Slate has an interview with evolutionary biologist Daniel Lieberman, who explains the paradox between exercise being good for us and it feeling like a chore.
Q: What are the consequences of the modern sedentary lifestyle?
DL: It’s hard to think of one disease that is not affected by physical activity. Take the two major killers: heart disease and cancer. The heart requires exercise to grow properly. Exercise increases the peripheral arteries and decreases your cholesterol levels; it decreases your risk of heart disease by at least half.
Breast cancers and many other reproductive tissue cancers also respond strongly to exercise. Other factors being constant, women who have engaged in regular vigorous exercise have significantly lower cancer rates than women who have not. Colon cancer has been shown to be reduced by up to 30 percent by exercise. There are also benefits for mental health—depression, anxiety, the list is incredibly long.
Q: What can we do about our maladaptive traits?
DL: If we want to practice preventive medicine, that means we have to eat foods that we might not prefer, and exercise when we don’t want to. The only way to do that is through some form of socially acceptable coercion. There is a reason why we require good food and exercise in school—otherwise the kids won’t get enough of it. Right now we are dropping those requirements around the world.
Q: Being able to run is one thing—how did we then go on to become endurance athletes?
DL: We evolved from very non-active creatures. A typical chimp will walk 2 to 3 kilometers a day, run about 100 meters and climb a tree or two. Your average hunter-gatherer walks or runs 9 to 15 kilometers per day, and we have all these features in our bodies, literally from our heads down to our toes, that make us really good at long-distance walking and running.
I and my colleagues at the University of Utah, Dennis Bramble and David Carrier, think the key advantage for humans was persistence hunting, whereby you run very long distances to chase animals in the heat and run them into heat stroke. We can run for very long distances, marathons in fact, at speeds at which other animals have to gallop. That’s not an endurance gait for quadrupeds, because they cool by panting—short shallow breaths. You can’t pant and gallop at the same time. If you make an animal gallop in the heat for 15 minutes or so, on a hot day, you’ll kill it.
Q: But we have adaptations for this kind of endurance running?
DL: Yes. Our bodies are loaded with all kinds of features: short toes that require less energy to stabilize and generate less shock when running; the Achilles tendon that stores and releases energy appropriately as we run; the large gluteus maximus muscles that steady the trunk; and stabilization of the head. I’m a middle-aged professor, I’m not a great specimen of an athlete, but I can easily run a marathon at a speed that would cause a dog my size to gallop.