An evolutionary perspective predicts that most diets and fitness programs will fail, as they do, because we still don’t know how to counter once-adaptive primal instincts to eat donuts and take the elevator. Further, because the body is a complex jumble of adaptations, all of which have costs and benefits, and some of which conflict with one another, there is no such thing as a perfect, optimal diet or fitness program. Our bodies are full of compromises.
The Story of the Human Body: Evolution, Health, and Disease
by Daniel Lieberman
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We didn’t evolve to be healthy, but instead we were selected to have as many offspring as possible under diverse, challenging conditions. As a consequence, we never evolved to make rational choices about what to eat or how to exercise in conditions of abundance and comfort.
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Our body’s evolutionary journey is also far from over. Natural selection didn’t stop when farming started but instead has continued and continues to adapt populations to changing diets, germs, and environments. Yet the rate and power of cultural evolution has vastly outpaced the rate and power of natural selection, and the bodies we inherited are still adapted to a significant extent to the various and diverse environmental conditions in which we evolved over millions of years. The end product of all that evolution is that we are big-brained, moderately fat bipeds who reproduce relatively rapidly but take a long time to mature.
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The fundamental answer to why so many humans are now getting sick from previously rare illnesses is that many of the body’s features were adapted in environments from which we evolved, but have become maladapted in the modern environments we have now created. This idea, known as the mismatch hypothesis, is the core of the new emerging field of evolutionary medicine, which applies evolutionary biology to health and disease.
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