What Evolutionary Biology Teaches Us About Diet, Exercise, and Life

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What can the science of ancient humans and the lifestyle of hunter-gatherers teach us about how to be healthy today? Harvard evolutionary biologist Daniel Lieberman joins the show to talk about his provocative “mismatch theory,” why humans are dysevolved for the modern world, and why exercise is the ultimate miracle drug.

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In the following excerpt, Derek and Daniel Lieberman discuss the mismatch hypothesis and why the paleo fetish is so flawed.

Derek Thompson: Dan Lieberman, welcome to the show.

Daniel Lieberman: Thank you. I’m delighted to be here.

Thompson: You are a professor of human evolutionary biology at Harvard University. What is human evolutionary biology?

Lieberman: I and others in my department study how and why humans evolved to be the way we are, and we’re also generally interested in the question of how that evolutionary story is relevant to the challenges that human beings face today.

Thompson: For someone in 2024 trying to ascertain answers to extremely modern questions like “Should I eat the Flamin’ Hot Cheetos in front of me?,” “What time should I go to bed tonight?,” what use is this domain, with your long telescope lens? Why should we care about human evolutionary biology to solve extremely 2024 problems?

Lieberman: I think a simple way to answer that is that we weren’t designed; we weren’t engineered. We evolved. And if you want to understand how and why we are the way we are, you have to know something about that evolutionary history. And it’s not like a blueprint. I think one of the frustrating ways in which I think some people use evolutionary data and theory to think about how to live their lives is to think, well, if hunter-gatherers do it, I should do it, too. That’s a very facile answer, but there is much to learn about how we use our bodies and how our minds work and how we behave from studying that evolutionary history. And that can help us evaluate the costs and benefits of different ways to live one’s life.

Thompson: I’m very glad that you called the paleo fetish facile because it drives me completely crazy. I am both very interested in your work and what our evolution teaches us about the bodies that we arrived into this world with, but at the same time, when people hold up the sort of paleo experience or the Cro-Magnon experience, the Homo erectus, whatever experience, as being this North Star that we have to aim for, I always think, let’s remember the moral code of those ancient civilizations. They were very different from us in many, many ways. We don’t have to go back 20,000 years just to find health and happiness and flourishing in the 2020s.

Lieberman: No, but if I can just interrupt you, we did evolve. Agriculture was invented only 600 generations ago. That’s the number of generations of mice that have probably lived in my basement since this house was built. It’s been a blink of an eye that we’ve been living, eating farm food. In fact, the industrial revolution was just a few generations ago. In fact, it’s still ongoing in some parts of the world. We can learn a lot about what kind of bodies we have and what kind of minds we have if I’m studying evolutionary history. But it’s important to remember that probably the most important flaw with the kind of paleo thinking, the paleo fantasy it’s sometimes called, is that we didn’t evolve to be happy, to be healthy, to be nice. We only evolved to have as many babies as possible who could survive and reproduce. So we evolved to be healthy only to the extent that health improves our reproductive success.

So just because our ancestors did something doesn’t mean that’s optimal for us. In fact, I hate the word “optimal.” It just simply means our ancestors did it and that there’s some information that we can learn from that. But of course, there are lots of things in the modern world that our ancestors didn’t have, which I’m sure they would’ve loved to have, like, I don’t know, sterile surgery, refrigerators, freezers, et cetera. But there are also things today that cause all kinds of troubles, and we call those mismatch diseases. And evolutionary history helps us evaluate them.

Thompson: When we’re studying our ancestors from seven generations ago, how do we know what we know?

Lieberman: Well, we have to piece it together from various forms of evidence. I mean, we do have ethnographic evidence from hunter-gatherer populations that live around the world. There are still a few, not many, and they’re not entirely hunter-gatherers, but we can still learn a lot from them. We also have a really amazing archaeological record, which is filled with clues and information about how our ancestors used to live. We know what they ate, to a large extent. So we can put together a reasonably comprehensive picture about many aspects of our ancestors’ lives.

Thompson: I was really drawn to your work initially because it provides an incredibly useful framework for thinking about what’s become a major theme of my writing for The Atlantic and also of this podcast, which is something like the costs of modernity, or maybe the ironic downsides of progress. We do episodes about why young people are so sad, why Americans are so anxious, why aloneness has increased in America, and why this is all happening at a time when, by many accounts, you might expect that the opposite would be true.

We have more ways to be entertained, more ways to connect, more ways to be with other people. And into this confusion or into this conundrum, you’ve presented two books, The Story of the Human Body and Exercised, that together hold up this really big idea, this very important or stable frame that I think brings a lot to the picture, which is something you call the mismatch hypothesis. You’ve already alluded to it in the last few minutes. I want to talk about this idea before we dive into the more somewhat self-health-y parts of the conversation, which is the lessons of anthropology for diet and exercise and wellness. But let’s start by getting this framework set. Could you please help us define the mismatch hypothesis?

Lieberman: Sure. All organisms are adapted to a particular environment. Think about a zebra out there on the savanna eating grass. It’s adapted to that particular environment. And evolution often occurs when the environment changes around animals. If you take a zebra and you put it in the Arctic, that zebra is going to struggle, be mismatched to that environment. We’ve also changed our environments recently. There’s all kinds of reasons for environmental change, but one of the biggest causes of environmental change is culture. We’ve evolved all kinds of new foods to eat. We’ve created new technologies like shoes and chairs and elevators and shopping carts and television and iPhones, and the list goes on. Sometimes those things bring benefits, or in many ways they bring benefits, but in some ways they are what we call mismatches. So mismatches are when you are inadequately or imperfectly adapted to a novel environmental condition, and that’s the essence of a mismatch.

That zebra in the Arctic is clearly mismatched to its novel environmental condition. In some ways, we are mismatched to, say, eating too much sugar. I don’t think that’s a very controversial statement. Or mismatched to, I don’t know, McDonald’s or, I don’t know, lawyers. There’s many kinds of mismatches out there, and they’re complex because most of them are environmental changes that bring some benefits, but they also, at the same time, bring some costs. The costs in terms of health, we call them mismatch conditions. I’ll give you a trivial one. We evolved to eat all kinds of food, but we never evolved to eat a lot of food with a lot of starch and sugar. When we do that, the bacteria on our teeth go crazy, and if they get caught on our plaque as they digest those sugars, they produce a lot of acid, which causes cavities, and so we get cavities.

We’re basically mismatched to eating a high-sugar, high-starch diet, so we have to go to the dentist to have our cavities filled, and we have to brush our teeth and all that kind of stuff. Other mismatches, of course, are much more serious. We’re mismatched to the same high-sugar diet. It can cause diabetes, type 2 diabetes, for example. Or a wide range of dietary issues can cause obesity, which can cause some health concerns. So there’s lots and lots of mismatches that occur basically, again, from our bodies being imperfectly or inadequately adapted to novel conditions.

This excerpt was edited for clarity. Listen to the rest of the episode here and follow the Plain English feed on Spotify.

Host: Derek Thompson
Guest: Daniel Lieberman
Producer: Devon Renaldo

Subscribe: Spotify



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