Prompt 1: Big Idea 1 and 4: Link of the genetic
predisposition of Type 1 and Type 2 diabetes to a response to a cold
environment
Dr. Moalem makes a compelling argument in Chapter 2 of Survival of the Sickest linking the
genetic pre-disposition of diabetes to a defense against a cold environment,
such as the rapid drop in temperature during the Younger Dryas (p. 33-34;
44-46). This seems particularly
appropriate for Type 1 diabetes and it’s higher rate among Northern Europeans
(p. 26); the intense cold of sudden climate change in that geography being the
natural selection driver to a diabetes genetic link (Big Idea 1).
This link to a cold defense seems far less clear for a
genetic predisposition for Type 2 diabetes, although Moalem points out the
stronger apparent link of Type 2 to genetics (p. 26). For Type 2 diabetes, lifestyle (specifically obesity) seems
to be the major driver. Moalem
also points out an example of the Pima Indians’ high rate of diabetes where
their traditional “hunter-gatherer” lifestyle may have produced metabolisms
that cannot handle carbohydrate-heavy modern diets; it is difficult to see
where a response to cold weather played a major role. Another counter example would the extremely high rate of
Type 2 diabetes manifesting itself in India, which had been specifically
attributed to a rise in economic conditions and a “modern” diet (ref: Modern Ways Open India’s Doors to Diabetes,
NY
Times, September 13, 2006). For
India, there is even less of a link to a cold climate and even a
“hunter-gatherer” rationale is less persuasive given India’s place as one of
the four cradles of civilization.
Particularly for Type 2 diabetes, as Moalem states, the cause “is a
complex combination that can involve inheritance, infections, diet and
environmental factors” (p. 25; Big Idea 4).
Questions: What is the evidence linking Type 2 diabetes
genetics to a cold climate defense?
Given the strong possibility that we are entering a period of global
warming, what are the implications on Type 1 diabetes genetics? If long-term global warming is real,
does modern medicine’s ability to treat diabetes (especially Type 1) in effect
thwart natural selection? If this
works against natural selection, is this good/bad for the human species, and
what are the ethical implications?
(Rachel Chang, rchang4@students.d125.org)
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ReplyDeleteType 2 diabetes genetics is linked to a cold climate defense.This is because type 2 diabetes cannot react to insulin. Type 1 diabetes is when the body does not produce insulin and Type 2 diabetes is when the body doesn't react to insulin. (http://www.medicalnewstoday.com/articles/7504.php) Type 1 diabetes is not because of lifestyle and is obtained by losing the beta cells that are in the pancreas that produce insulin. This causes the blood sugar levels to be able to rise to dangerous levels (http://www.scientificamerican.com/article.cfm?id=a-diabetes-cliffhanger). This insulin helps the body by breaking down glucose and allowing sugar to be used by cells. As read in Moalem in defenses against cold, we pee when freezing to increase sugar to blood ratio which prevents freezing(39-40). Like this, type 2 diabetes allows excess sugar to be around in the blood which prevents freezing and is a selective advantage in cold weather. Also, since type 2 diabetes is also obtainable without genetics, when we live in cold environments we may get this disease as it helps survive in harsh, cold environments.
ReplyDeleteThe implications that can be made by global warming is that type 1 diabetes will decrease because type 1 diabetes also causes a large amount of glucose in your blood. When the world gets warmer and warmer, type 1 diabetes will be a selective disadvantage and people with type 1 diabetes will decrease due to natural selection.(Big Idea 1).