Tuesday, August 23, 2011
Noses and race
Researchers in Germany have shown that individuals from cold, dry climates, such as Greenland or Siberia, had higher and narrower nasal cavities than those from hot, humid climates, such as Papua New Guinea or Gabon. The German team took computer-aided measurements of the nasal cavities of 100 skulls representing 10 human groups living in five different climates. They found that the nasal cavities of cold, dry climate populations are relatively high and show a larger and more abrupt change in diameter in the upper part of the cavity than those of hot, humid climate populations. This narrowing of the nasal passage enhances contact between the air and the mucosal tissue, which helps to warm and humidify that air. Cold, dry climate populations also show a relatively longer nasal cavity, giving this population more space in which to bring incoming air in line with body temperature. Microscopic hairs called cilia, which line the nasal passage, help to keep out pathogens and dust that may infect or irritate the lungs, and the cilia work more efficiently when incoming air is moist. Proper heating and humidification of air in colder climates is important for respiratory health. In warm-climate-adapted populations, inhalations are not directed toward the narrow upper part of the nasal cavity for warming. So people from warm climates, moving into cold climates, could be more susceptible to colds and related diseases.