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Lecture 3

ANTC41H3 Lecture Notes - Lecture 3: Frostbite, Mania, Vasoconstriction

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Mike Callaghan

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ANTC41 Lecture 3 Cold Weather and the Inuit
Key question: how have the Inuit adapted to life in arctic environments?
3.1 Today
Cold weather environments (what the artic environment presents)
Human physiological responses to cold
The Inuit (Specifically the Canadian Inuit)
Problems and discussion
3.2 Cold environments
A brief history of the arctic
During the mid to late Pleistocene is when the artic begins to emerge, as its own ecosystem. Most of the flora
and fauna (plants and animals) that we find in the artic today came there from the Rocky Mountains and from
the highlands of Asia. Historically there were huge swings in the climate. Between the ice ages there are warm
periods (during these warm periods biotic life changes dramatically).
In terms of people in the artic, genetically (through the testing of mitochondrial DNA) suggests that early artic
populations may have arrived there around five thousand years ago. They arrived there in a different migration
from native North Americans and South Americans and from the current Inuit. They are known as the pre-
Inuit people, they arrived and were supplanted (possibly from a migration via a land bridge from Russia). This
population began to populate all of North and South America and became the American Aboriginals that we
know today. A later wave of migration seems to be today’s Inuit.
Stresses that the Artic environment produces: (energy problem)
Prolonged low temperatures
Low biological productivity (it’s hard to grow things)
Light/dark seasonal cycles (affects our mental health as well as our physical health)
Low energy, low variety (only very few things can grow), the artic ecosystem is very fragile
Rich water (in terms of organic matter)! (Sometimes) rich soil!
3.3 human responses to cold
Soldiers fighting in the Korean War (early 1950s), an anthropologist studied the data of cold injuries during the
war (frostbite). Black soldier were four times more likely to suffer from cold weather injuries than white
soldiers during the Korean War. This suggests that there is something biological going on. From an
anthropological point of view, during this time there was still segregations or inequality between individuals of
different skin colour. Could this factor influence the quality of equipment that was handed to the black man?
There is obviously a biological factor but there may also be political and cultural factors as well. How would
you go about getting data to support the claims? You can’t necessarily relay on what the black war veterans
say because they most likely don’t want to speak ill of their comrades.
3.4 hair colour
The anthropologist went Norway; they had good data about their soldiers. Norway during the Second World
War had a standing army. They repeated the study and looked for incidences of cold weather injuries in
Norwegian soldiers during world war two. They found that brown haired soldiers were more likely to get cold
injuries than blond hair soldiers. This kind of goes against the argument that theres a political factor that
relates to cold injuries. There seems to be a hereditary aspect to how we respond to the cold.
3.8 bodies in the cold
Humans are endotherms, which means that our heat comes from inside, we create our own energy from the
inside which means that we have to heat ourselves up. We do relay on the sun but we also have an internal
thermoregulatory system.
Our thermoregulatory system is pretty sophisticated
If our core temperature gets to 33 degrees then the system fails and when our core temperature becomes 25
degrees it results in death.
It’s an energy problem, the human body needs energy to work. The cold makes the transfer of energy difficult (it
slows it down)
There are ways to prevent the shutting down of the body due to cold temperatures

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Vasoconstriction: the constriction/narrowing of the blood vessels it reduces the amount of heat you will
lose through the surface of the skin. The constricted blood vessels allow the warm blood to circulate
closer to the core of the body (where warmth and nutrients/oxygen are vital)
Shivering: it’s a temporary method and it could raise your production of heat (three times above
normal), you can’t really work efficiently when you’re shivering (interruption). Note that babies can’t
Rising base metabolic rate (rate is unit over time): We all have a resting metabolic rate (average for
women is 2000 calories/day, for men it is around 2500 calories/day). One of the ways that the body
responds to the cold is by turning up the ‘furnace’: burning more calories. The metabolism of food is
thermogenetic, in other words it produces heat. This process is known as nonshivering thermogenesis
(Latin translation = creating heat). It is beneficial for many reasons; one of these reasons is that it warms
you from the core (more efficient, heats from the core and then circulates it outwards). As an adult you
can increase your base metabolic rate in the cold by 25% while babies can increase it by 170%. Inuit
people are able to raise their base metabolic rate much higher than the average population (most likely
an adaptive trait).
Brown fat is a type of adipose tissue (fat cells). Fat is super storage of energy and brown fat is extra
special fat (it looks different, darker in colour). Brown fat has the ability to generate heat (it is
thermogenetic). Babies have a lot of brown fat on their bodies (especially on the torso). As we age we
lose our brown fat, however some populations (especially those in the artic) can retain brown fat (brown
fat persistence) 3.5 Bergmann’s rule
3.6 Allens rule
Allen was an American zoologist, who came up with his rule in 1877. It is similar to Bergmann’s rule but it is
slightly different. He looked at the relationship between surface area and mass. In endothermic species the
appendages of those in cold climate tend to be shorter than in animals of the same species in warmer climates.
The appendages get smaller the colder the climate gets… this is a characteristic that allows for the retention of
heat. At cold climates we should expect populations with short appendages, greater mass, with low surface area
(decrease the amount of heat that is radiated).
German Biologist, Bergmann, came up with this
rule in 1847. The graph shows a map of Sweden.
The y-axis shows latitude starting at 57N (which
is fairly north) and goes up to 66N (Artic). The x-
axis shows the average body mass of moose. The
further north the moose are located the bigger the
moose are. Bergmann’s rule generally applies to
mammals and it states that for a given species or a
given population organisms of greater mass are
found at higher latitudes or in colder
environments. In other words, the further north
you go the bigger you get. Note that it is NOT
larger but more massive (which is explained by
Allens rule). Bergmanns rule works even in the
archeological evidence.
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