“Nothing in biology makes sense except in the light of evolution.”
– Theodosius Dobzhansky
Evolution is arguably one of the most widely supported and powerful theories in all of biology, and potentially science as a whole. It has been a dominant explanation for over 100 years. Once genetics entered the picture in the first part of the 20th century, Darwin’s common descent and Mendel’s inheritance were improved upon, greatly expanded, and solidified into the new synthesis of evolution. Consistently verified through genetics, paleontology, geology, ecology, microbiology, and many other fields of science, evolution has become a pervasively potent field of study. It has created huge disciplinary offshoots – including evolutionary biology, evolutionary genetics, and evolutionary anthropology to name a few – and has become the theoretical foundation for all of biology.
Some people today argue that humans are no longer under evolutionary pressures, and, thus, are no longer evolving. Though this seems to make sense superficially, it is simply not true. The first issue is that humans only live about 80 years; a mere snapshot of our species’ existence. It is difficult to observe phenotypic differences as a result of biological evolution in only a few decades. That being said, scientists have found some very recent biological changes have occurred, including the altered expression of the FTO gene. The FTO gene codes for a protein that regulates appetite. While it does not “make” a person obese (genes tend to predispose, not determine), it has been correlated with obesity. The catch? It seems to have only been expressed after about 1940, according to a study published just 2 days ago. The study (which can be found here) found that, after 1942, the FTO gene showed a strong correlation with increase BMI. Why, though, would a gene that has not changed suddenly become active?
What did change in the 1940’s? Technology. WWII offered an incredible economic boost to the US that massively increased technological enterprise and was the main contributing factor the world superpower status that the US achieved in the 40’s. As technology increased, labor decreased. After all, the main purpose of technology is to make human life simpler. When human life becomes simpler, people become more sedentary. New technology also allowed for cheaper, higher calorie, over-processed food. This one will take a while to work out. The difference could be epigenetic alteration, novel environmental stimuli, or even another gene interacting with FTO. While more testing will be needed to show exactly what happened in the early 40’s that altered FTO expression, the fact that something did occur, likely stemming from environmental changes, still remains. Biological evolution doesn’t have to be the changing of DNA sequence; that is far too simplistic. Anytime phenotypic or genotype ratios change on a species-wide level, evolution is occurring. No population is in Hardy-Weinberg equilibrium, and no population ever will be. Human wills continue to evolve biologically. While cultural evolution has exceedingly outpaced biological evolution, giving the mirage that biological evolution has “stopped,” the truth is that culture can either augment or stagnate biological evolution, depending upon the situation. A cultural change to drinking more milk may augment lactase persistence (and in fact, it did), while a cultural propensity to live in climate controlled housing year-round may slow other aspects of biological evolution. Nature doesn’t necessarily control natural selection; more broadly, the environment (cultural or natural) mediates evolution.
So, why is evolution important in medicine? Sure, doctors need to understand things like microbial evolution and how it plays a role in infectious diseases, but what about human evolution? How can a knowledge of human evolution impact medicine?
Cultural evolution has rapidly and drastically altered the human environment, thus changing how the human species evolves. More importantly, our environments have changed so aggressively that our bodies cannot keep up. (Before I go on, I have to make something clear. I am not a proponent of the Paleo Diet; if you’d like to know why, check out this post.) This means our bodies are often best adapted to the environments of the past (though these vary drastically). This has given rise to what are sometimes referred to as “mismatch diseases.” The list is extensive, but includes maladies such as atherosclerosis, heart disease, type-2 diabetes, osteoporosis, cavities, asthma, certain cancers, flat feet, depression, fatty liver syndrome, plantar fasciitis, and irritable bowel syndrome, to name a few. Some of these may not be actual mismatch diseases, but many of them likely are. Furthermore, many of these illnesses feed off one another, creating a terrible feedback loop. 100 years ago you’d likely die from an infectious disease; today, most people in developed nations will die from heart disease, type-2 diabetes, or cancer.
