Until extremely recently, you couldn't live, you couldn't survive as a human being without being an endurance athlete. Not just hunting and gathering requires athleticism but also being a farmer. Subsistence farmers have to work extremely hard. Until the invention of industrialized machinery, farmers had to work even harder than hunter-gatherers, often spending many thousands of calories a day. They have to dig ditches and throw vast quantities of hay into bales and they have to schlepp stuff all over the place. Farmers had to work brutally difficult, hard, exhausting lives. It wasn't until, again, the invention of new technologies such as domesticating animals or even more recently machinery such as the internal combustion engine, that farmers were able to live non-grueling lives. It's only in the last 100 years, in fact maybe for many people the last 20, 30, 40, 50 years, that human beings have been able to lead extremely sedentary lives without any physical activity. A typical American today living in a post-industrial information technology world can get up in the morning, reach to the cabinet, get breakfast cereal that's in a box, pour it, reach to the refrigerator, pour some milk in there. He or she can spend his or her entire day without ever elevating his heart rate or her heart rate. You can sit in wheelie chairs all day long, take an elevator to your floor, sit in a chair all day long staring into a computer, and drive home from work. Dinner basically involves pressing a few buttons, or if you have to go to the supermarket, wheeling around a cart. Human beings today don't have to engage in physical activity anymore. It's natural and normal for us to think that the world around us is normal. But our world, our lives today are profoundly abnormal, especially in the case of no longer having to use physical activity as part of our daily routine. We've also got this bizarre notion that finally came true, that our bodies don't really matter. Think about St. Thomas Aquinas, who believed that the flesh was irrelevant and that all that really mattered was your soul. But only monks and rich clerics in Europe could get away with that kind of opinion in the Middle Ages, because everybody else had to work like a dog. But now, your average human being can live a life of ease and luxury, much more physically inactive than even kings and queens of Europe in the old days. We've finally been able to realize St. Thomas Aquinas's dream of basically ignoring the flesh, ignoring the body. The result is an epidemic of obesity and heart disease and various kinds of cancers such as colon cancer and breast cancer that largely come from physical inactivity combined with a really loathsome diet.