Men may have larger noses than women because they generally have more muscle, demanding larger noses to breathe in more oxygen, researchers say.
Modern humans have smaller noses than ancient humans, including Neanderthals, the closest extinct relatives of modern humans. Scientists have suggested human nose size is linked to how much oxygen a person's body needs — the skeletons of ancient humans suggest they had larger body masses than modern humans, and so may have needed larger noses to help supply them with the greater levels of oxygen those bodies would have needed. However, because fossil skeletons of ancient humans are often fragmented and incomplete, researchers could not confirm whether nose size was linked with body mass. [Men vs. Women: 6 Key Physical Differences Explained]
Past research of a wide range of modern humans globally also revealed that men generally have larger noses than women, and typically have larger nasal cavities and airways behind the nose as well. In addition, men consume more oxygen during nasal breathing than women. Still, this did not confirm that differences in nose size are due to how much oxygen people need — perhaps nose size was linked to some other function, or no function at all.
To help answer these questions about nose size, researchers analyzed when nose size begins to change in the sexes. They focused on 18 female and 20 male volunteers, all of European descent, relying on nearly 300 data points from X-rays and other physical exams gathered from them from ages 3 to more than 20 years from the Iowa Facial Growth Study.
The researchers found that males and females had similar nose sizes when they were young. However, male noses usually start growing larger than female noses during adolescence, coinciding with how males generally consume more oxygen and energy than females upon puberty. All in all, the male noses they examined were about 10 percent larger than female noses on average.
"As body size increases in males and females during growth, males exhibit a disproportionate increase in nasal size," said study lead author Nathan Holton, a biological anthropologist at the University of Iowa. "This follows the same pattern as energetic variables such as oxygen consumption."
Males typically gain more lean muscle during adolescence than females, which demands more energy and oxygen. The finding that male noses may get larger during adolescence as well suggests nose size is linked with oxygen consumption. The scientists detailed their findings online Oct. 31 in the American Journal of Physical Anthropology.
These findings might also yield insights on human evolution.
"The large noses in groups like Neanderthals may be constrained to be large because they had greater mass and therefore required more oxygen," Holton told LiveScience. "With the reduction in body mass seen in modern humans, these constraints would be lifted and noses would reduce in size."
The researchers acknowledge their research looked at fewer than 40 people, all of European descent, which might raise questions about whether or not these findings apply generally to all men and women. Still, the fact that past findings suggest men generally have larger noses than women globally suggests this research could hold true of people overall.