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Daniel E. Lieberman is the chair of the Department of Human Evolutionary Biology and professor of biological sciences.
This interview has been edited for length and clarity.
FM: You’re a biological anthropologist. Those words — biology and anthropology — are not usually seen together. Can you describe the methods of your field?
DEL: Biological anthropology, which at Harvard we call human evolutionary biology, is just really the study of human biology, at every level, from genes all the way up to environments, but we use an evolutionary lens to think about how and why humans are the way we are. Here at Harvard and in my lab, we take a body-focused approach. We’re interested in what were the major transitions that occurred in human evolution that made us the way we are.
FM: I notice a lot of skulls decorating your office. How do you test a hypothesis made from studying fossils and human remains?
DEL: Well, that’s the fun of this field, right? You can’t just do an experiment and replicate human evolution in the lab. We have to combine many different lines of evidence to test hypotheses.
We use the fossil record. Of course, you can make hypotheses about how to interpret the fossil record and what happened in the fossil record. We look at genetic evidence, we look at physiological evidence, we do experiments in the lab on people’s biomechanics and physiology and test models, we look at epidemiological data on health. When you combine evolutionary theory and combine different kinds of evolutionary data, you can test hypotheses in a very comprehensive way.
FM: The Human Evolutionary Biology department holds really strong to the idea that, “nothing in biology makes sense, except in the light of evolution.” Can you tell me about the history of this quote, and the ideas that it captures?
DEL: That quote was written by a very famous biologist named Theodosius Dobzhansky. It was in an essay to high school teachers — actually, it was the title of the essay. The basic argument that he articulated beautifully in that essay — it was not a new idea, but he articulated better than I think anybody had before — is that humans weren’t designed, we weren’t engineered. We evolved. If you want to understand why we are the way we are, you have to include that evolutionary history as part of your perspective.
FM: You’ve had the opportunity to travel around the world for your research, often in search of fossils and populations living so-called ‘ancient’ lifestyles. What’s your favorite place you’ve been to, and why?
DEL: I’ve been very lucky to have traveled to a lot of really amazing places to see how people use their bodies and live their lives in different cultures and environments. I don’t have a favorite place, but I will say that one of the most thrilling times in my life was when I spent some time just south of the equator with some hunter-gatherers, came back to Cambridge, and then, just a month later, I went on a trip with some Inuit hunters in Northern Greenland, hunting musk oxen. I wasn’t hunting — they were hunting. I was accompanying them on sled dogs in minus 30. So I went from hunter gatherers in Africa, in the hot tropics — almost overnight — to 74 degrees north of the equator, in ice and snow. The contrast was just thrilling.
FM: This semester, you’re teaching Human Evolution and Human Health, part of the college’s Gen Ed program. What would students outside of biology concentrations find compelling about the ideas brought in the course?
DEL: Health is important, and we, right now, are facing a growing health crisis of obesity and all kinds of diseases that are related and associated with obesity. All kinds of chronic non-infectious diseases are on the rise, like Type 2 Diabetes, Alzheimer’s, heart disease, and various kinds of cancer.
We spend such an enormous amount of time and money in our culture today treating those diseases, but we don’t think that much about how to prevent them. To prevent them requires an evolutionary perspective, because these are novel diseases that until recently used to be much more rare. Understanding why we are vulnerable to these diseases provides really important clues to how to prevent them and, in some cases, treat them.
FM: On the topic of chronic disease prevention, one concept you talk about in your work is the active grandparent hypothesis. Can you explain what the theory entails and how you've seen it practiced in your own family?
DEL: The active grandparent hypothesis is the idea that humans evolved to live to be grandparents. We're one of the few species that does that. If you look in human evolutionary history, as humans age, we didn’t become less active, we actually stayed very active. Hunter-gatherer grandparents spend hours every day hunting, gathering, getting food for their children and their grandchildren, doing all kinds of tasks that involve physical activity. There was no retirement, there were no weekends, there were no holidays. That’s what people did every day, for their whole lives, until they died.
I was lucky that my parents were pretty physically active. They weren’t into sports, but they loved hiking and cross-country skiing. We spent summers hiking in various places. I grew up thinking it was normal to be physically active.
My mother also was a pioneer in the women’s running movement. She started running when she was a junior faculty at the University of Connecticut to liberate the women’s gym. She was a lifelong runner and it kept her healthy. She kept doing it. She’s not a spring chicken anymore but every day she trudges on her treadmill and stays active, and it’s really helped her. She's been a good role model for how being an active grandparent really does help keep you young.
FM: Is that a marathon jacket behind you?
DEL: Yes, I’ve actually run, I believe, 26 marathons. So yes, I enjoy running.
FM: What's the best running route in Cambridge?
DEL: I’ve been running the Charles River ever since I was a freshman. I will never get bored running along the Charles. But you gotta do some hills occasionally — Charles is flat — so I also like to run up from Cambridge. Often, I go down to Newton to run Heartbreak Hill, or sometimes I go to Medford or Somerville. Boston and Cambridge are great places to run.
