How is your nose? A new analysis on how a human nose can condition ambient air gives us fascinating information: primates fare better than we do.
Human evolution has indeed come a long way. An obvious indication is the shape of our head, which now features a flatter face, a bigger skull to accommodate a bigger brain, and a protruding nose.
But how does this change - say, our nose - compare to that of primates and early hominins?
To answer the question, Kyoto University researchers led by Takeshi Nishimura scanned the nasal passages of a human, a macaque and a chimpanzee. The team analyzed how air conditioning happens in the nose using computational fluid dynamics and 3D models. They also tried to simulate different temperature and humidity conditions like hot, dry, or wet to see how they impact nasal conditioning.
"[T]he airflow direction in the nasal cavities of chimpanzees and macaques differs in some key regions from that in humans," said the study, published in PLOS Computational Biology. The air flows in a horizontal pattern among primates and upward and curved among humans.
The differences mean that compared to humans, primates already can adjust the temperature and humidity of ambient air while it was still halfway in their nasal cavity even in extreme conditions.
This data is significant since one of the functions of the nose is to adjust the humidity and temperature of breathed air according to the internal parameters of the lungs. Otherwise, with poor conditioning, the organ becomes damaged over time, increasing the risk of different respiratory problems, and even premature death.
Evolution, therefore, has somehow "impaired" the nasal conditioning system of our ancestors when compared to the performance of the early hominins, whose nasal passage was similar to primate's.
But if our ancestors could not condition air effectively, how were they able to survive the extreme climate conditions when they went out of Africa and settled in Europe and Asia?
The answer is morphology.
"When human skulls flattened and elongated vertically, not only did it change the dimensions of the nasal cavities, but also the oral and pharyngeal cavities. The morphological changes to the skull caused the tongue to be pushed down toward the pharynx, and thus lengthening the pharyngeal cavity," the PLOS blog post said.
This means that the pharynx reinforces the work of the nasal passage in conditioning the air before it reaches the lungs. As an evolutionary bonus, these physical changes may also be responsible for the development of speech as the vocal cords have now become more complex and can produce different types of sounds.
Photo: Quinn Dombrowski | Flickr
