“Exercise more” is probably on the to-do list of every person you know. And it’s no wonder – getting active is touted as a remedy for obesity, mental illness, lethargy, and a long list of physical ailments.
All of this advice is well-meaning, but sometimes it can be confusing. We know running is healthy – but doesn’t it also damage your knees? We know we should sleep for eight hours – so why do many of us wake after seven?
These sections cut through the noise by approaching things from two directions: the history of humans’ evolutionary past, and present-day groundbreaking research. The results combine the ancient and the modern in a fresh and invigorating vision of human health.
We didn’t evolve to exercise
When you imagine our early human ancestors, you probably envision them in motion. Whether they’re hunting animals, navigating harsh landscapes, or even fighting, it’s likely you imagine them as active rather than sedentary – and on the whole, that’s fairly accurate.
For our predecessors, physical activity was an unavoidable part of life. Whereas we can just stop at a supermarket to buy more food, early humans didn’t have that option; if they wanted to eat, they had to get moving.
So what does that tell us about exercise, then? That it’s something evolution compels us to do? That it’s entirely natural? The short answer is no.
On the face of it, this is a shocking idea – if we evolved to be physically active, then surely we evolved to exercise. What’s the difference?
The crux of the issue is that exercise is voluntary physical activity, usually undertaken in order to improve our health and fitness. Humans evolved to be active when circumstances demand it – like when food is running low and our bellies start to rumble. With a few exceptions like dancing and childhood games, we didn’t evolve to engage in unnecessary activity.
In short, evolution hasn’t actually given us any impulse to exercise; on the contrary, forcing ourselves to get moving involves overcoming some of our most basic instincts. So if it seems hard to make yourself go on that jog, rest assured – that’s just as nature intended.
Our aversion to unnecessary activity actually makes a lot of sense. Moving around requires energy, and for energy we require food. For us, that doesn’t seem like a big deal; one soda contains all the energy you’re likely to burn on a 90-minute walk. Replenishment is no big deal.
But until very recently – evolutionarily speaking – circumstances were different. Food was hard to come by, which meant that wasting energy was dangerous. Any unnecessary activity you engaged in would deplete your reserves – leaving you with less energy to devote to the vital tasks of surviving and reproducing.
So does all this mean we should give up on exercising? No – quite the opposite! By explaining why keeping fit can feel like such a slog, this insight can help us to adopt a more understanding attitude toward ourselves and others.
In a nutshell, we shouldn’t shame people for their reluctance to exercise; we should realize that overcoming our instincts takes work and dedication.
We don’t all need eight hours’ sleep
It seems we have a crisis. Experts are ringing alarm bells: All over the industrialized world, there is a shortage of sleep.
In days gone by, the experts say, people used to sleep for up to ten hours a night. Today, the average Westerner gets just seven – a whole hour less than the recommended eight. And what’s worse, five percent of us get less than five hours’ sleep each night!
According to the experts, the effects of this “epidemic” are terrible. Sleep deprivation promotes obesity, causes car crashes, and affects our performance at work – it saps every aspect of our lives.
That’s the common refrain, at least – but the facts demand investigation. Are we all really sleeping too little, or is there more to this question than meets the eye?
The idea that we need to sleep for eight hours a night has murky origins. No one’s quite sure how it emerged, but what we do know for sure is that, in the nineteenth century, striking factory workers liked to shout, “Eight hours for work, eight hours for rest, eight hours for what we will!” As a slogan, it’s memorable. But it’s on rockier ground as sleep advice.
In recent years, our understanding of sleep has been revolutionized by some groundbreaking research – much of which was carried out by the sleep researcher Jerome Siegel and his colleagues at UCLA.
Siegel and his team investigated the sleeping habits of hunter-gatherer and hunter-farmer groups in Tanzania, the Amazon rainforest and the Kalahari desert. Contrary to popular belief, they found that these populations slept not more, but less, than those living in the industrialized world. On average, they got about six and a half hours’ sleep each night – with a little less in summer and a little more in the winter months.
Research into Amish farmers, rural Haitians, and subsistence farmers in Madagascar arrived at similar results. The unavoidable conclusion? It’s perfectly normal to get less than eight hours’ sleep. In fact, studies indicate that people who get seven hours’ sleep tend to live longer than those who sleep either more or less.
So don’t worry if your sleeping pattern doesn’t exactly match the experts’ recommendations. And if you do find yourself feeling sleep-deprived, remember that one of the best recipes for a good night’s sleep is a daytime bout of exercise.
We didn’t evolve to be naturally brawny
So our caveman and cavewoman ancestors probably didn’t sleep for eight hours a night. They also didn’t go on spontaneous and unnecessary jogs. But if there’s one thing we do know about our hunter-gatherer ancestors, it’s that they must have been extremely strong.
