28
2 The Genetic Context
protections against hypothermia. Houghton [1] supports Damon’s conclusion that
“Climate. . .does indeed seem to be the major regulatory factor for human body size
and proportion” and he notes that this statement subsumes the classical biological
rules of Bergmann (1848) and Allen (1877):
Bergmann’s rule says that, for closely related mammals or birds, those living in cold regions
tend to have greater body mass than those living in warm regions. Allen’s rule says that
animals living in cold climates tend to have shorter extremities than those living in hot
climates. . . In human terms, larger and more muscular people should be found in cold climates, where large muscle mass can produce more body heat, and the relatively smaller
surface area of a larger body lessens heat loss. Smaller-bodied, or at least more linear, people should be found in hotter climates, where endogenous heat production is less necessary,
and a relatively larger surface area allows for more efficient cooling. The geometric basis
is that the volume and mass increase as the cube of the linear dimensions, whereas surface
area only increases as the square of the linear dimensions (p. 167).
Statistics based on factors such as stature/weight index and sitting to standing
height index (ratio × 100), which are measures of a cold-adapted body type, suggest
that New Zealand Maori are more cold-adapted than any other recorded cold climate
group. Eskimos and Lapps have sitting to standing height indices of about 52.5,
Maori has one of 53.8 [28]. The stature/weight index “ranges from under 2.6 for
males from cold climate regions such as Finland, Iceland and England, through to
values above 3.2 for Vietnam, Burma and India (Molnar, 1983). The Polynesian
male values of between 2.22 and 2.39. . .are lower than that recorded from any coldclimate group” [29].
Houghton concludes that the extreme cold adaptation of the Polynesian body type
relates to an oceanic environment that poses very significant risks of hypothermia:
“The oceanic environment is potentially and very frequently very cold, whether for
voyaging, for the more mundane but routine activities of reef and coastal fishing
in a small-island existence, or at times even for life ashore” [30]. With respect to
canoe voyaging, Houghton quotes heat loss and heat gain figures which illustrate
the advantage of muscle mass in cold responses and demonstrates the advantage
of the Polynesian phenotype over that of a non-cold-adapted individual in wet/cold
oceanic conditions conducive to hypothermia:
These heat loss and heat gain figures show that in wet/cold conditions at sea – relatively
inactive, shivering and exposed – the smaller body is able to produce only 42–43% of body
heat lost, with an hourly deficit of 1800–1950 kJ. The larger body is better off but, for any
individual, such exposure is unsustainable for more than an hour or so. For example, Pugh
(1967) noted a drop of core temperature from 39.5 ◦ C to 36.4 ◦ C in 25 minutes in an inactive
subject in wet-cold conditions of 5 ◦ C and 14 kph wind.
If shelter is largely obtained from the wind – say to about 4 kph – the heat loss is
reduced to about half the exposed loss (Pugh 1966, Clark and Edholm 1985). Thus, with a
heat production of about 1750 kJ/hour, the large body can just maintain heat balance. The
small body remains in deficit of about 300 kJ/hour. . .With such a deficit a core temperature
of about 32 ◦ C, a condition of moderate hypothermia, is reached within eight hours. . .If the
maximum heat output from shivering has already been reached, such increase would have
to arise from deliberate muscular activity (p. 174).
2 The Genetic Context
protections against hypothermia. Houghton [1] supports Damon’s conclusion that
“Climate. . .does indeed seem to be the major regulatory factor for human body size
and proportion” and he notes that this statement subsumes the classical biological
rules of Bergmann (1848) and Allen (1877):
Bergmann’s rule says that, for closely related mammals or birds, those living in cold regions
tend to have greater body mass than those living in warm regions. Allen’s rule says that
animals living in cold climates tend to have shorter extremities than those living in hot
climates. . . In human terms, larger and more muscular people should be found in cold climates, where large muscle mass can produce more body heat, and the relatively smaller
surface area of a larger body lessens heat loss. Smaller-bodied, or at least more linear, people should be found in hotter climates, where endogenous heat production is less necessary,
and a relatively larger surface area allows for more efficient cooling. The geometric basis
is that the volume and mass increase as the cube of the linear dimensions, whereas surface
area only increases as the square of the linear dimensions (p. 167).
Statistics based on factors such as stature/weight index and sitting to standing
height index (ratio × 100), which are measures of a cold-adapted body type, suggest
that New Zealand Maori are more cold-adapted than any other recorded cold climate
group. Eskimos and Lapps have sitting to standing height indices of about 52.5,
Maori has one of 53.8 [28]. The stature/weight index “ranges from under 2.6 for
males from cold climate regions such as Finland, Iceland and England, through to
values above 3.2 for Vietnam, Burma and India (Molnar, 1983). The Polynesian
male values of between 2.22 and 2.39. . .are lower than that recorded from any coldclimate group” [29].
Houghton concludes that the extreme cold adaptation of the Polynesian body type
relates to an oceanic environment that poses very significant risks of hypothermia:
“The oceanic environment is potentially and very frequently very cold, whether for
voyaging, for the more mundane but routine activities of reef and coastal fishing
in a small-island existence, or at times even for life ashore” [30]. With respect to
canoe voyaging, Houghton quotes heat loss and heat gain figures which illustrate
the advantage of muscle mass in cold responses and demonstrates the advantage
of the Polynesian phenotype over that of a non-cold-adapted individual in wet/cold
oceanic conditions conducive to hypothermia:
These heat loss and heat gain figures show that in wet/cold conditions at sea – relatively
inactive, shivering and exposed – the smaller body is able to produce only 42–43% of body
heat lost, with an hourly deficit of 1800–1950 kJ. The larger body is better off but, for any
individual, such exposure is unsustainable for more than an hour or so. For example, Pugh
(1967) noted a drop of core temperature from 39.5 ◦ C to 36.4 ◦ C in 25 minutes in an inactive
subject in wet-cold conditions of 5 ◦ C and 14 kph wind.
If shelter is largely obtained from the wind – say to about 4 kph – the heat loss is
reduced to about half the exposed loss (Pugh 1966, Clark and Edholm 1985). Thus, with a
heat production of about 1750 kJ/hour, the large body can just maintain heat balance. The
small body remains in deficit of about 300 kJ/hour. . .With such a deficit a core temperature
of about 32 ◦ C, a condition of moderate hypothermia, is reached within eight hours. . .If the
maximum heat output from shivering has already been reached, such increase would have
to arise from deliberate muscular activity (p. 174).