ADVERTISEMENT
  About the SA Blog Network













Guest Blog

Guest Blog


Commentary invited by editors of Scientific American
Guest Blog HomeAboutContact

Patients and Evolutionary History

The views expressed are those of the author and are not necessarily those of Scientific American.


Email   PrintPrint



Evolution has revolutionized our modern scientific understanding of natural history and how our bodies came to be. Yet evolutionary insights regarding health and disease are not typically emphasized with patients.

Medical education focuses on proximate causes of disease — infection, trauma, cellular regulation, etc. — as opposed to evolutionary understandings of how our traits and responses came to be in the first place. What evolutionary insights are there for clinical medicine?

Medical conditions can occur when there is a mismatch between our evolved bodies and our particular society and environment. This idea challenges some of our notions of disease.

Hardly a day goes by when I don’t see patients with lactose intolerance, allergies, obesity, anxiety, near-sightedness, ADHD, and flu symptoms. The lactase gene spread rapidly in historical populations with dairy husbandry. But 70% of the world’s population is lactose intolerant, all of whom are “normal” in the context of their environments that were, until recently, lactose-free.

Allergies and autoimmune conditions are more common in developed societies where infections occur less frequently. This suggests a mismatch between our evolved immune system and our current environment. Recent evidence suggests that the incidence of autoimmune Crohn’s disease has risen in places where the incidence of gastrointestinal worm infection has fallen.

Obesity likely represents a mismatch between our food preferences which evolved in environments of relative food scarcity, and modern environments with increased food availability and decreased activity levels.

Anxiety may have been an evolutionarily useful response — think of the advantage of being jumpy when you hear rustling in the tall grass in an African savannah — but now may be an inappropriate expression for our current environment.

According to a recent study, children who are genetically susceptible to near-sightedness are less likely to become nearsighted if they spend more time outdoors.  This suggests near-sightedness may in part result from a mismatch between the outdoor environment in which we evolved and modern indoor activities such as reading and playing video games.

With an evolutionary perspective, conditions such as attention deficit hyperactivity disorder may be conveyed not as a disease, but rather a mismatch between a patient’s evolved nature and our particular society’s educational expectations. In all these conditions, an evolutionary approach helps clinicians and patients see medical conditions as contextual, rather than as an inherent defect. Evolution — natural history — becomes relevant.

Fever, cough, vomiting, diarrhea, etc. are evolutionary host defenses to expel infections, not, as patients often believe, infections themselves. Nonetheless the suffering can be marked. If treatment is provided to alleviate these symptoms, will our body’s defense against infections be weakened? This area is ripe for additional scientific research.

Like the early days of pharmacology and microbiology, it is too soon to predict the extent of clinical relevance that an explicit evolutionary understanding can yield. Evolutionary thinking has already directly impacted clinical medicine in areas such as genetics and vaccine design. Evolutionary principles also inform public health measures, such as the campaign to avoid inappropriate antibiotic use in humans and livestock to help prevent the evolution of resistant pathogen strains.

Just because a trait evolved does not make it good or bad. Evolution itself is impersonal and morally neutral.  It is up to us to provide deliberate values into the blind shuffle of evolutionary selection. An evolutionary scientific understanding provides greater wisdom into health and illness. Even in this world of technological marvels, the “history and physical” (H&P) is often emphasized as a physician’s most valued diagnostic strategy. In essence, evolution is history. With an evolutionary perspective, the “H” in “H&P” can be understood and appreciated at a deeper level.

Image: Genome.gov

Lawrence Rifkin About the Author: Lawrence Rifkin is a physician and a writer. Links to his writings on science, meaning, humanism, and medicine are at lawrencerifkin.wordpress.com. Follow on Twitter @LSRifkin.

The views expressed are those of the author and are not necessarily those of Scientific American.






Comments 3 Comments

Add Comment
  1. 1. Bill_Crofut 8:27 am 01/26/2013

    Re: “Like the early days of pharmacology and microbiology, it is too soon to predict the extent of clinical relevance that an explicit evolutionary understanding can yield. Evolutionary thinking has already directly impacted clinical medicine in areas such as genetics and vaccine design.”

    Biologist Prof. W. R. Thompson would seem to have been less enthusiastic about the alleged benefits of evolutionary understanding:

    “I do not contest the fact that the advent of the evolutionary idea, due mainly to the Origin, very greatly stimulated biological research. But it appears to me that owing, precisely to the nature of the stimulus, a great deal of this work was directed into unprofitable channels or devoted to the pursuit of will-o’-the-wisps….Really fruitful researches on heredity did not begin until the rediscovery in 1900 of the fundamental work of Mendel, published in 1865 and owing nothing to the work of Darwin….Much time was wasted in the production of unverifiable family trees….A long-enduring and regrettable effect of the success of the Origin was the addiction of biologists to unverifiable speculation. ‘Explanations’, of the origin of structures, instincts, and mental aptitudes of all kinds in terms of Darwinian principles, marked with the Darwinian plausibility but hopelessly unverifiable, poured out from every research centre.”

    [1956. Introduction. In: Charles Darwin. Origin of Species. Everyman Library No. 811. London: J. M. Dent and Sons. Reprinted with permission. Evolution Protest Movement. 1967. NEW CHALLENGING ‘INTRODUCTION' TO THE ORIGIN OF SPECIES. Selsey, Sussex: Selsey Press Ltd., p. 16, 17]

    Link to this
  2. 2. Tyler.j 9:31 am 01/27/2013

    Very interesting article! I have always said that ADD is not a disorder except maybe in extreme cases, but all I was going on was my own anecdotal evidence. My parents were pressured to put me on Ritalin by one or some of my teachers and it was suggested to me that I try it, I think I was about thirteen at the time.
    At first I marveled at my new found ability to sit totally still without losing my mind. Eventually however, I came to see that my “disorder” was actually the source of a lot of what made me an interesting/unique individual. I came to believe that this was a valuable part of who I am, like any attribute it has benefits and drawbacks. The fact that it is not cohesive with the structured, conventional style of teaching does not justify drugging children to bring them in line with the system. As with modern agriculture we think we can do away with nature or natural systems (the parallel being our own nature) and the results are often disastrous for the planet and for people. We need to teach children to embrace their differences, work their strengths and manage their weaknesses. I was simply bored in school, I never struggled. This lack of stimulation lead me to disrupt which lead to my being ‘put’ on Ritalin. This is a sad state of affairs. I wish I could tell every parent considering this option to seriously consider if their child is just bored, in which case I would suggest that stifling an eager mind is a terrible thing to do. Thanks a lot for this article which has strengthened my understanding and my argument. I realize there are many people with different situations and I’m not saying we need to do away with the drug, only that I think it is grossly over prescribed.

    Link to this
  3. 3. Tyler.j 9:37 am 01/27/2013

    “We need to teach children to embrace their differences, work their strengths and manage their weaknesses” forgot to add… giving kids drugs to make them like everyone else teaches them the exact opposite of this!

    Link to this

Add a Comment
You must sign in or register as a ScientificAmerican.com member to submit a comment.

More from Scientific American

Scientific American Holiday Sale

Give a Gift &
Get a Gift - Free!

Give a 1 year subscription as low as $14.99

Subscribe Now! >

X

Email this Article

X