Chapter 2: A Spoonful of Sugar Makes the Temperature Go Down

Insulin dependent diabetes is one of the most common chronic diseases in the world today. This is a hereditary disease that is caused by the inability of Beta cells in the pancreas to produce insulin. This is problematic because insulin is responsible for breaking down glucose present in the blood for energy and therefore keeps blood glucose levels from getting too high. While diabetes is considered a heritable disease, it is believed that genetics give you a predisposition for developing diabetes and then it is some environmental cue that actually prompts the onset. When trying to determine what evolutionary advantage could come from having diabetes, Dr. Moalem noticed there are some populations in which the incidence rate is very high and other populations where diabetes is virtually nonexistent. Insulin dependent diabetes is most common at high latitudes, predominantly in Finland, Sweden, the UK, and Norway, whereas in populations at low latitudes, like the people of African and Hispanic descent, diabetes is quite rare. Upon much research, Dr. Moalem came to the conclusion that insulin dependent diabetes must promote survival in extremely cold temperatures. While this is a hotly debated hypothesis, there are many facts to back it up. Diabetes is characterized by excessive water loss and excessive increase in blood glucose levels. This may be beneficial in very cold climates because the decrease in water volumes means there is less water in the body that could potentially freeze and the large amount of sugar in the blood significantly lowers its freezing point. It is believed that whatever gene is responsible for diabetes was selected for during the Younger Dryas, the most recent Ice Age. In support of this theory, children are most often diagnosed with diabetes in the colder months when the temperature begins to drop.