The evolution of laziness: Why humans resist the gym | Daniel Lieberman: Full Interview

Key Concepts

Evolutionary biology, anthropology, physical activity vs. exercise, physical activity level (PAL), basal metabolic rate, myths about exercise, sitting is the new smoking, sleep myths, speed vs. endurance, strength vs. power, sarcopenia, reactive vs. proactive aggression, walking, running, knee injuries, medicalization of exercise, inflammation, mental health benefits of exercise, elite athletics, WEIRD societies.

How Evolution Shaped the Human Body

Dan Lieberman, a professor of human evolutionary biology at Harvard University, emphasizes the importance of understanding human biology and behavior through the lens of evolution. He argues that while mechanistic explanations are valuable, evolutionary explanations are crucial for understanding why our bodies function the way they do. He also stresses the importance of incorporating an anthropological perspective to understand the cultural component of human behaviors.

• Evolutionary Perspective: Human bodies evolved, they weren't designed. To understand why our bodies work the way they do, we need to consider evolutionary explanations.
• Anthropological Perspective: Human behavior is also shaped by culture. A complete explanation requires integrating physiology, evolutionary biology, and anthropology.
• Head Stabilization Example: Lieberman's early research focused on how humans stabilize their heads while running. He discovered adaptations that evolved around 2 million years ago specifically for this purpose.
• Kenyan Research: Lieberman's work in Kenya involves studying how bodies change as people transition from rural, subsistence farming lifestyles to urban lifestyles in the city of Eldoret. This provides a natural experiment to study the impact of industrialization on human biology.
• Treadmill Anecdote: An attempt to study how women carry heavy loads on their heads using a treadmill failed because the participants didn't walk naturally on the machine. This highlighted the artificiality of modern exercise equipment like treadmills, which Lieberman humorously describes as a form of torture with origins in Victorian prisons.

Exercise: Definition and Paradox

Lieberman defines exercise as "discretionary voluntary physical activity for the sake of health and fitness." He notes the paradox that while everyone knows exercise is good for them, most people struggle to do it consistently.

• Physical Activity vs. Exercise: Physical activity is any movement, while exercise is a specific type of physical activity done for health and fitness.
• CDC Data: Only about 20% of Americans meet the minimum recommended exercise levels of 150 minutes per week.
• Reasons for Not Exercising: Common reasons include lack of time, stress, and finding exercise unpleasant.
• Evolutionary Perspective on Inertia: Lieberman argues that it's normal to feel inertia towards exercise because humans didn't evolve to do voluntary physical activity in the Stone Age.
• Compassion and Understanding: Instead of shaming people for not exercising, we should help them overcome their instincts and find ways to incorporate physical activity into their lives.

Myths About Exercise and the "Noble Savage"

Lieberman debunks several myths about exercise, including the idea that our ancestors were naturally incredible athletes. He criticizes the "Rousseauian idea of the noble savage," which romanticizes pre-civilization humans as being naturally fit and healthy.

• Common Myths: Ancestors were super athletes, there's a trade-off between speed and strength, it's normal to be less active as you age, there's a perfect type/amount of exercise, sports equals exercise.
• Racist Stereotypes: He points out that some of these myths are rooted in racist stereotypes about certain populations having inherent athletic abilities.
• Ironman vs. Tarahumara Race: He compares the Ironman World Championship in Kona to a Tarahumara foot race (rarajipari) in Mexico to illustrate that both involve rewards, competition, and personal journeys, despite their different cultural contexts.
• Training vs. Life: He notes that for many indigenous cultures, their daily life is their training, unlike the modern Western concept of dedicated exercise routines.
• Physical Activity Level (PAL): PAL is the ratio of total daily energy expenditure to basal metabolic rate. Most animals have PALs of 2-3, while chimpanzees have PALs of 1.4 (lower than sedentary Americans). Hunter-gatherers have PALs around 2.
• Basal Metabolic Rate: The energy required for basic bodily functions. It accounts for about two-thirds of our daily energy expenditure.
• Calories: A unit of energy. Food labels use kilocalories (kcal), which are 1,000 calories.

