Humans have at least one genetic disease – In the future could we have hundreds?
What is the point of having a blog if you are not going to engage in off-the-cuff speculation. So here goes-
Every one of our genes is under constant threat of mutation from radiation, free radicals and merely being mis-copied during replication (just to name a few). So it stands to reason that genes that encode attributes that don’t improve your chance of survival (or reproduction) will, given enough time, mutate to create a different attribute or eventually mutate completely out of existence! This loss of useless genes through mutation will be the focus of this theoretical warm wax and polish of a blog post.
So sometime in our evolutionary history we (what ever we were) could synthesize our own vitamin C (1). Many animals can still do it, like mice, elephants and lemurs, but we (like our fellow great apes) lost the ability around 60 million years ago (1). Vitamin C production in vertebrates requires three enzymes and only one of these enzymes has mutated out of existence in humans (we still have the other two) (1). So why did this happen? Well- we were eating enough vitamin C in our diet, so when the inevitable happened and one of our genes mutated, it did not affect our survival. Vitamin C production in animals that eat enough vitamin C is what’s called a “neutral trait”. Which basically means in the eyes of evolution it’s a bit of a “meh…..stay, go, I don’t care”.
So here’s where I’ll get a bit theoretical – if vitamin C production can become redundant because of diet, what could become redundant (in the eyes of evolution) because of modern medicine? Take diabetes as an example- type 1 diabetes used to be a death sentence, then a Polish doctor discovered that if you take out a dog’s pancreas, the dog’s urine becomes so sweet that flies flock to it as if it were some form of canine honey. This became the first animal model of type 1 diabetes. 30 years later Frederick Banting- a Canadian doctor- began the first treatment of a diabetic patient with animal pancreatic extract -aka- insulin (the first patient died from the impurities in the insulin, but they got better at it – see the side note). Now, thanks to genetically engineered yeast and bacteria producing insulin, type 1 diabetes barely affects life expectancy – perhaps reducing it by as little as 4 years in developed countries (2). Incredibly, new technology is being trialed where artificial pancreas are implanted into patients from a very young age. These machines will tightly regulate blood sugar levels, perhaps further improving the life expectancy of diabetic patients (3).
So here’s the big question – could insulin production become a “neutral trait” in the eyes of evolution? Could we start treating diabetes so well that it poses no survival pressure? Theoretically, the genes involved in insulin production would eventually (millions of years maybe) mutate out of existence in everyone. And why stop with diabetes? What about other diseases that in the future might be treated with apparatuses which administer a compound to replace a spontaneously occurring deficiency. such as dopamine production in Parkinson’s sufferers or the production of Factor VIII in hemophiliacs. Will these diseases also become evolutionarily neutral and therefore eventually have a prevalence of 100%? After all, in the eyes of the Mouse, not being able to produce vitamin C would be considered a genetic disease, which 100% of all humans have.
Basically I’m saying all our organs will eventually be replaced by machines which we will monitor with our iPhone 7939.
Side note – diabetes was such an awful affliction, there used to be whole wards filled with comatose children on their literal deathbed. Once Frederick Banting had figured out the purification process of insulin, he began treating these children with fantastic results. One account describes Banting and his colleagues treating children in a ward filled with 50 comatose patients and their despairing parents. Going from bed to bed, they treated the entire ward with their purified insulin. By the time they reached the last terminal child, the first children were recovering from their coma to the relief and jubilation of their families.
Drouin, Guy, Jean-Rémi Godin, and Benoît Pagé. “The Genetics of Vitamin C Loss in Vertebrates.” Current Genomics 12.5 (2011): 371–378. PMC.
Miller, Rachel G. et al. “Improvements in the Life Expectancy of Type 1 Diabetes: The Pittsburgh Epidemiology of Diabetes Complications Study Cohort.” Diabetes 61.11 (2012): 2987–2992. PMC.
Dassau, Eyal et al. “Clinical Evaluation of a Personalized Artificial Pancreas.”Diabetes Care 36.4 (2013): 801–809. PMC.