Biology Reference
In-Depth Information
Adams found a statistically significant relationship between body shape and trophic mor-
phology, taking phylogeny into account.
Human Nasal Cavity Morphology and the Climatic Environment: Temperature and
Vapor Pressure
The functional morphology of the nasal cavity morphology was investigated by Noback
and colleagues (2011). The nasal cavity functions to humidify and warm the air before it
reaches the lungs, and the question posed by this study is whether humans that live in
more demanding environments (with lower temperatures and higher aridity) have nasal
cavities that enhance turbulence and air
wall contacts to improve the conditioning of the
air. Noback and colleagues recorded three-dimensional coordinates of 21 landmarks on
the bony morphology of the nasal cavity of 100 individuals, from five climatic zones
(selecting specimens to represent indigenous populations of the area rather than those
affected by modern western lifestyles or health care). They examined the relationship
between nasal cavity shape and indicators of temperature and aridity, which include
monthly observations of temperature and vapor pressure (obtained from KNMI Climate
Explorer) from 1901 to 2006 for the geographical locations (or region) of each individual
cranium. The data on climate may not represent the climatic conditions over the past thou-
sands of years during which the populations diversified but it is the most comprehensive
and detailed database on climate available. The climate variables include (1) mean yearly
temperature, (2) coldest monthly temperature, (3) warmest monthly temperature, (4) mean
yearly vapor pressure, (5) lowest monthly vapor pressure and (6) highest monthly vapor
pressure. The shape data comprise the means for each of the 10 populations.
SA1 of the environmental block is a general climatic factor, with all climatic variables
loading positively and nearly equally on that axis, with the two extremes being the coldest
and driest versus warmest and most humid. SA2 for the environmental block is a contrast
between temperature and vapor pressure (i.e. warm and dry versus cool and humid). SA1
explains 94.3% of the covariation between nasal cavity shape and climate, yielding a corre-
lation of 0.77 between the scores on the paired SA1. SA2 explains only 5.1% of the covaria-
tion between shape and climate, yielding a correlation of 0.55 between the two blocks.
Although the covariances explained by both SA1 and SA2 are statistically significant based
on permutation tests, only SA1 is interpreted because it explains vastly more of the covari-
ance between the blocks. The shape changes associated with climate are found in the nasal
aperture, upper nasal cavity and nasopharynx. Populations from cool dry climates differ
from those from warm humid climates by relatively higher and narrower nasal aperture, a
relatively high and narrow upper nasal cavity and a shortening of the nasopharynx with
an increase in the relative length of the posterior cavum length. The authors conclude that
the morphology of the bony nasal cavity appears to be associated mainly with temperature
and the nasopharynx with humidity, with the changes in shape being consistent with
increased contact between air and mucosal tissue in cold, dry climates (increasing turbu-
lence during inspiration and increasing the surface area to volume ratio in the upper nasal
cavity). They also recognize that the shape differences are modest and that populations
overlap, perhaps suggesting that the shape of the nasal cavity represents a compromise
and/or that nasal cavity morphology lacks extreme specializations that would reduce the
versatility of a generalist, mobile species.
