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Survival of the Sickest by Dr. Sharon Moalem (with Jonathan Prince)

Updated: Feb 24, 2023

“Somewhere in your genetic code is the tale of every plague, every predator, every parasite, and every planetary upheaval your ancestors managed to survive. And every mutation, every change, that helped them better adapt to their circumstances is written there.” (16)

Dr. Sharon Moalem started his medical career at the young age of 15, after watching his grandfather suffer from Alzheimer’s and a unique disease named hemochromatosis. He was curious about why his grandfather felt a little better after giving away blood, and plowed through multiple medical articles searching for the answer. Hemochromatosis is also known as “iron overload,“ which is why after giving iron (in the form of blood), he felt more energized. After he was diagnosed Alzhiemer’s, Dr. Moalem had a gut feeling that the two were connected. Iron overload could definitely damage his brain. Since he was 15, no one believed him, but he was so determined to prove his point to the world, that he decided to delay medical school to join a PhD program focused on neurogenetics. As he soon found out, hemochromatosis is a hereditary disorder which is very intriguing, because common conditions that are only caused by inheritance should die out along the evolutionary line under most circumstances. Evolution likes traits that help us survive and reproduce — it doesn’t like traits that weaken us or threaten our health. So hereditary disorders don’t really make sense at first glance. Why would genes that make people sick still be in the gene pool after millions of years? Well, during the Plague, and other pandemics, iron rich populations were left healthy, and although hemochromatosis might kill you in 40 years, it’s the only thing that’s going to keep you alive tomorrow, and that’s why it was genetically selected, and passed down in our DNA.

Before we move on to the review itself, let’s go ahead and learn about another *somewhat* hereditary disease, diabetes. Diabetes is when people become insulin resistant, or they don’t make enough insulin, which leads to a situation where there is too much sugar in the blood stream. (Also, quick note: if you want to learn more about diabetes or hemochromatosis check out my “What awareness is this month for” and check out months July and November. Go ahead, and follow the links in those months to learn more or to donate.) Anyway, to understand why diabetes is still in the gene pool, you first need to understand some basic knowledge. Diabetes probably first originated as a survival tactic for our ancestors during the Ice Age. You see, humans have 4 responses to the cold, that you probably have experienced before. Think back to a time when you were cold: the first response was that you probably first started shivering. Your body is trying to generate heat by burning calories and sugar in your muscles. The second response to the cold is one that you have definitely felt the effect of. It’s when your fingers start feeling numb and very jello like. As soon as the body senses cold, it closes off the capillaries in your extremities: first your fingers and toes; and then farther up your arms and legs. Once that happens, the body doesn’t completely regulate blood flow down there; only periodically. It mainly focuses on keeping your internal organs such as your liver, kidney, and intestines warm. It’s a natural triage — lose the finger, spare the liver. (35) Another very useful response, that most people from warm weather populations don’t have. It’s called brown fat cells; sometimes found in newborns and some adults such as Norwegian fisherman or Inuit hunters, haha. Basically, when blood sugar is delivered to a brown fat cell it is converted to heat on the spot, unlike normal fat cells that store it for future energy. It can essentially create heat without moving your muscles, so some scientists like to call it “non shivering thermogenesis”. Finally, the last, and most intriguing response is “cold diuresis” or otherwise known as, the immense need to pee when exposed to the cold. It’s quite natural really; the less water there is in our bodies’, the less chance there is to damage our delicate membranes. So, that’s why at the first onset of freeze, our body decides to offload all that excess water. The sharp increase in sugar concentration that’s directly intertwined with diabetes (as well as brown fat cells when you think about it), goes hand in hand with the fact that sugar is a natural antifreeze. That means the more sugar content there is in a liquid, the colder it has to get to freeze. Essentially increased sugar concentration and less water is helping us survive. Our ancestors that survived during the ice age got diabetes for a very good reason, and Mother Nature decided to keep it in our gene pool forever (just in case).

Dr. Moalem goes over hemochromatosis and diabetes more in depth in his book, but he also goes over cholesterol, lactose intolerance, green beans + gas, and even how fungi and viruses use mental manipulation so they can evolve, survive, and reproduce. It’s a very captivating read that intrigued me from the first page, all the way to the last. It refocuses diseases from the “whats” to the “whys” which encouraged me to ask more and more questions that were answered later on in the book, almost like a very experienced teacher. Dr. Moalem goes into detail on two subjects, evolution and medicine, and intertwined them in a way that could interest even the most book hating child, and even I devoured the book in just the first couple days of my summer break. I definitely recommend this book on your shelf, because it can capture anyone’s attention and gives a lot of necessary details.

“Fascinating, enlightening, and reader-friendly… this one not-to-be-missed fantastic journey across the evolutionary landscape of humankind.” - Rocky Mountain News


Moalem, Sharon, and Jonathan Prince. Survival of the Sickest: The Surprising Connections Between Disease and Longevity (P.S.). Reprint, Harper Perennial, 2008.

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