Exercised by Daniel Lieberman

Modern industrial people are in the unique predicament of having lifestyles that are so physically undemanding that their inactivity is causing negative health effects. Physical exercise is often prescribed as a way to restore a natural balance, but people experience difficulty both in finding the willpower for it and in deciding what sorts of exercise to do. Discussions about health and fitness frequently get sidetracked into discussions about what is “natural” and “normal” for humans. We can help resolve such questions by learning about the lifestyles of hunter gatherer people and comparing humans with their most similar ape relatives.

Are humans naturally lazy? Yes. All animals are naturally lazy. Animals rationally try to expend as little energy as possible, which means avoiding any exertion that’s not necessary for survival or reproduction. Hunter gatherer humans sometimes exert themselves unnecessarily (eg play, dancing) but there is always a useful training-related or social element to these activities. The idea of exerting oneself unnecessarily purely for health maintenance is a new idea that does not exist outside of industrialized human populations. Exercise is inherently unnatural and runs against deep-rooted instincts that call for energy conservation. It is therefore normal to lack intrinsic motivation for it.

Are humans naturally sedentary? Yes. Excessive sitting has often been blamed on modern-day health problems. However, while pre-industrial people are more active than industrial people, they only spend a slightly smaller fraction of their day being sedentary. Hunter gatherer sitting sessions tend to be brief, tend to contain movement, and tend to be on uncomfortable unsupported surfaces that force them to work their muscles. The modern style of sitting - slouching motionless on comfortable high-backed chairs for very long time periods - is a very recent development. How much time people spend being sedentary appears to be less important than how the time is spent.

Are humans naturally fast? No. Thanks largely to their bipedal walking pattern, humans are significantly slower sprinters than most four-legged animals, including even small animals like squirrels. Hunter gatherer humans cannot outsprint their prey or predators, instead relying on group protection, ranged weapons, and animals’ natural fear of fire. Humans can only do all-out sprints for about 30 seconds before their short-term energy stores run out and they must switch to slower but more sustainable metabolic processes.

Are humans naturally strong? No. The trope of the muscular caveman is inaccurate; hunter gatherer and agrarian people are lean rather than bulky. Humans are less muscular than other ape species and Homo sapiens is likewise less muscular than some of the other human species before it. As humans increasingly relied on tools rather than brawn, physical strength became less important over time throughout human evolutionary history. For pre-industrial people, excessive muscle mass merely increases the body’s energy expenditures without much compensation. Bulky bodybuilder-like physiques require exercise equipment and a lifestyle that is only accessible to industrialized people.

Are humans natural walkers? Yes. Hunter gatherers regularly walk 10-15km every day, often while also carrying heavy loads. The human bipedal walking pattern is very energy-efficient, much more so than the four-limbed gait of other apes. Historically, one of humans’ greatest evolutionary strengths compared to other animals was their ability to travel great distances in the course of a day. Increased walking is frequently prescribed today as a weight loss technique. However, since human walking is so energy-efficient, the weight loss effects of walking are slow and modest.

Are humans natural runners? Yes. Humans are poor sprinters by animal standards but they are very good long-distance runners. Humans have many adaptations for running and for endurance, including long legs, springy tendons, stabilizing muscles, elastic heart chambers, abundant sweat glands, and a lack of fur. Hunter gatherer humans use their endurance to outrace other scavengers to distant animal carcasses and to chase prey animals to the point of exhaustion. Hunter gatherers run with short stride lengths and land on the balls of their feet rather than the heels; this technique is less stressful for the knees.

Are humans naturally inactive in old age? No. Hunter gatherers have no concept of retirement and remain active for their entire lives. Hunter gatherer grandparents generally perform the same activities that younger adults do without cutting themselves slack. In contrast, modern industrialized people significantly reduce their physical activity with age. Thanks to their continued high physical activity, the physical capabilities of hunter gatherers deteriorate more slowly with age than those of industrial people. Whereas industrialized people tend to die slowly from long-term chronic diseases, hunter gatherers remain able-bodied for their entire lives and die fast deaths from infections or injuries.

Humans evolved to fit into an ecological niche in which physical activity was common and unavoidable. The human body is designed to be in motion and is not adapted to idleness. In modern times, a lack of activity is associated with poor health, rapid aging, and the development of various chronic diseases. In contrast, hunter gatherers who avoid early death are able to live to an old age without ever experiencing the long-term illnesses typical of modern times.

Why is physical activity so important for health maintenance? In the very short term, physical exertion is undenyingly negative: muscles and bones experience physical damage and the body gets flooded with harmful waste chemicals. However, this damage triggers a flurry of repair mechanisms to fix it; these processes often overcorrect and build the body back stronger than before. To help conserve energy, these expensive repair processes are triggered only in response to significant exertion and not in response to baseline metabolism. This particular quirk of the human body wasn’t significant when all people had to be active by necessity, but it is very significant today. People who live inactive lives still accumulate natural wear and tear, but the usual repair processes don’t kick in to fix the damage. Inactive lifestyles therefore lead to a slow accumulation of tissue damage, long-term low-grade inflammation throughout the body, and accelerated aging.

For modern industrialized people, exercise is essential. According to most health authorities, people should aim for at least 150 minutes of activity per week that is of moderate intensity or higher. Even a small amount of exercise is much better than none; the benefits continue growing with increased time, though with diminishing returns. For overall health and fitness, it appears to be best to have a variety of activities (eg cardio, weights) at a variety of intensity levels, including occasional bursts of very high intensity. Exercise doesn’t improve health as abruptly or decisively as quitting smoking or making diet changes, but exercise is good at preventing long-term health problems and at keeping lost weight from returning.

Exercise may be essential, but it still unnatural and costs lots of willpower. People face less internal psychological resistance to physical activity if it is a necessary element of their baseline lifestyle, if it is inherently enjoyable, or if there is a social element involved. Making physical activity more social creates a sense of togetherness and accountability; it appears to be the most realistic way of getting people started with exercise routines. Exercise routines are difficult to establish but pay dividends once they are become a habit. Habitual exercisers often find they don’t feel at their best when they go too long without exercising, thereby giving them the motivation to return. Inactivity is a vicious cycle of internal resistance, but high physical activity is a virtuous cycle of improving health and improving motivation.