Born, and Evolved, to Run
Among his academic peers, Daniel Lieberman, 47, is known as a “hoof and mouth” man.
That’s because Dr. Lieberman, an evolutionary biology professor at Harvard, spends his time studying how the human head and foot have evolved over the millenniums. In January, Harvard University Press published his treatise, “The Evolution of the Human Head.”
We spoke in a Cambridge hotel room for three hours last winter and then again on the telephone in June. An edited and condensed version of the two conversations follows.
Q. Why heads?
A. Our heads are what make our species interesting. If you were to meet a Neanderthal or a Homo erectus, you’d see that they are the same as us — except from the neck up. We’re different in our noses, ears, teeth, how we swallow and chew. When you think about what makes us human, it’s our big brains, complex thought and language. We speak with our heads, breathe and smell with our heads. So understanding how we got these heads is vital for knowing who we are and what we are doing on this planet.
Q. Are there any practical benefits to your research?
A. There are. A majority of the undergraduates who register for my evolutionary anatomy and physiology class here at Harvard are pre-medical students. Learning this will help them become better doctors. Many of the conditions they’ll be treating are rooted in the mismatch between the world we live in today and the Paleolithic bodies we’ve inherited.
For example, impacted wisdom teeth and malocclusions are very recent problems. They arise because we now process our food so much that we chew with little force. These interactions affect how our faces grow, which causes previously unknown dental problems. Hunter-gatherers — who live in ways similar to our ancestors — don’t have impacted wisdom teeth or cavities. There are many other conditions rooted in the mismatch — fallen arches, osteoporosis, cancer, myopia, diabetes and back trouble. So understanding evolutionary biology will definitely help my students when they become orthopedists, orthodontists and craniofacial surgeons.Continue reading the main story
Q. Your other specialty is the evolution of the foot. Why this emphasis on the farthest points of our bodies?
A. Actually, I’m interested in the entire body. However, I got into feet because of my interest in heads. Some years ago, I was doing an experiment where I put pigs on treadmills. The goal was to learn how running stressed the bones in the head. One day, a colleague, Dennis Bramble, walked into the lab, watched what was going on, and declared, “You know, that pig can’t hold its head still!”
This was my “eureka!” moment. I’d observed pigs on treadmills for hundreds of hours and had never thought about this. So Dennis and I started talking about how, when these pigs ran, their heads bobbed every which way and how running humans are really adept at stabilizing their heads. We realized that there were special features in the human neck that enable us to keep our heads still. That gives us an evolutionary advantage because it helps us avoid falls and injuries. And this seemed like evidence of natural selection in our ability to run, an important factor in how we became hunters rather than just foragers and got access to richer foods, which fueled the evolution of our big brains.
So I got interested in how we developed these stable heads. I’m a runner myself. It’s always interesting to study one’s passion. By 2004, we’d found enough evidence to publish a paper in Nature where we declared, “Humans were born to run.” We cited the many dozens of adaptations in the human body that had made us into superlative endurance runners, even compared to dogs and horses.
Before bows and arrows and before horses were tamed, we did “persistence hunting” where we ran kudu, wildebeest and zebra into exhaustion. These animals can’t pant when they gallop. They overheat. People would find a big animal and chase it till it collapsed. You need no technology to do this, just the ability to run long distances, which all of us have.Photo
You can see proof of this capability every November when 45,000 people run for many hours through the streets of New York.
Q. People with bad backs often blame evolution for their pain. They say, “My back aches because man was not meant to walk on two feet.” Are they right?
A. If that were true, natural selection would have its toll and we’d be extinct. What is more likely is that many people sit in chairs all day, get no exercise, and thus have weak backs. We did not evolve to sit in chairs all day.
Q. In your lab, you study the phenomenon of barefoot running. How did that become part of your portfolio?
A. About a year after the Nature paper came out, I gave a public lecture where this bearded guy, with only socks and duct tape on his feet, came up to me and said, “I don’t like to wear shoes when I run — how come?” He’d become a barefoot runner because his feet hurt in shoes. The man was “Barefoot Jeffrey,” a Harvard grad who owned a bicycle shop in Jamaica Plain. What a great question!
Obviously, people had run barefoot for millions of years before shoes, socks, Nikes. I’d sometimes wondered if some of the sports injuries that runners get are related to an issue connected to how people run in shoes — the heel strike, it’s called. When most of us run, we land hard on our heels, and that causes a shockwave and it travels up your leg and eventually hits your head, which jiggles really fast. Those of us who wear shoes think that’s normal, to land with a big jolt.
So I asked Barefoot Jeffrey to come to the lab and show me how he ran. He ran in this beautiful way that was completely collision-free. Light as a feather. When he hit the ground, he didn’t land on his heel. Instead, he landed on the ball of his foot, and there was no shock wave that hit his head. That led us to producing another paper in Nature where we actually studied barefoot runners like Jeffrey.
We also went to Africa and went to people who’d never worn shoes. What we discovered was that people who run barefoot tend to run differently than people who wear modern shoes; they run in a much lighter and gentler way because it would hurt to run the way people do in shoes.
Q. And what’s the value to knowing this?
A. To prevent sports injuries. We think that one reason runners crash into the ground is because the shoe makes it possible to hit the ground hard. My lab is currently studying the Harvard track team to measure if runners who use a barefoot style are injured less than runners who land on their heels.
Q. Do you run barefoot?
A. Only in the summer. Obviously, you cannot run barefoot in a New England winter! Then, I use a shoe that brings me more toward the barefoot style. It’s called a “minimal shoe,” and it’s more like a glove for the foot. Some people tell me it looks silly. But I like the way it feels. And I love running barefoot when I can. You get all this wonderful sensory pleasure from your feet. You feel the grass and the sensation of the earth. You get bathed by sensation. There are a lot of sensory nerves in the feet.
Right now, every sports gear company is now developing a line of these minimal shoes. One company, I should inform you, has helped fund some of my laboratory research, though I’ve not had anything to do with their product.
Q. Is your research part of a trend?
A. It’s part of this movement to try to listen to evolution in our bodies. We evolved to eat different diets, to run differently and live differently from the ways we do today. People are looking to evolution to find out how our bodies adapted and what might be healthier for us. That’s good.
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