Even if the phenotypical appearance of a nose is based on our parents’ genes, researchers now claim that our ancestors’ local climate adaptations are what provided it with its shape.
It is known that the shape of the nose varies depending on race and ethnicity, but the reason behind these variations remained unclear until recently.
The biggest obstacle was that human populations have separated and come together many times throughout history, making it nearly impossible to determine the primal origin of genetic-based traits.
Your ancestors’ climate shaped your nose
To discover more about how evolution had its way through humans, researchers from Penn State University surveyed 2,637 individuals, with people from Europe, South Asia, East Asia, and West Africa. They were modeled in 3D, and the research team examined their noses, including the width of the nostrils, the distance between each other, the height of the nose, its ridge’s length, and the overall area of the nostril.
Researchers noted that one of the primary functions of the nose is to warm the air that comes in, putting it at body temperature, and then saturating it with water vapor before it reaches the respiratory tract. This occurs 90 percent of the times, making the nose the major conditioning structure in the respiratory tract. This goes alongside the mucus on the nose trapping particles and restricting them from reaching the respiratory tract.
The air passes through the turbinates, which its walls are filled with blood vessels and mucus-producing cells. Ona related note, the conditioning process has been shown to depend on how the nose is shaped.
Many studies reached the conclusion that the nose is shaped by how the skull is formed, but in some cases, it was determined that nose morphology exceeded neutral expectations, which suggests that there may be other factors at hand when it comes to nose shape.
Researchers discovered a variable for accelerated divergence to test how certain aspects of nose shape differ across populations. Each comparison between subjects yielded a Qst variable that the team was able to compare to find a middle ground in exactly how different the nose of two individuals are.
“People have thought for a long time the difference in nose shape among humans across the world may have arisen as a result of natural selection because of climate. As we become more of a global community, as we move around the world, we are going to be encountering climates that we are not adapted to,” stated Arslan Zaidi, co-author of the study, according to The Guardian.
Based on previous studies that suggest nasal aperture and nasal cavity are related with climate variables including temperature and humidity, researchers took into account these climatic factors when making the comparisons. Each was assigned a climate value that was theoretically their ideal “ancestral” environment. The result was a strong relationship between skin pigmentation, nasal cavity width, and several other factors. For example, individuals from warm and humid climates tended to have wider nostrils, while those from cold and dry climates tended to have narrower nostrils.
Source: PLOS Genetics