These diseases don’t have to be essential baggage of modernity. Anthropologists and (and some intrepid human evolutionary biologists) study modern day hunter-gatherer societies in order to glean information about the nature of our species pre-Neolithic Revolution. It’s important to note that these are not perfect models (cultural and biological evolution has still occurred in these hunter-gatherer societies), but are the best available. Interestingly, modern day hunter-gatherers don’t suffer from many of these mismatch diseases (This effect can’t be explained by longevity; hunter-gatherers regularly live into their late 60’s and 70’s. Though unusual to many of us, their lives aren’t as brutish as they are often portrayed). Diseases such as type-2 diabetes, hypertension, heart disease, osteoporosis, breast cancer and liver disease are rare among the societies. What’s more, myopia (near-sightedness), asthma, cavities, lower back pain, crowded teeth, collapsed arches, plantar fasciitis, and many other modern ailments are exceedingly rare. So what’s different? The easy answer is their diet, lifestyle, and environment. The difficult answer involves elucidating the physiological importance of certain social norms and biochemical processes of differing diets. Some very exciting work is beginning to arise in this field, dubbed “evolutionary medicine.”
Modern medicine and medical research focuses largely on treating problems, i.e., drugs and procedures that alleviate symptoms after the disease has manifested. While the cause is noble, and indeed necessary, it’s not enough. The childish logic of medical research creates a cycle of sickness-treatment that, in 2012, totaled almost $3 trillion in healthcare costs. Furthermore, the sedentary and Epicurean lifestyle in which many Americans live willingly feeds this cycle; among the less privileged, necessity feeds this cycle through the inability to afford healthy food, limited access to health education, and a sociocultural feedback loop that breeds its own vicious cycle.
There will likely never be a drug that can cure cancer (of which there are thousands of variants that can even differ between individuals who have the same variant), heart disease, type-2 diabetes, or many of the other previously mentioned noninfectious diseases. The rationale is akin putting water in your car’s gas tank and hoping additives will make it work as efficiently as gasoline. The car was built to run off gasoline. Similarly, your body has evolved to not eat an excessive amount of salts, carbs, and sugars (of which the different types, particularly glucose and fructose, do not have the same biochemical effects during digestion), sit for extended periods of time, wear shoes (particularly those with arch support; a common misconception is that arch support is good for you when, in fact, it weakens the muscles of the arch, leading to ailments such as collapsed arches and plantar fasciitis), read for several hours at a time, chew overly processed food, or many of the other things that people in developed nations commonly do, often times see as a luxury.
Modern medicine needs a paradigm shift. Funding needs to support not only treatments, but also investigations into prevention. The medical cause of diabetes may be insulin resistance, but what causes insulin resistance and how can we prevent it? Sugar may cause cavities, but what can do to prevent this? Shoes, even comfy ones, may cause collapsed arches, but how do we prevent this? The immediate response may be that this sort of prevention cannot be attained without abandoning modern technology all together. However, this isn’t the case, and it’s not the argument I’m trying to make. Research should focus on a broad range of interacting variable, including diet, work environment, school environment, and other aspects evolutionarily novel environments. Only after research from this evolutionary perspective takes place can constructive conversations and beneficial environmental changes occur. We don’t have to abandon modern society to be healthy; we just need to better understand how our lifestyle affects our bodies. Items such as smoking and alcohol are already age limited and touted as dangerous to health. Is junk food, particularly soda, any different? We don’t put age regulations on cigarettes or alcohol to protect bystanders. Instead, these regulations protect children who cannot be relied upon to make proper choices in their naivety. Should soda be under these same constraints?
If medicine and medical research does not undergo this paradigmatic shift and incorporate an evolutionary perspective, the outcome does not bode well for us. Medical costs will continue to rise with little room for improvement and greater opportunities for socioeconomic factors to play into the quality of healthcare available. This ad hoc treatment approach to medicine is not sustainable, and is not the best we can do.