Today, most of us tend to medicalize exercise, turning it into something that we “have” to do. Case in point: the treadmill. If our main goal was enjoyment, there’s no way we would regularly spend 45 minutes walking in place on these expensive machines.

But our relationship with exercise — or, more generally, physical activity — was not always so discrete and joyless. For much of human history, people got plenty of physical activity not only by walking long distances, but also by doing activities that were both necessary and socially rewarding, like hunting, dancing, and sports.

Harvard biologist Daniel Lieberman argues it’s time to rethink our relationship with exercise, and to understand physical activity as a complex and integral part of human evolution. After all, while walking thousands of steps through the environment to find our next meal was a major part of our evolution, walking on the treadmill was not.

DANIEL LIEBERMAN: Treadmills are really weird. They're a strange, modern piece of equipment that we spend a lot of money on, and we spend a lot of money to go to a gym- that makes you work really hard to stay in the same place. 'It's the apotheosis of exercise.' Think about it a treadmill, right? We think treadmills are synonymous with exercise, but it's a noisy, expensive machine that makes you work really, really hard for no purpose other than to make you move without getting anywhere. Most of us, if we're forced to be on a treadmill, we listen to a podcast or some music, we watch something on our iPhones or whatever to make it tolerable. My name is Dan Lieberman. I'm a Professor of Human Evolutionary Biology at Harvard University, and I'm the author of "Exercised," why something we never evolved to do is healthy and rewarding. 

The very first treadmills were probably invented by the Romans or even some other ancient peoples like that to move wheels and stuff like that. But the modern treadmill's real genesis comes from Victorian prisons. They were invented by a man named William Cubitt at some point in the 19th century to prevent prisoners in England, like debtors' prisons, from relaxing and enjoying themselves. So they would make prisoners sort of trudge for hours a day on these big slat-like treadmills to make it unpleasant for them to be in jail. And of course now, people still trudge on treadmills, except they do it on their own volition, but many of them still feel like it's a kind of form of torture. I don't know anybody who really enjoys being on a treadmill.

OLD TELEVISION SEGMENT: 'It's easy to squeeze your way to shapely hips and thighs.'

LIEBERMAN: So many modern forms of exercise are kind of like cod liver oil-they're not really pleasant.

OLD TELEVISION SEGMENT: 'Extra sunshine for us in winter and spring.'

LIEBERMAN: We do them because they're good for us.

OLD TELEVISION SEGMENT: 'Come on, go, go!'

LIEBERMAN: But it's not fun.

OLD TELEVISION SEGMENT: 'Make your muscles cry.'

LIEBERMAN: And so it's like taking your medicine. It's important to make a distinction between physical activity and exercise- so physical activity's just moving. You do anything: go shop, pick up your groceries and take them to your car, that's physical activity. When you sweep the kitchen floor, that's physical activity. But exercise is discretionary, voluntary physical activity for the sake of health and fitness. 

The word exercise comes from the Latin 'exercitatio,' and it meant "to train." We still do math exercises. When you were plowing a field, for example, that would be considered exercise in sort of early English. Or soldiers do exercises to get fit. On the other hand, it also means to be exercised, to be upset, to be confused, to be anxious, to be kind of worried. You know, we get exercised by our math exercises. In the modern world, a lot of people are confused about exercise. They find it hard to do, they're not quite sure how much to do, there are all kinds of myths surrounding it.

OLD TELEVISION SEGMENT: 'The burning is a signal that your muscles are working harder than they should.'

LIEBERMAN: Most people don't do it because they want to, they do it because it helps to stave off death and decrepitude. By shining the light of evolution and using kind of an anthropological perspective, my goal really is to help people be less exercised about exercise.

OLD TELEVISION SEGMENT: 'Right, left, right, left. Walking is one of the great exercises for people of all ages.'

