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A moral case for evolution in medicine

I have been teaching evolutionary medicine (or EvMed to borrow the social media hashtag) at the bedside in the emergency department since 2000, and in the classroom since 2008. As a practical and academic enterprise, EvMed has made great strides during that time. It has been gratifying to see the birth of a scholarly society devoted to EvMed, the International Society for Evolution, Medicine and Public Health (ISEMPH) with well-attended yearly conferences. EvMed is featured in a journal, Evolution Medicine and Public Health, where I am fortunate to serve as an associate editor. At the same time, many medical students, even at my home institution, are taught little of evolutionary theory. My co-author Mark Schwartz and I wrote about why more evolutionary teaching is needed in medical school. We discussed reasons for slow uptake into medical school curricula, including religious reasons. More recently, emergency physician and educator Coffee Brown and I elaborated on those reasons. In a podcast, we asked why there is no love for evolution in medical school and discussed why is evolutionary medicine not more popular?

Early on, I thought that evolutionary thinking would be quickly adopted in medicine. I reckoned that because evolution is foundational in biology and therefore to medicine, evolution would rightly find its way into the medical mainstream. Later, I thought that showing the practical benefits of ev med would win the day. If we could just show how evolution has practical implications for antibiotic resistance and cancer chemotherapy, surely evolution would gain acceptance in medical school, right? Not so. Tellingly, most attendees of ISEMPH are not clinicians, and most don’t work at medical schools. I think now that theoretical and utilitarian reasons will never be enough to push evolutionary medicine into the mainstream. There also needs to be a moral case for evolutionary medicine.

Morality is where evolutionary biology has faced headwinds, mostly on religious grounds. Others have charged that evolutionary scientists have not sufficiently atoned for the unscientific and harmful misuse of evolution by eugenicists and racists in the last century. This is the indictment I will focus on. Recently the American Naturalist published Discussions of the “Not So Fit”: How Ableism Limits Diverse Thought and Investigative Potential in Evolutionary Biology. The authors, including a disabled scientist, argue specifically that teaching evolutionary medicine promotes ableism, continues to have a taint of eugenics, and makes disabled people feel inferior. I commend the authors for highlighting how evolutionary science and EvMed in particular might be perceived by disabled people. I acknowledge that this perspective is based on personal experience and the critique deserves thoughtful consideration. At the same time, I strongly disagree that teaching EvMed is morally fraught and something to be discouraged.

Before I explain why, I want to bring up the paper’s criticism of terms used in evolutionary biology – language that that they regard as supporting racism and ableism. For one of their examples, I agree with them. The term “purifying selection” is just creepy. We should swap an alternative phrase for that one. However, the authors also take issue with the terms “adaptive,” “fitness,” and “inclusive fitness.” They claim these terms are harmful for disabled people, even when they are defined technically, because they have negative connotations from their common use. I am not so sure. For example:

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Here we have the words adaptive, inclusion, and fitness, all used in the colloquial sense, in a way that is not harmful to disabled people

But I agree with the authors that language matters. I have argued that different terms in evolutionary medicine are needed for the sake of clarity. The common uses of these words simply overwhelm their technical meanings. Additionally, medical literature uses words like “adaptive” or “evolution” differently than an evolutionary scientist, as I described here. Moreover, we need specific terms just to find evolutionary medicine publications in search engines, such as PubMed, as I wrote in “Emergence of Evolutionary Medicine – publication trends from 1991 to 2010.” Until we settle on alternatives, confusion in language will be a barrier to progress, and we are stuck with what we have.

Beyond language, is evolutionary medicine harmful to disabled people? Having helped organize nearly every ISEMPH meeting since its inception, I can report that researchers in EvMed are committed to inclusivity and in relieving human suffering. We are not engaged in reinforcing human hierarchies. Society does plenty, by itself, to make life hard for many disabled people. Evolutionary medicine can be part of the solution to this problem. Here are 10 reasons why the project of evolutionary medicine improves the human condition for disabled and abled people.

