304 CHAPTER 13 | Human Adaptation to a Changing WorldThe process of growth and development begins with re-
production, and high altitude exerts considerable effects on
this process. For populations who have not adapted to high
altitude, successful reproduction is not possible without some
cultural interventions. For example, take the case of fertility
among Spanish colonialists in the city of Potosi high in the
Andes founded in order to mine the “mountain of silver” that
towers above the community. For the first fifty-four years of
this city’s existence no Spanish child was born who survived
childhood. Indigenous populations did not have these prob-
lems. To ensure reproductive success, Spanish women began
the cultural practice of retreating to lower altitude for their
pregnancies and the first year of their children’s lives.^5
At high altitudes cold stress is also a problem. As de-
scribed in the previous chapter, a stocky body and short
limbs help individuals conserve heat while the opposite
facilitates heat loss. These phenomena have been formal-
ized into two rules named after the naturalists who made
such observations in mammals. Bergmann’s rule refers
to the tendency for the bodies of mammals living in cold
climates to be more massive than members of the same
species living in warm climates (Figure 13.3). Allen’s rule
refers to the tendency of mammals living in cold climates
to have shorter appendages (arms and legs) than members
of the same species living in warm climates (Figure 13.4).Adaptation to Cold
Cold stress can exist without high altitude, as it does in the
Arctic. In addition to the previously mentioned patterns
of body and limb shape and size, other cold responses are
also evident in Arctic populations.order to carry more oxygen. Because of differences in ge-
netic makeup, individuals’ physiological responses begin
at varying altitudes.
Developmental adaptations are seen in individuals
who spend their childhood period of growth and develop-
ment at high altitude. Among the highland Quechua, for
example, both the chest cavity and the right ventricle of
the heart (which pushes blood to the lungs) are enlarged
compared to lowland Quechua. This may have genetic
underpinnings in that all Quechua experience a long
period of growth and development compared to the aver-
age person in the United States.Observing that Kenyan runners, like Rita Jeptoo pictured here, have
won most of the major marathon competitions over the past several de-
cades, coaches have emulated the Kenyan approach. Adaptation to the
hot, dry yet mountainous region leads to a long lean build (a product of
the heat adaptation) and increased oxygen-carrying capacity. Although
runners worldwide tend to be tall and lean, many athletes now train at
high altitude so that when race day comes, their red blood cell count
and hemoglobin levels allow them to carry more oxygen.© Reuters/Mike Segar/Landov22
2444Surface area 24
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Volume 8
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volumeBergmann’s RuleFigure 13.3 Bergmann’s rule refers to the observation
that as overall body size increases, the amount of surface
area increases less rapidly than the amount of volume. This
accounts for the tendency for mammals living in cold climates
to be more massive than members of the same species living
in warmer climates. This allows for the conservation of heat in
cold climates and its dissipation in warm climates.(^5) Wiley, A. S. (2004). An ecology of high-altitude infancy: A biocultural
perspective. Cambridge, England: Cambridge University Press.
Bergmann’s rule The tendency for the bodies of mammals
living in cold climates to be shorter and rounder than members
of the same species living in warm climates.
Allen’s rule The tendency for the bodies of mammals living
in cold climates to have shorter appendages (arms and legs)
than members of the same species living in warm climates.
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