Known as the “barefoot professor,” Daniel E. Lieberman, a human evolutionary biologist at Harvard, has been researching answers to quirky questions such as: How did we evolve to throw footballs? How has our diet altered our head size? Do sneakers negatively impact our locomotion?
He believes taking an evolutionary approach to human anatomy and physiology could help to eventually prevent not only athletic injuries — he is a barefoot runner — but also diseases, including diabetes and osteoporosis, that were unheard of in prehistoric times. His new book, “The Story of the Human Body,” outlines the divergence between the ways our bodies slowly evolved over millennia and the rapid rise of modern inventions such as white bread, cars, and antibiotics.
Q. Are we making net gains or net drawbacks from culturally changing faster than our genes?
A. People are living longer and dying less of infectious diseases, so it’s likely a net gain, but we’re also suffering from more chronic diseases. We musn’t confuse the diseases that occur in old age from the ones caused by old age. In that regard, we can do better to prevent the first kind.
Q. In your book you list nearly 50 diseases and conditions, from Alzheimer’s disease to stomach ulcers, that developed because our genes couldn’t adapt quickly enough to our changing environments. Can you explain more about these so-called “mismatch diseases”?
A. It’s been appreciated for a while that a lot of diseases today are at least somewhat mismatched and that about 70 percent of these diseases are preventable.
We inherited a physiology that causes us to crave sugar and calorie-rich foods and to be extremely good at storing energy in order to use it for inevitable periods of food shortage. But we never evolved to have to lose weight because that was never a challenge for our ancestors. In an environment of plentiful, inexpensive, tasty food that’s loaded with sugar and calories, we’re ill equipped to cope, which has led to a rise in certain cancers, diabetes, and heart disease.
Our bodies also need the stress of physical activity for muscles to get bigger and bones to grow; those who are less active when they’re young attain a smaller skeletal mass, which increases their risk of osteporosis later on. Even our jawbones don’t get enough stress from the softer more processed foods we chew which has likely led to a rise of dental crowding and impacted wisdom teeth.
Q. Don’t genes play a role in many of these diseases?
A. Some of us have ancestors who were less adapted genetically to metabolizing carbohydrates, which has raised our susceptibility for diabetes. In fact, a lot of genes have been identified for chronic diseases, but these genes tend to have only a small effect and tend not to be very common. It’s far more likely to be a changing of our environment rather than a change in our genes that’s accounting for the rise in these illnesses.
Q. How can we change our environment in the modernized world we live in?
A. It’s all about tradeoffs, and we can’t escape them. More of us are near-sighted from working indoors all day in front of computer screens, but we have glasses to fix that. On the other hand, we have to make it easier to grab the celery stick instead of the chocolate chip cookie or to take the stairs in the mall instead of the escalator. We need to be mindful of how our bodies are not able to cope with physical inactivity and a glut of food.
Q. You write in the book that “a little dirt never hurt.” Do you think that we’re paying a price for waging a war against germs?
A. Antibiotics and vaccinations are lifesaving, but nonetheless, we do pay a price for making life so easy all the time for our immune systems. One may be that our immune systems are acting like teenagers that don’t have enough stuff to do and are more likely to get into trouble and start attacking our cells and proteins. Having a healthy microbiome — healthy bacteria in your gut — instead of constantly nuking them with antibiotics, and having a healthy exposure to germs and worms essentially can in some regards promote health. Maybe in the future when you get an antibiotic, you can follow it up with the appropriate probiotic to recolonize the healthy bacteria that you need. But more research needs to be done on this.
Q. What do you think about the Paleo diets that have become so popular?
A. There are some good aspects to the Paleo diet such as its emphasis on low-carb, low-sugar foods that aren’t processed. But there are reasons to be skeptical of its focus on red meat and animal protein. Our ancestors didn’t evolve to be healthy — only to successfully reproduce — and just because our ancestors did something during the Paleolithic period doesn’t mean we should go back to those habits.
In fact, most societies were able to develop nutritious diets after switching from hunting and gathering to farming. The Mediterranean diet, Japanese diet, and traditional Mexican diet all focused on plenty of vegetables, fish, and grains.
Q. Are the solutions basically to eat better and exercise more?
A. That’s about 80 percent of it. The book is about why your grandmother was right. It’s not a secret that eating nutritiously and exercising are important for good health. They don’t guarantee it, but they raise the chances.