LIEBERMAN: If there's any one physical activity that humans evolved to do, it's to walk. Walking is the way which humans get around, get food. It's kind of fundamental to who are as a species. Today, in the modern Western world, with cars and escalators and elevators and Zoom and TV and all that sort of stuff- we just don't walk very much. You know, the average hunter-gatherer will take maybe 10-15,000 steps a day. The average American, before the pandemic, was taking something like 4,700 and something steps a day. So a lot less than our ancestors. 

One of the ways which we medicalize exercise in the Western world is that we think there's a certain amount you should do, right? We prescribe it. "You should take two aspirin, you should get eight hours of sleep, and you should walk 10,000 steps a day." We like that, right? There's nothing necessarily wrong with a goal, right? Goals can be really helpful, actually. But 10,000 steps is kind of arbitrary. The number actually came from when the first pedometer was invented in Japan before the 1960s Olympics. In the board room, they were trying to decide what to call it. It turns out that 10,000 is a very auspicious number in Japan, and they thought it kind of sounded good, it seemed kind of reasonable, so they called it 10,000-step monitor- and that kind of stuck. Surprisingly, it turns out that 10,000 steps isn't actually a bad goal. If you actually look at what people in non-Western societies do, 10,000 steps isn't actually that far off. So, it's a perfectly reasonable goal to shoot for, but there's nothing, like, special about it. If you do 8,000 steps, that's fine; if you do 15,000 steps, that's fine. The important thing is to be physically active because some is better than none, and a little bit more tends to be better than that. But you know, it's all good. There's no magical number. It's not a U-shaped curve with a bottom on it, right, where it tells you what you should aim for. That does not exist. 

I mean, every culture engages in sports, right? It's a human universal. Sports are important. They serve all kinds of functions. There's a lot of wonderful things about being on a team and especially when you're children, you learn good sportsmanship. If somebody scores a goal on you, it's not appropriate to bash them in the face, that sort of thing. You learn hierarchies, you learn companionship, you learn how to cooperate. But some sports also have another origin. It's not coincidental that a lot of the sports, for example, in the ancient Olympics, especially, were skills that were really important for warriors. You know, javelin throwing and chariot racing. Well, we don't do chariot racing anymore. Sprinting, wrestling, boxing, right? These are all very kind of physically demanding sports that are kind of combat-related. Sports, I think, evolved also to help us learn not to be 'reactively aggressive'- sort of like an instant kind of non-planned aggression. I mean, the extreme to me is tennis.

ANGRY TENNIS PLAYER: 'You cannot be serious!'

LIEBERMAN: You're not even allowed to swear when you're playing tennis.

ANGRY TENNIS PLAYER: 'We're not gonna have a point taken away because this guy is an incompetent fool. You know that? That's what he is.'

LIEBERMAN: Road rage is a perfect example of reactive aggression.

MIDNIGHT COWBOY MOVIE LINE: 'I'm walking here, I'm walking here. Up yours, you screwball!'

LIEBERMAN: But there's also 'proactive aggression,' when you plan something, premeditate, you work it out in advance. War is an example of a proactive aggression. Sports are also kind of proactive aggressions sometimes. It's perfectly acceptable to appropriately proactively aggressive, as long as you're within the rules. And that's what humans excel at. We're better than most species at curbing reactive aggression, though not so often, but we are capable of extraordinary proactive aggression. You know, every once in a while there's a mass shooting, and there's a kind of standard reaction. Everyone says, "Oh my gosh, how could this person do this? I go to church with him, and whatever. Just a nice person, etc." But we're confusing reactive aggression with proactive aggression. Hitler was a vegetarian, but of course one of the most proactively aggressive human beings who's ever lived. 

We shouldn't confuse these two different kinds of aggression. Our bodies weren't designed, they weren't engineered, they're not machines- they evolved. And so if you want to understand why our brains work the way they do, why our feet work the way they do, why we run, why our immune systems function the way they do, the only explanation for those types of questions is an evolutionary question. There's an old expression: "Nothing in biology makes sense except in the light of evolution." I would say that nothing about human behavior makes sense except in the light of culture and anthropology, and we need to understand the cultural component to our behaviors as well.