But much of the stress we create today results from social conditions. So a lion chases you, that's a very stressful event, obviously, hopefully you managed to run away from the lion. Now normally, when we're stressed, the stimulus that causes the stress should be a short-lived one that's what evolution predicted. It just sets off this chain reaction that keeps going on and on. When you're stressed you crave unhealthy foods, but when you're stressed you also have a harder time sleeping, and when you have a harder time sleeping that elevates your levels of stress. Stress creates this vicious cycle, this positive feedback loop. On the way the stress we experience today is different from Paleolithic stress Lieberman serves as chairman of the department of human evolutionary biology at Harvard University. So people who have lives that contribute to higher basal levels of cortisol are more likely to suffer the ill consequences of that stress.ĭaniel E. So stress activates basic primal urges to eat calorie-rich food, which is, of course, useful to cope with those kinds of situations, from an evolutionary perspective. Cortisol makes us want to bring in more energy to cope again, with those energetic needs. And cortisol plays an important role because it releases sugar into the bloodstream so you can run from that lion or deal with whatever that bad situation is. If you jump out of an airplane or something really bad happens - a loved one dies - our body goes into a fight or fright state we're ready for danger. The hormone that gets elicited when you get stressed is cortisol. On why stress leads us to crave comfort foods We don't have the bodies that are able to cope with those kinds of levels of sugar, and the result is that we get sick.
But now we have access to abundant quantities of sugar and simple carbohydrates, which we evolved to love because they're full of energy, but we don't have the metabolism. So we love sweetness, but until recently, pretty much the only food that we got that was sweet was honey, and honey of course was a special treat - honey was pretty much the only form of dessert in the Paleolithic. Most wild fruits are about as sweet as a carrot. But if you try to eat foods that hunter-gatherers eat or chimpanzees eat, you'd be surprised at how unsweet they are. On our relatively "new," unfettered access to sweet foods In his new book, The Story of the Human Body: Evolution, Health and Disease, Lieberman traces these troubles back to their origins
It's a list of ailments big and small, including acid reflux, acne, anxiety, asthma, certain cancers, depression, Type 2 diabetes, flat feet, high blood pressure, irritable bowel syndrome, lower back pain and osteoporosis. He joins Fresh Air's Terry Gross to talk about some of the noninfectious diseases that may result from our Paleolithic bodies not being well-adapted to modern conditions. But Daniel Lieberman, professor of evolutionary biology at Harvard University, says that his field can help you understand why you got sick, and make you more aware of healthy and harmful behaviors. If you got sick, you probably wouldn't go to an evolutionary biologist to get treated.
Your purchase helps support NPR programming. Close overlay Buy Featured Book Title The Story of the Human Body Subtitle Evolution, Health, and Disease Author Daniel E.