Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. The goal of evolutionary medicine is to understand why people get sick, not simply how they get sick. Modern medical research and practice has focused on the molecular and physiological mechanisms underlying health and disease, while evolutionary medicine focuses on the question of why evolution has shaped these mechanisms in ways that may leave us susceptible to disease. (1)
Nothing in medicine makes sense except in the light of evolution
Darwinian medicine encompasses several theories, concepts, and principles, all of which are tied together by a rope in the form of evolutionary science. Humans, like all other organisms on this planet, are a product of evolution. There is a reason why our bodies work the way they do; a reason why we do better on some diets than others; and a reason why we sometimes get sick. To find these reasons, we need to look back and examine the evolutionary processes that got us to where we are today.
This quote from a review paper on Darwinian medicine nicely summarizes how evolutionary theory can enhance our understanding of health and medicine:
Prudence dictates that it is high time medicine broadened its scope beyond an evidence-based epistemology. The evidence-based methodologies are focused primarily on immediate problem-solving and proximate causation. Medicine must embrace the evolutionary paradigm that welcomes ultimate explanations as espoused in evolution into its epistemology. Through this door will enter into medicine the concepts of systems biology, dynamical systems theory, complex systems, complex networks, and chaos theory, to name some up-and-coming analytical methodologies that should pry medicine out of its linear thinking. Because H.s. sapiens is the product of an evolutionary process, we cannot hope to have a deep understanding of the major diseases of our age if we ignore our evolutionary past. In the depths of our minds as in our genes, we are all African hunter-gatherers. (2)
Evolutionary science to the rescue
There’s an evolutionary explanation for “everything”. Sometimes, this explanation presents itself quickly and clearly, whereas other times, we have to dig long and hard before we find the answers we’re looking for. In the end, though, the explanation can usually be found via the evolutionary route. It may not be fully formed and explain everything we need to know, but it gives us a foundation upon which we can build our ideas and understanding.
Below are some of the many medical-related questions that evolutionary theory can help us answer:
- Why does antibiotic resistance develop?
- What types of diets are different organisms adapted to eat?
- Why does our body temperature tend to rise when we get an infection?
- Why are humans so susceptible to develop back and knee problems?
- How and why do some gut organisms “hijack” our brain?
- Why are many diseases and health problems more prevalent today than they were in the Paleolithic?
- What type of microbiota is the human body adapted to harbor?
- Why do we think and act the way we do?
- Why isn’t the human body “perfectly” designed?
- Why and how do cancer cells evolve and spread?
The immense power and reach of Darwinian medicine
One of the greatest strengths of Darwinian science in the context of health and disease is its ability to bring together and consolidate the different branches of medicine. It won’t generate quick fixes to all of the medical problems we face or dramatically change emergency care; however, it bestows us with a set of principles which together form a framework by which all of medicine can be organized, refined, and sustained, as highlighted by the illustration below.
The science of Darwinian medicine: 12 things you need to know
The field of Darwinian medicine is built on a solid foundation of scientific data. Below is a summary of some of the most important things we’ve learned over the most recent decades.
- Hunter-gatherers and non-westernized, traditional people are lean and fit and rarely develop chronic degenerative diseases (3, 4, 5), which could largely be explained by the fact that they live in environments that resemble Paleolithic, natural environments, often considered to be the Environments of Evolutionary Adaptedness (EEA) for humans (6, 7). This is not to say that we stopped evolving with the Neolithic Revolution or that we should abandon all modern foods, lifestyle habits, and medical innovations. It simply means that we should always keep in mind that we are still – to a significant extent – adapted to live as hunter-gatherers in the wild.
- Many human diseases and health problems, including acne vulgaris, type-1 diabetes, heart disease, obesity, and the metabolic syndrome, are caused, in large part, by evolutionary mismatches (i.e., mismatches between the human genome, which is comprised of genes selected in the past, and the modern milieu, which differs markedly from past environments) (3, 4, 5, 8, 9).
- Cancer evolves via natural selection (10). In order to understand how cancer cells develop and spread, we must first understand the game of evolution.
- Humans’ microbial environment has changed dramatically over the past 10.000 years (10, 11). These changes have contributed to increasing the incidence and prevalence of many health disorders, in particular disorders that are associated with chronic inflammation (10, 11).
- Modern, imprudent diets change the gut environment in such a way that a microbiota that is incompatible with human genetics develops (12, 13, 14). These changes occur as a result of selective processes in the gut; when the environment changes, the microbiota also changes; those microbes that are best adapted to survive and reproduce under the new conditions proliferate, whereas those that are poorly adapted wither or die.
- Paleolithic, hunter-gatherer style diets are effective in the treatment of many health problems (15, 16, 17, 18).
- Contemporary humans who move into the wild for a period of time and adopt a hunter-gatherer style lifestyle experience rapid health improvements (19, 20).
- Genome-microbiome mismatches, caused by recent changes in humans’ environment, underlie a long list of diseases and health problems (12, 13, 21, 22).
- Humans’ physical activity requirements were determined in the past. Many human diseases and health problems, in particular conditions associated with the bones, cardiovascular system, and/or muskuloskeletal system, such as osteoporosis and heart disease, are partly caused by the replacement of a physically active hunter-gatherer lifestyle with a sedentary, modern lifestyle (23, 24).
- Humans’ propensity to develop health problems such as back pain may partly be explained by the occurrence of trade-off situations earlier in human evolution. When our ancestors started to walk upright, they became better at some things, such as looking over tall grasses, but worse at other things, such as climbing. They may also have become more prone to develop certain musculoskeletal problems.
- Humans didn’t evolve as single entities; we evolved alongside a cloud of microbes. A growing body of evidence suggests that a progressive loss of biodiversity (biome depletion) from the human superorganism, starting about 10.000 years ago, with the transition from hunting and gathering to agriculture, is at the root of a long list of health problems (10, 11, 25). Biome reconstitution, guided by evolutionary thinking, is a key measure required to slow down and reverse the increasing incidence of immune-related health problems in the modern world (10, 11, 25, 26).
- All organisms on this planet are a part of an evolutionary arms race. In order to understand why and how some microbes infect our bodies and cause us harm, we first need to understand the rules of the game of evolution.
Darwinian medicine doesn’t just help inform us about why we get sick, it’s also of great practical use. The Paleo Physicians Network, a network that aims to provide a simple interface between health conscious consumers and medical professionals who practice Darwinian/evolutionary medicine, expresses the following about the practical applications of Darwinian medicine:
Despite the advances of modern medicine the pharmo-centric approach has failed to address the complex degenerative diseases plaguing Western societies. “Magic Bullets” for cardiovascular disease, neurodegeneration, cancer and infertility are oddly lacking given our remarkable understanding of the pathogenesis of these and other diseases. Unlike infectious disease, Western degenerative diseases do not lend themselves to simple pharmaceutical solutions. The limitations of modern medicine lie not in a lack of technology or understanding of disease process, but in an epistemological framework consistent with complex biological systems. To be effective, modern medicine must adopt the same framework the rest of the biological sciences have benefited from for over 100 years: Evolution via Natural Selection.
For non-emergent (life threatening) situations the first intervention for most issues should derive from an Evolutionarily consistent framework including, Paleo Nutrition, sleep patterns, socialization, and exercise which is consistent with the processes which formed the H. Sapien genome. (27)
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