That’s according to primal fitness enthusiasts, anyway. Proponents of this theory believe that our ancestors’ everyday activities would have kept them fit, muscular, and lean; hunting animals would have tested their stamina, for example, and moving boulders would have required mammoth strength.
In this view, our modern, sedentary lifestyles have turned us into weaklings – so it’s up to us to regain the strong and chiseled bodies that evolution gave us.
But is this accurate?
Once again, there’s a slight problem with this image of preindustrial humankind: it’s totally at odds with what is seen in hunter-gatherer populations today.
Take the Hadza, a hunter-gatherer people from Tanzania. Measurements show that they’re lean and moderately strong, but they’re generally not burly. Tests of Hadza grip strength and estimates of their overall upper-body strength fall squarely within Western norms – and actually fall below those of athletes.
The same is true for other hunter-gatherer peoples, such as the Mbuti of central Africa, the Batek of Malaysia, and the Aché of Paraguay. They’re fitter than most Westerners, for sure – but their strength and muscle size are nothing to marvel at.
One reason for this is that it’s simply hard to build muscle without gym equipment. Body-weight training, – that is, exercise where you only use your own body’s weight as resistance – can help you get fit, but unless you get heavier, the weight you lift remains the same. Over time, this makes increasing your strength a challenge.
From an evolutionary perspective, there’s a more fundamental reason why we’re not all hulking Goliaths: maintaining muscle requires a lot of calories. On average, about one-fifth of our energy intake goes to muscular upkeep – but if we increase our muscle mass, we increase that figure.
Sure, being beefy has its benefits – it might help you kill an angry predator or attract a mate. But these benefits weren’t significant enough to outweigh the costs of maintaining added muscle. In short, we evolved to be strong enough to cope with everyday challenges – not to look like Arnold Schwarzenegger.
Walking does have a role to play in weight loss
Exercise scientists are generally a peaceful bunch. But one question can have even the most placid researchers clawing at each other’s throats: Can you lose weight by walking?
Until recently, it seemed clear-cut. Moderate exercise, like walking, requires energy – and when your energy output exceeds your energy intake, you burn fat. Right?
Well, according to the opposing camp, it’s not that walking has no effect – it’s just that it’s a fairly laborious way to shed a few pounds. But are they right? Should we drop walking from our weight-loss regimen?
The main points against walking for weight loss are that it burns very few calories, and ultimately makes people hungry – meaning that walkers often compensate for their activity levels by eating more.
This pessimistic view is borne out by a large body of research. In one study, a group of overweight and unfit men and women were instructed to walk briskly for 150 minutes a week, without modifying their diets. The results? Almost no weight loss, unfortunately.
The reason for this is that we humans have evolved to be wonderfully efficient walkers. Walking is just one of the things that we’ve developed to do easily and well. In most situations, that’s a blessing – but it can make it hard to lose weight.
Luckily, there’s some hope. That same study also observed a group that walked twice as much, for 300 minutes a week. Their results were more encouraging. After twelve weeks, they’d lost an average of six pounds. It’s not huge – but sustained for a year, that could be 26 pounds off the scales.
So it seems that in order for walking to lead to weight loss, we need to do lots of it. But more important than walking’s initial role in shedding pounds is the part it plays in helping us to maintain a healthy weight.
Within a year of a crash diet, people who avoid exercise regain, on average, half the weight they’d lost – and after that, they slowly return to their starting weight, bit by bit. But for people who shed weight and regularly exercise it’s a different story: they’re far more likely to maintain the weight they worked so hard for.
Walking’s not a miracle pill, then. But the role it can play in weight loss and weight maintenance shouldn’t be overlooked.
Running doesn’t have to lead to injuries
So, we’ve learned that walking can be useful. It can help you to lose weight and stay slim – and it doesn’t require very high levels of fitness. But what if you’re interested in something a little more challenging – something to get your heart racing and your legs pumping? What, in other words, about running?
For novices, running can be daunting. Many would-be runners are put off for life by the horror stories of veterans – people complaining of wear and tear to muscles and joints, and all kinds of exotic injuries.
Are these people exaggerating? Is running really that damaging?
Runners do sometimes pick up injuries – that much is obvious. But they’re not actually as common as you might think. Evidence suggests that running injury rates follow a U-shaped curve. Novices and very serious runners are the most likely to be injured, whereas the moderate runners between those two extremes have relatively few issues.
This surprises some people, especially those who think that running can cause osteoarthritis. Doesn’t pounding the pavement day after day wear down your cartilage over time? Actually, no – on the contrary, studies show that running and other forms of physical activity help promote healthy cartilage.
That isn’t to say that running never leads to injury. It sometimes does. So what can we do to minimize that risk?
Put simply, we need to give the body time to adapt. The enthusiasm with which some novices throw themselves into the sport is admirable, but it’s not wise. Increasing your mileage or speed by more than ten percent a week puts you at risk of injury – and there’s nothing your eagerness can do to fix that.
