The Scholarly: Future clinicians are generally not taught evolutionary explanations for why our bodies are vulnerable to certain kinds of failure. The narrowness of the birth canal, the existence of wisdom teeth, and the persistence of genes that cause bipolar disease and senescence (aging) all have their origins in our evolutionary history. Powerful insights from evolutionary biology generate new questions whose answers will help improve human health.
By looking at how our ancestors lived, loved, got sick, and got well for millions of years, evolutionary medicine offers us a natural plan for living longer, healthier, and happier lives today.
Until Saturday morning, when I read, "How to Stop Coughing" in the Chicago Tribune blog I never thought about what coughing had to do with evolution---that it is nature's way of making sure viruses find new homes, and that phlegm was meant to be swallowed.
That's Dr. William Meller's evolution medicine spin on "the common cough" in his "soon to be published" book, Evolution Rx. His book is the lay/"lite" version of evolution medicine, a new-to-me basic science that's now part of some medical school curricula, & the subject of a 2009 National Academy of Sciences/NIH meeting.
What is Evolution Medicine?
It's the convergence of anthropology, genetics and medicine & it gives a greater respect to the body & the ways the body has evolved to take care of itself. Many of our 21st century diseases have their roots in our evolution--and exist because we now live in an environment that our bodies weren't designed to handle.
An understanding of why our bodies are designed as they are, coupled with a knowledge of the genetic variations that have evolved enables physicians & scientists to better design treatments for disease---and more practically---it helps us to understand why under certain conditions we are bound to get stressed-depressed-anxious, have allergies, autoimmune diseases, miscarriages, back aches, arguments with our adolescent kids, diabetes, weight gain and more.
If we know the whys--we are in much better shape to do something about it!
Here's just a sampler: It's actually a bookmark for my own future reading.
Scholarly Evolution Medicine & Happiness--Depression--Anxiety
"Our brains could have been wired so that good food, sex, being the object of admiration, and observing the success of one's children were all aversive experiences. However, any ancestor whose brain was so wired would probably not have contributed much to the gene pool that makes human nature what it is now.
Similarly, if there were someone who experienced no upset at failure, no anxiety in the face of danger and no grief at the death of a child, his or her life might be free of suffering but also would probably be without much accomplishment, including having offspring.
These evolved preferences for pursuing certain resources and avoiding their loss are at the very centre of human experience."
"It is not surprising that bad feelings are reliably aroused by losses, threats of losses, and inability to reach important goals." (Emmons, 1996)
Source: Nesse, RM., "Natural selection and the elusiveness of happiness" Phil Trans R Soc. Lond B 359(1333-1347, 2004)
Lite Evolution Medicine on Gossip
"Gossip is a form of trade. Anyone who shares gossip is letting us know they are willing to reveal risky information, something that may protect us in the right circumstances. Hinting at secrets tells others that we hold something valuable to them. This marketplace of information can benefit us individually and the group as a whole." William Meller. Evolution Rx.
Scholarly Evolution Medicine on Health
Coughs, Fever & Diarrhea: "There's growing recognition that cough, fever, and diarrhea are useful responses shaped by natural selection, but knowing when is it safe to block them will require studies grounded in an understanding of how selection shaped the systems that regulate such defenses and the compromises that had to be struck." Not always such a good idea to stop the diarrhea with Imodium--lower the fever down to normal--or suppress the cough or spit out the phlegm.
Obesity: "The epidemic of obesity can be interpreted in terms of the evolutionary forces that shaped dietary preference and appetite regulation." We've evolved to love the taste of fat & sugar & to eat as much as we can--you never know when the next famine will hit and now we're stuck in the middle of a giant smorgasbord.
Low Back Pain: "Evolution is also the origin of apparent anatomical anomalies such as the vulnerabilities of the lower back." So that's why 80% of us get lower back aches! Why were our backs designed this way? Maybe we aren't supposed to work in offices.
Breast Cancer: "Increases in breast cancer have been attributed to hormone exposure in modern women, who have four times as many menstrual cycles as women in cultures without birth control." How can we lower our bodies' exposure to so much estrogen? Longer breast-feeding? Eating less fat? Avoiding hormones in milk & meat, or from exposure to endocrine-disrupting plastics?
Breast Cancer: "Studies suggest that nighttime exposure to light increases the risk of breast cancer by inhibiting the normal nighttime surge of melatonin, which may decrease tumor growth." Dim those lights in the evening.