Smarter Sitting, Smarter Sleeping

Lieberman discusses the myths surrounding physical inactivity, particularly the idea that "sitting is the new smoking." He argues that this statement is misleading and makes people feel unnecessarily anxious.

• Sitting is Normal: Sitting is a normal human behavior, observed in various cultures around the world.
• Better Ways to Sit: There are better and worse ways to sit. Active sitting (using muscles) and breaking up long periods of sitting are beneficial.
• Leisure vs. Work Sitting: The amount of sitting during leisure time is more strongly associated with negative health outcomes than sitting at work.
• Sleep Myths: He challenges the notion that modern life has robbed us of sleep. Research shows that people in non-industrialized societies don't necessarily sleep longer.
• Optimal Sleep Duration: Epidemiological data suggests that the optimal amount of sleep for most people is around seven hours.
• Anxiety About Sleep: Making people anxious about sleep can be counterproductive and lead to a vicious cycle of insomnia.
• Cultural Influences on Sleep: Cultural norms greatly influence sleep patterns. The Western ideal of solitary sleep in a dark, quiet room is not universal.

Walking, Running, and Everyday Strength

Lieberman explores the evolutionary aspects of walking and running, and the importance of strength training.

• Humans and Speed: Humans are not particularly fast compared to other animals.
• Speed vs. Endurance: While there's a trade-off between speed and endurance at the elite level, improving speed can also improve endurance for most people.
• Strength and Power: Strength is the amount of force you can produce, while power is the rate at which you can produce that force.
• Sarcopenia: Age-related loss of muscle mass and strength. Maintaining strength is crucial for healthy aging.
• Sports and Aggression: Sports serve various functions, including training warriors and teaching people not to be reactively aggressive.
• Mixed Martial Arts: Lieberman's experience attending a mixed martial arts fight highlighted how much weapons have changed the nature of human aggression.
• Walking: Walking is the most fundamental form of human physical activity. Hunter-gatherers walk significantly more than people in Western societies.
• Walking and Weight Control: Walking is important for preventing weight gain and maintaining weight loss.
• 10,000 Steps: The 10,000 steps a day goal is somewhat arbitrary, originating from a Japanese marketing campaign.
• Running: Running is the most fundamental form of vigorous physical activity.
• Running and Knee Injuries: The myth that running destroys your knees is largely unfounded. Studies show that running doesn't increase the risk of arthritis and may even promote joint repair.
• Running Technique: Learning proper running technique is important to prevent injuries.
• Aging and Physical Activity: It's problematic to be less physically active as you get older. We evolved to be active grandparents, and physical activity is crucial for maintaining health span.
• Health Span vs. Lifespan: Physical activity primarily increases health span, which in turn increases lifespan.
• Harvard Alumni Health Study: This study showed that physical activity is more important for preserving health as people age.

Exercise as Medicine

Lieberman discusses the medicalization of exercise and its limitations. He argues that it's not so much that exercise is medicine, but that the absence of exercise is harmful.

• Medicalization and Commodification: Exercise has become both medicalized and commodified, which isn't inherently bad, but it hasn't been effective in motivating most people.
• No Optimal Dose: There's no one-size-fits-all prescription for exercise.
• Restoring What's Needed: Physical activity restores what the body essentially needs.
• Anything is Better Than Nothing: Any amount of physical activity is better than none.
• Mortality Rate: Even an hour a week can lower mortality rate by 30%. 150 minutes a week can lower it by 50%.
• Can You Exercise Too Much?: There's limited evidence to support the idea that you can exercise too much.
• Vulnerability to Disease: Physical activity reduces our vulnerability to a wide range of diseases.
• Inflammation: Exercise lowers inflammation, which is a key factor in many chronic diseases.
• Mental Health Benefits: Physical activity has significant immediate benefits on mental health, including improving mood and reducing anxiety and depression.
• Elite Athletics: The focus on elite athletics can be off-putting rather than inspiring.
• Research as a Process: Research is a process of trying to disprove hypotheses, not prove them.
• Natural Experiments: Evolutionary research relies on natural experiments and comparing different populations.
• WEIRD Societies: The world we live in the United States is very WEIRD (Western, educated, industrialized, rich, and democratic).
• Importance of Fieldwork: It's important to study people in different cultures and environments to understand human biology and behavior.