In the past, staying active was a basic requirement for survival. Voluntary exercise, as we know it today, would have been completely foreign. Dr. Daniel Lieberman, a leading evolutionary biologist and Harvard professor, argues that understanding how our evolutionary past clashes with our modern lifestyles is key to solving today’s chronic health problems.
Dr. Lieberman’s academic journey began with a fascination for human skulls, but his focus eventually broadened to explore the human body’s adaptations and their limits. His fieldwork has taken him across the globe—from the Maasai people in Kenya to the Tarahumara in Mexico—to learn how traditional ways of living offer clues about modern health challenges.
Lieberman’s core idea is straightforward: humans evolved in environments where physical activity was not optional. Movement was essential. A turning point in his thinking came when a Tarahumara elder, puzzled by Lieberman’s questions about “training,” replied, “Why would anyone run if they didn’t have to?” This moment made Lieberman realize that exercise as a separate activity is a very recent and unnatural development.
Today, Lieberman argues, we face a “comfort crisis.” Our modern world—with escalators, cars, and cushioned shoes—is designed to minimize effort. As a result, rates of preventable diseases like heart disease, diabetes, and certain cancers have surged. Yet only about 3% of healthcare spending goes toward prevention, even though about 75% of diseases are preventable.
One major change Lieberman made in his own life was to start strength training. Though he had always been a fan of walking and running, he realized that losing muscle mass—a process called sarcopenia—leads to greater health risks as we age. Now, he makes it a point to lift weights at least twice a week.
Lieberman also challenges the idea of retirement as we know it. In traditional societies, elders stayed active, contributing to their communities and maintaining their physical and mental health. In contrast, modern retirement often leads to inactivity, accelerating health decline.
He debunks other myths too. For example, sitting itself isn’t harmful; it’s sitting without movement for long stretches that’s the real issue. Studies show that people in traditional societies sit about as much as Westerners but interrupt their sitting more often by moving around.
Another myth is the idea that everyone needs eight hours of sleep. Research shows that people in non-industrial societies usually sleep about six to seven hours a night, with seven hours often being ideal for health.
Even the famous “10,000 steps a day” goal wasn’t based on science. It started as a marketing idea in Japan. However, studies suggest that aiming for around 7,000 to 8,000 steps a day provides substantial health benefits.
At the heart of Lieberman’s argument is the idea that while genetics play a role, the environment has a much bigger impact. The saying “genes load the gun, environment pulls the trigger” captures it well.
Traditional hunter-gatherer populations, who don’t rely on processed foods or modern conveniences, have much lower rates of diseases like diabetes and dementia. Their constant low-level activity and natural diets give them powerful protection against many modern illnesses.
Physical activity does more than just maintain muscles. It activates genes that repair DNA, boosts the number of mitochondria (the energy producers in cells), and slows down brain aging. It is one of the most effective ways to fight the aging process.
According to Lieberman, we don’t need to live like cavemen to be healthy. Instead, we can make small changes that encourage healthier choices: making nutritious foods cheaper, taxing sugary products, designing cities that promote walking, and encouraging physical activity at work. Some companies, like one he studied in Sweden, even mandate weekly group exercise sessions with great success.
Reframing exercise as “adult play”—through dancing, sports, or games—can also make movement more fun and sustainable.
In the end, “comfort” has quietly become one of the biggest threats to our health. Lieberman’s message is clear: embracing occasional physical discomfort and better dietary habits is essential if we want to live longer, healthier lives.
The old saying “use it or lose it” isn’t just about muscles—it speaks to the very foundation of human health.
Our evolutionary journey isn’t over. It’s being written every day, with every choice we make.
Dr. Daniel E. Lieberman is a renowned American paleoanthropologist and the Edwin M. Lerner II Professor of Biological Sciences at Harvard University, where he chairs the Department of Human Evolutionary Biology. He is best known for his research on the evolution of the human head and body, particularly the endurance-running hypothesis, which suggests that humans evolved to run long distances for hunting and scavenging.
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