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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts |News Archive Nov 22, 2013

 

Male noses grow disproportionately larger than female noses beginning at puberty,
a University of Iowa study has found. The reason: Males need to breathe
in more oxygen to feed muscle mass than females.

Image courtesy of the College of Dentistry.







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The big male nose

Human noses come in all shapes and sizes. But one feature seems to hold true: Men’s noses are bigger than women’s.

A new study from the University of Iowa concludes that men’s noses are about 10 percent larger than female noses, on average, in populations of European descent.


The size difference, the researchers believe, comes from the sexes’ different builds and energy demands: Males in general have more lean muscle mass, which requires more oxygen for muscle tissue growth and maintenance.

Larger noses mean more oxygen can be breathed in and transported in the blood to supply the muscle.


The researchers also note that males and females begin to show differences in nose size at around age 11, generally, when puberty starts. Physiologically speaking, males begin to grow more lean muscle mass from that time, while females grow more fat mass. Prior research has shown that, during puberty, approximately 95 percent of body weight gain in males comes from fat-free mass, compared to 85 percent in females.


“This relationship has been discussed in the literature, but this is the first study to examine how the size of the nose relates to body size in males and females in a longitudinal study,”

“We have shown that as body size increases in males and females during growth, males exhibit a disproportionate increase in nasal size. This follows the same pattern as energetic variables such as oxygenate consumption, basal metabolic rate and daily energy requirements during growth.”

Nathan Holton, assistant professor, UI College of Dentistry and lead author of the paper, published in the American Journal of Physical Anthropology.


It also explains why our noses are smaller than those of our ancestors, such as the Neanderthals. The reason, the researchers believe, is because our distant lineages had more muscle mass, and so needed larger noses to maintain that muscle. Modern humans have less lean muscle mass, meaning we can get away with smaller noses.

“So, in humans, the nose can become small, because our bodies have smaller oxygen requirements than we see in archaic humans,” Holton says, noting also that the rib cages and lungs are smaller in modern humans, reinforcing the idea that we don’t need as much oxygen to feed our frames as our ancestors. “This all tells us physiologically how modern humans have changed from their ancestors.”

Holton and his team tracked nose size and growth of 38 individuals of European descent enrolled in the Iowa Facial Growth Study from three years of age until the mid-twenties, taking external and internal measurements at regular intervals for each individual.


The researchers found that boys and girls have the same nose size, generally speaking, from birth until puberty percolated, around age 11. From that point onward, the size difference grew more pronounced, the measurements showed.


“Even if the body size is the same,” Holton says, “males have larger noses, because more of the body is made up of that expensive tissue. And, it’s at puberty that these differences really take off.”
Holton says the findings should hold true for other populations, as differences in male and female physiology cut across cultures and races, although further studies would need to confirm that.

Prior research appears to support Holton’s findings. In a 1999 study published in the European Journal of Nutrition, researchers documented that males' energy needs doubles that of females post-puberty, “indicating a disproportional increase in energy expenditure in males during this developmental period,” Holton and his colleagues write.

Another interesting aspect of the research is what it all means for how we think of the nose. It’s not just a centrally located adornment on our face; it’s more a valuable extension of our lungs.

“So, in that sense, we can think of it as being independent of the skull, and more closely tied with non-cranial aspects of anatomy,” Holton says.

Abstract
Researchers have hypothesized that nasal morphology, both in archaic Homo and in recent humans, is influenced by body mass and associated oxygen consumption demands required for tissue maintenance. Similarly, recent studies of the adult human nasal region have documented key differences in nasal form between males and females that are potentially linked to sexual dimorphism in body size, composition, and energetics. To better understand this potential developmental and functional dynamic, we first assessed sexual dimorphism in the nasal cavity in recent humans to determine when during ontogeny male-female differences in nasal cavity size appear. Next, we assessed whether there are significant differences in nasal/body size scaling relationships in males and females during ontogeny. Using a mixed longitudinal sample we collected cephalometric and anthropometric measurements from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations. We found that males and females exhibit similar nasal size values early in ontogeny and that sexual dimorphism in nasal size appears during adolescence. Moreover, when scaled to body size, males exhibit greater positive allometry in nasal size compared to females. This differs from patterns of sexual dimorphism in overall facial size, which are already present in our earliest age groups. Sexually dimorphic differences in nasal development and scaling mirror patterns of ontogenetic variation in variables associated with oxygen consumption and tissue maintenance. This underscores the importance of considering broader systemic factors in craniofacial development and may have important implications for the study of patters craniofacial evolution in the genus Homo. 2013. © 2013 Wiley Periodicals, Inc.


Thomas Southard, professor and chair of orthodontics in the UI College of Dentistry, is a contributing author on the paper. Other authors are Todd Yokley, from Metropolitan State University in Denver, and Andrew Froehle, from Wright State University, in Dayton, Ohio.

The Department of Orthodontics in the UI College of Dentistry funded the research.