Human Adaptation to Climate: Temperature, Ultraviolet Radiation, and Altitude

Absolute humidity and the human nose: A reanalysis of climate zones and their influence on nasal form and function

“…Although the degree to which climate influences the nasal index has been debated (Hoyme, ; Hoyme and Işcan, ; Wolpoff, ), it is widely viewed that, as a basic measurement of nasal aperture shape, the nasal index broadly reflects climate‐mediated adaptations for modulating nasal airflow during respiration (Beall et al, ; Churchill et al, ; Evteev et al, ; Franciscus & Long, ; Lieberman, ; Noback et al, ). The findings of Weiner (), who demonstrated statistically significant relationships between living nasal index and average annual relative humidity ( R = 0.42), temperature ( R = 0.63), and especially absolute humidity ( R = 0.82), are commonly cited in support of this view.…”

“…Thomson and Buxton () also provide mean living nasal index (nasal breadth/nasal height ×100) values for each of their 147 populations, providing the opportunity to investigate the potential influences of temperature and absolute humidity on an aspect of human nasal morphology widely argued to evince climatic adaptation (Beall et al, ; Churchill et al, ; Evteev et al, ; Franciscus & Long, ; Lieberman, ; Noback et al, ; Yokley, ). While Thomson and Buxton's 147 living populations encompass most of the human geographic distribution, this sample lacks representatives from one of the most extreme climates inhabited by humans: the Arctic Circle.…”

“…Fortunately, if the temperature and absolute humidity for a given locale can be determined, the amount of modification required to maintain homeostatic respiratory function can easily be calculated by subtracting the temperature and moisture content of inspired air from those of the isothermic saturation boundary (37° C, 44 g/m 3 ) (Williams, ). Moreover, given the vast range of climates that humans inhabit, the amount of modification required can vary drastically (Beall, Jablonski, & Steegmann, ; Lieberman, ; Walker et al, ). For example, air inspired in a tropical environment with a temperature of 35°C and absolute humidity of 35.6 g/m 3 requires considerably less modification (+2°C, +8.4 g/m 3 ) than air inspired in an Arctic environment with a temperature of −25°C and absolute humidity of 0.63 g/m 3 (+62°C, +43.37 g/m 3 ).…”

Ecogeographic variation across morphofunctional units of the human nose

“…Similarly, projection of the external pyramid ( Figure 1) has also elicited considerable attention (Carey & Steegmann, 1981;Cottle, 1955;Franciscus, 1995;Franciscus & Trinkaus, 1988;Negus, 1958;Woo & Morant, 1934), with Carey and Steegmann (1981) notably finding a strong inverse relationship (r 5 20.72) between nasal projection and the mean absolute humidity of the coldest month of the year. In light of such findings, it has become generally accepted that external portions of the nasal complex evince climatic adaptation, with leptorrhine (relatively tall and narrow) nasal apertures and projecting nasal bones commonly cited as evolutionary adaptions for breathing in cold-dry environments (see Beall, Jablonski, & Steegmann, 2012). However, as noted by Franciscus and Long (1991), such assertions have historically relied on the "correlational method," in which associations between nasal morphology and climatic variables are taken as evincing adaptation-despite the lack of an explicit functional mechanism through which particular morphologies might confer fitness during natural selection.…”

Migration-Selection Balance Drives Genetic Differentiation in Genes Associated with High-Altitude Function in the Speckled Teal (Anas flavirostris) in the Andes

“…2017a), including genes involved in the HIF pathway, as well as mitochondrial elements (Scheinfeldt and Tishkoff 2010; Storz et al. 2010; Beall et al. 2012).…”