  1. EvMed applies an adaptive and inclusive lens to the epigenetic modification of organisms. The capacity of for an organism to develop differently depending on the specific environmental conditions has been a major focus of evolutionary medicine. This effort explains human variation that results from developmental plasticity. Instead of pathology, some of this plasticity may be a functional response to an environmental challenge. At the same time, the evolved capacity for plasticity is an explanation for some social determinants of health; these play a role in the higher mortality from COVID-19, for instance, found in socially disadvantaged groups.
  2. EvMed rejects the dichotomy between normal and abnormal in clinical medicine. EvMed provides a basis for discarding the notion of one normal state, period. Instead, we evolved to be flexible. As an example, we wrote about why flexible regulation of body temperature during fever is protective. High blood sugar in sepsis also may not be the problem we think it is. In another example, having lots of inflammation is not all bad, and can help, for instance when interferon protects us against COVID-19.
  3. EvMed pushes back against the medicalization of expected life events, like menopause. There is an ongoing medical effort to treat menopause, and to supplement low T in men. Diagnosing these as “diseases” that would benefit from supplementation assumes a single threshold for what it means to be normal. That should be a red flag. EvMed points out that diagnosing normal conditions as diseases causes unintended harms. For more, see the post Life history theory and the microbiome.
  4. EvMed rejects the biological basis for race. Here I point you to evolutionary medicine pioneer Joseph Graves and Alan Goodman who wrote the excellent book Racism not Race, an expansive treatment of race as social construct, along with a thoughtful discussion of how natural selection and adaptation are vital for understanding health and disease in humans and other organisms.
  5. EvMed is skeptical of “dysfunction” and “dysregulation.” If any area of science is quick to assign pathology, it is medical science. Evolutionary medicine is a tool to push back against those who see dysfunction and dysregulation where it might not exist.
  6. Instead of defining any single optimal body type, EvMed proposes that different shapes may pay dividends in different conditions. I recently wrote: “If we view fat through the lens of pathology, we are blind to the adaptive function of fat.” It is popular to pathologize fatness, and to emphasize the burden of disease that accompanies excessive body weight. Especially when individuals are blamed for being fat, the notion that fat is a disease and a moral failing causes more, not less, human suffering. In addition to fat stigma, another issue with labeling fat as disease is that we can lose sight of why fat evolved in the first place.”
  7. EvMed can help you avoid a non-existent deficiency syndrome. EvMed expands our definition of what comprises a normal level of vitamin D, and of vitamin C, and normal levels of sex hormones. EvMed can be a corrective for pervasive medical “abnormalities” and “deficiencies” that aren’t.
  8. EvMed can be used to identify overdiagnosis and overtreatment. Examples include the unnecessary and harmful long term prescribing of proton pump inhibitors, and excessive screening practices that overdiagnose cancer without improving survival. EvMed considerations should be included as part of informed consent before starting any treatment, but especially experimental treatments.
  9. Disabled people commonly undergo procedures that predispose to infection with antibiotic resistant organisms. Researchers applying EvMed principles developed strategies to prevent or mitigate resistance, by minimizing the dose or duration of antibiotic, or by using phage therapy. These strategies promote antibiotic stewardship goals and can be life saving.
  10. EvMed has embraced One Health, which highlights the shared evolutionary legacy of life on Earth. One Health seeks to bridge the gap between human and veterinary medicine. Human diseases are not unique to us; they have analogs in other species. Identifying those commonalities can illuminate why we have disease vulnerabilities and how we can prevent suffering in humans and other animals.

To summarize, evolutionary medicine is more inclusive of human variation than is medicine as conventionally taught. EvMed rejects the simple dichotomy between normal and abnormal. Differences are often applauded, not pathologized. Even more often than differences, EvMed is concerned with commonalities, features that all humans share, as a result of common descent and the legacy of natural selection. Importantly, EvMed is finding solutions to intractable problems like antibiotic resistance, and thereby reducing suffering. These provide the moral case for doing more, not less, evolutionary medicine teaching, researching, and translating EvMed concepts to the clinic.

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