have spent time in the water. Our noses have a built-in umbrella that helps keep water out. We can also close off our noses with an internal muscle. This is something water mammals have in common. Otters, beavers, polar bears, seals, and hippos can do it too. Their nostrils do not face downward, but our downward facing noses allows the air in our nostrils to block the water from coming in while we briefly lowered our heads while gathering food in the water. While we were not water mammals per say, we spent enough time in the shallows to allow for selection of a better nose for life on the shore. We developed a nose that would permit waterproof gathering with heads bent in the water, a streamlined acquisition for swimming, and free hands for both. If you search Scholar Google, you'll find absolutely zero research on the external nose. Try the subscription services such as DeepDyve or Jstor, and it's the same thing. Why do our noses protrude? These are the available choices, at present. The only one that makes sense is the waterside theory. The actual shape of the human nose may be the result of genetic drift or sexual preference or both.

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Monica Bennett

I am a retired high school and college teacher. I have taught forensics, biology, chemistry, ecology, and Earth science.. Long Island has been my home for 60 years.

See all posts by Monica Bennett