Infertility & miscarriage: "Evolution has provided some explanations for conditions such as infertility. The process that eliminates 99.99% of oocytes may have evolved to protect against common genetic defects. And some recurrent spontaneous miscarriages may arise from a system evolved to protect against investing in offspring with combinations of specific genes that predispose to early death from infection.
Genetic Diseases: "..Evolutionary factors are responsible for certain genetic diseases...and the textbook example is sickle-cell disease, whose carriers are resistant to malaria." Nature is far from perfect & there's often a trade-off.
Autoimmune Diseases and Parasites: We evolved in an environment where we were frequently exposed to severe, persistent infections and most of us carried parasitic worms, most of the time. Turns out the worms down-regulated our immune response to enhance their own survival and in turn that reduced our susceptibility to automimmune diseases by reducing the overall production of antibodies. Today, our environment is so antiseptic that few of us have worms and few adults die from infections, but many have autoimmune diseases now that children rarely have parasites. Some doctors are successfully treating autoimmune disease by injecting a preparation made with the parasitic worms. And children with schistosomiasis (a worm) & nematodes have less asthma or dust mite allergies.
There's So Much More: Like why low birth-weight babies are prone to future diabetes & obesity; lactose intolerance; the prevalence of nearsightedness; antibiotic resistance; Vitamin D deficiency, lack of sun exposure & the increase in cancer, diabetes & osteoporosis; why suppressing stomach acid contributes to a rise in ulcers & c. Difficile.
Source: Evolution in Health & Disease. 2nd ed. Stephen C. Stearns and Jacob C. Koella Oxford University Press, Nov. 22, 2007.
To read more scholarly materials, click here and here and here
To listen to some short talks on the subject, click here
Be sure to check out Robert Sapolsky's Stanford lectures on stress--fascinating material. They're each 1 hour long, so it's much better to download them through iTunes & listen to them on a walk:
"Why Zebras Don't Get Ulcers"
"Stress and Coping: What Baboons Can Teach Us"
Both are available free at Stanford at iTunes U if you want to download them to your IPOD.
Lite Evolution Medicine on Health
Attention Deficit Disorder
"Attention deficit hyperactivity disorder (ADHD) probably evolved as a beneficial survival trait serving to protect our Stone Age ancestors in the dangerous conditions of daily life in the Stone Age. When danger lurked around every rock and a carnivorous feline could leap out of the nearest tree at any moment, being highly alert and easily distractable, probably saved our ancestors lives on a daily basis."
"Conventional wisdom would have it that we cough when we are sick to “clear” our throats and lungs of bad stuff. We commonly think of mucus and phlegm as something we need to get rid of. Long before we knew of viruses and bacteria and germs of all sorts, we associated all that gooey stuff with the cause of our being ill. But it is part of the cure.
Our bodies have evolved this complex stuff known as phlegm to engulf the germs that have taken root in us and it works best when it is inside of us. Making us cough is actually the evolutionary strategy of the virus to escape from us and move on to the next victim. We know that cold and flu viruses are spread by airborne droplets…of mucus spewed out when we cough. When we are told to “cough it up” we are the unwitting accomplices of our enemies.
But what happens to all that goop if we don’t cough? It gets absorbed in our lungs, and swallowed into our stomachs where our immune systems can react quickly and target the invader to eliminate it. Even worse is the consequence of all that coughing. We do harm to our throats. And our lungs. When we have a tickle in our throats, clearing them and coughing is like scratching an itch.
But just like scratching, when we do it too much, it leads to more swelling, not less. And more swelling, means as it does everywhere in our bodies, more pain. And more coughing. I often see patients in the office who have largely recovered from a cold but days and weeks later are still complaining of sore throats, frequent throat clearing and a persistent cough. As I explain the above scenario to them, I show them how to not cough, by swallowing, drinking, and coughing with a closed mouth or into their sleeve. Within a day or so they are often so much better that they don’t need any of those colorful cough medicines and lozenges and rubs that they have been fruitlessly trying."
Source: The Evolution Rx Blog by Dr. William Meller
While the lite version is certainly more readable, I'm sticking to the scholarly version. There are so many nuances here, different populations of people to consider, different gene variants, and even the experts say there's still so much more to be learned.
Bottom Line: We've evolved to a state that is "often mismatched to our modern environment because that environment is changing more rapidly than we can adapt to it."
Better to make sense of why our bodies were designed the way were, and then figure out how best to "play the hands we are dealt."
In the meantime I'm ditching the milk, sticking to whole foods, taking breaks from my office desk, dimming the lights in the evening, and getting more sunlight for starters! Maybe I should be glad I had pin worms as a kid!