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.

- 'It's easy to squeeze your way

to shapely hips and thighs.'

- So many modern forms of exercise are kind of like

cod liver oil-they're not really pleasant.

- 'Extra sunshine for us in winter and spring.'

- We do them because they're good for us.

- 'Come on, go, go!'

- But it's not fun.

- 'Make your muscles cry.'

- 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.

- 'The burning is a signal that your muscles

are working harder than they should.'

- 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.

- 'Right, left, right, left.

Walking is one of the great exercises

for people of all ages.'

- 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.

- 'You cannot be serious!'

- You're not even allowed to swear

when you're playing tennis.

- 'We're not gonna have a point taken away

because this guy is an incompetent fool.

You know that?

That's what he is.'

- Road rage is a perfect example of reactive aggression.

- 'I'm walking here, I'm walking here.

Up yours, you screwball!'

- 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.