FM: You emphasize exercise and living like our ancestors, but often, research in the field of aging and longevity can get tied to compounds like human growth hormone, testosterone, vitamins and metformin. Why does the innocent quest for a long and healthy life so easily get ensnared by pill-peddlers and quacks?
DEL: As long as people have been trying to prolong their life, there have been quacks. Quackery has evolved along with science. Now instead of selling snake oil, we sell all kinds of pharmaceuticals, pills and high tech stuff, often with the promise that they’ll help extend people’s life, but often with very little evidence.
Today, so much of our medical system, including efforts to prolong life, are about treating symptoms rather than preventing problems from happening in the first place. We pay insufficient attention to prevention, and prevention is really about how you live your life, how you use your body, what you eat, how you exercise, how you deal with stress. Those are never going to be solved by taking a pill.
FM: You’re a prolific researcher, but you’re also a prolific writer. You’ve published several books highlighting progress in the field as well as your own discoveries. Why is writing for general audiences something that’s exciting for you?
DEL: One of the privileges of being a professor at Harvard is that not only do we have amazing students, fantastic colleagues (this is a great place to do research), but also it provides professors with an opportunity to speak to a larger, wider audience. The ideas that we’re working on aren’t just for other academics. What my research is about, really, is how and why we evolved to be physically active and how physical activity is important for health. The best way for me to get that message out to the wider public is not simply to rely on journalists but also to try and be my own voice. I like academic writing, I like writing papers for Science, Nature, and PNAS, but I also love using my own voice in the way that you can in a tradebook, which you can’t do in a scientific paper.
FM: In 2009, you were awarded the Ig Nobel Prize in Physics, which is a parody of the Nobel Prizes, for your paper titled “Fetal Load and the Evolution of Lumbar Lordosis in Bipedal Hominins” published in Nature. The prize purports to honor research that first makes you laugh, and then makes you think. Your research was picked up by the prize committee for analytically determining why pregnant women don’t just tip over. What was your initial reaction when you heard you were selected for the prize?
DEL: I was delighted because I got to have my cake and eat it too. It was a very serious paper in Nature, but also it was publicized by some newspapers as why pregnant women don’t topple over, which I thought was very funny. And I guess that that caught the attention of the Ig Nobel prize committee, and I was very honored to accept it.
FM: Do you think that humor has a role in popularizing scientific discoveries?
DEL: I think humor relaxes people. It helps people recognize that not everything has to be serious all the time, but even things that are unserious can still have serious implications. Humor is an underused rhetorical device in the scientific world.
FM: Barefoot-running enthusiasts and sports medicine clinicians have picked up on your research. You published a paper reporting that barefoot runners strike the ground first with the ball or flat of the foot generating less collisional force than rear foot or heel strikes typical of runners wearing sneakers. Can you tell me about the implications of the research on running injuries?
DEL: People are still arguing about this. I have run barefoot a lot, but I mostly run in shoes. There’s nothing wrong with shoes, but there’s a lot we can learn about running by studying barefoot-running. The key thing about barefoot-running is that if you’re not wearing a shoe, you can’t just slam into the ground really hard, you have to run lightly and gently. I think every runner can benefit from running lightly and gently — that’s the probably the most important message behind that paper.
FM: What do you look for in sneakers as a result of this work?
DEL: I hate having sneakers that have a lot of stuff in them. I like minimal shoes and minimal sneakers. So I look for sneakers that have a nice wide toe box. I don't like arch support, very stiff soles and lots of cushioning. I want something just to protect my foot, and I want to use my foot in a way that’s something more along the way in which my foot evolved to be used rather than the way big shoe companies want to manipulate it.
FM: Did the research inspire your barefoot running, or was it vice versa?
DEL: The barefoot running started because I had been doing some research in Kenya. We were looking at people who had never worn shoes. I got back from the trip, a long flight back from Kenya. I remember it was a summer morning, really early in the morning. I was thinking about it and I was running in the streets of Cambridge. I just took my shoes off and ran about a half-mile home barefoot. I loved it. It felt good. So I started doing more of it. It became like a feedback loop: the more we’re studying barefoot running, the more I got interested in trying it myself — I believe in trying what you study. The more I did it myself, that gave me insights into the kind of research questions that we were working on.
When you wear a shoe you get protection but you lose sensory perception. I had the sense that running barefoot with a thick callus, I had protection without losing sensory perception. And so we actually ended up studying that: we looked at the thickness of people’s calluses in Kenya and the United States and measured their sensory perception using all kinds of fun techniques and published a paper in Nature showing that you know how calluses work to protect the foot while not compromising your ability to sense the ground underneath you. Think about it: for all animals, the foot is their only contact with the ground. It’s very useful to get information from what’s happening between your foot and the ground.
FM: If you could take away one invention that makes modern life easier from Harvard’s campus, what would it be and why?
DEL: We have too many elevators on campus. When I was a student, you had to have a key to use the elevators. Of course, sometimes people need to use elevators if they’re disabled or they have an injury. But it’s good for people to climb the stairs up to the fifth floor of the Peabody Museum instead of taking the elevator. We would all be better off if more people took the stairs.
— Associate Magazine Editor Dina R. Zeldin can be reached at dina.zeldin@thecrimson.com.