When the body does adapt, though, it can be fascinating to observe – as Daniel E. Lieberman discovered back in 2015. He followed eight runners who ran 3,080 miles across the US. For half a year, they ran about a marathon each day, taking just one day off a week. At the start, they experienced all the pain and stiffness you’d expect – but, bit by bit, they adapted.
Of the fifty injuries the runners reported, about 75 percent occurred in the first month. And in the final month, they reported none at all.
We need to stay active as we age
How do you picture your retirement? Whatever you envision, it’s probably unlike the lives lived by older members of hunter-gatherer societies.
Take the Hadza, the Tanzanian hunter-gatherer people we encountered in an earlier section. While Americans walk half as much in their seventies as they do in their forties, the Hadza’s activity levels go through a much more moderate decline as they age. One result of that is that they stay fit and strong much longer than people living in the industrialized world.
In fact, hunter-gatherers also live quite long lives, despite the fact they’re unfamiliar with modern medicine; those who survive infancy typically live to be between sixty-eight and seventy-eight years old. That’s not far off the life expectancy in the US, which is currently somewhere between seventy-six and eighty-one. So what can we learn from them?
One thing we can learn from older hunter-gatherers is that many so-called “diseases of aging” aren’t actually inevitable as we grow older. Heart disease, type 2 diabetes, and Alzheimer’s rarely appear in hunter-gatherers at all.
So why is that? In short, it’s down to a phenomenon that scientists call compression of morbidity. Whereas in the industrialized world, many of us are plagued by ill health or “morbidity” for decades before we die, hunter-gatherers’ physical decline is compressed toward the end of their lives. Their secret? You probably guessed it – sustained activity into old age.
We can see this play out closer to home too – as James Fries, a celebrated medical professor, showed in the Stanford Runners Study. Observing five hundred amateur runners and four hundred inactive but healthy participants, Fries and his team tracked this group of over-fifties year after year.
What they found was that non-runners died at accelerating rates compared to their active counterparts. By the end of the study, members of the inactive group were about three times more likely to pass away in a given year than the runners were.
What’s more, the runners didn’t just live longer: they lived better, too. The researchers kept track of participants’ ability to carry out basic tasks like walking, dressing, and other routine activities – and they found that non-runners lost these capacities at double the rate of the running group.
The bottom line, whether you live in rural Tanzania or downtown Boston, is that keeping active as you age can help you live longer, stave off illness, and maintain your physical abilities.
If we want to exercise more, we need to make it as fun and necessary as possible
We know exercise is good for us. We know we should exercise more. But now we also know why we so often find it difficult and unpleasant – because we didn’t evolve to engage in voluntary physical activity. From the standpoint of our ancestors and our evolutionary history, exercising is weird.
That’s a fact we have to reckon with; it means that when physical activity is unnecessary or boring, we’ll probably try to avoid it. But rather than being paralyzed by that insight, can we harness it for our own benefit?
Earlier, we characterized exercise as voluntary or unnecessary physical activity. That’s its hallmark, but it’s also a problem: exercise is good for us, but it’s not a total necessity. In other words, we might not thrive if we’re unfit, but odds are that we’ll get by.
Grasping this fact helps to point us toward a solution: If we can’t make exercise an actual necessity, we can at least try to make it more necessary. How? By creating an environment that coerces us into staying fit.
One way of doing this is to ask someone you respect to check your progress and make sure you’re meeting your goals. Alternatively, consider signing up for a race and paying ahead of time. You won’t be compelled to take part, of course, but putting your money on the line will make you think twice about skipping training or dropping out. To put it another way, preparing for the race will seem more necessary once you’ve paid up.
But it’s not enough to coerce yourself into exercising. In the best-case scenario, that’ll leave you fit but more than a little miserable. If you really want to make exercise a part of your life, you’ll also need to make it more fun.
Luckily, there’s one ancient, tried-and-tested method of sweetening physical activity: making it social. In hunter-gatherer societies, men often travel in pairs when they hunt or collect honey. And when the women forage, they go in groups, gossiping and enjoying each other’s company.
So be social. Exercise with friends or a team or a trainer. And if all else fails, there’s always straightforward distraction – a podcast can be incorporated into almost any workout.
The bottom line is that exercise is good for us – and the better we understand our instinct to loll about, the more effectively we can overcome it.
Exercise isn’t easy, because it violates our natural tendency to conserve energy. The solution is to make physical activity seem both necessary and fun – while resting well and making sure not to overtrain.
Instead of endless fussing about what the ideal workout regime would look like, try to adopt a simpler attitude. Research bears out a few straightforward principles: exercise lots – mostly cardio, but also using weights – and keep it up as you get older. You needn’t make your exercise program any more complex than that.
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