Modern stress isn’t normal - our bodies still belong in nature

A provocative new review argues that many of today’s chronic ailments, including our increased stress levels, stem from an evolutionary mismatch.

Our bodies, once tuned for a mobile, nature-immersed hunter-gatherer life, are now immersed in noise, light, pollution, ultra-processed food, perpetual alerts, and chronic stress.

The study was led by evolutionary anthropologists Colin Shaw from the University of Zurich and Daniel Longman of Loughborough University.

The research pulls together evidence across physiology, reproduction, and immunity to make a simple point: culture and technology have changed over centuries, but biology changes over millennia.

“In our ancestral environments, we were well adapted to deal with acute stress to evade or confront predators,” said Shaw.

The textbook scenario is vivid and biologically precise: a rare, short spike of fear, a burst of cortisol and adrenaline, and then a return to baseline.

Ancient stress, modern life

The same neuroendocrine machinery that once saved us now fires all day for traffic, Slack pings, performance metrics, political doomscrolling, and nighttime light.

“Our body reacts as though all these stressors were lions,” Longman said. “Whether it’s a difficult discussion with your boss or traffic noise, your stress response system is still the same as if you were facing lion after lion.”

“As a result, you have a very powerful response from your nervous system, but no recovery.”

That absence of recovery time is the pivot from adaptive to toxic. Persistent activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis nudges blood pressure upward and perturbs glucose control. It also impairs sleep architecture and fans low-grade inflammation.

Layer on modern exposures such as air and noise pollution, microplastics, endocrine-disrupting chemicals, and ultra-processed diets, and the background hum of risk gets louder.

Survival under modern stress

From an evolutionary perspective, fitness boils down to surviving long enough to reproduce and successfully raise offspring. Shaw and Longman contend both legs have been wobbling since the Industrial Revolution.

On the survival side, they point to the rising prevalence of chronic inflammatory conditions and autoimmune diseases. These patterns signal that novel environments push immune function into maladaptive territory.

“There’s a paradox where, on the one hand, we’ve created tremendous wealth, comfort, and health care for a lot of people on the planet, but on the other hand, some of these industrial achievements are having detrimental effects on our immune, cognitive, physical, and reproductive functions,” Shaw said.

Industrial impacts on reproduction

On the reproductive side, they highlight a suite of stress trends. Age at first birth is rising, fertility rates are falling in many countries, and several biological markers have trended unfavorably.

One frequently cited marker is male reproductive health: global reports of declining sperm count and motility since the mid-20th century. “This is believed to be tied to pesticides and herbicides in food, but also to microplastics,” said Shaw.

The researchers are careful not to romanticize pre-industrial life, which carried its own lethal hazards.

Rather, they argue that today’s gains in sanitation, vaccines, antibiotics, and trauma care coexist with insidious new pressures that our bodies are poorly equipped to buffer.

Adaptation moves too slowly

Could we simply evolve past the mismatch? Unlikely on any human timescale. “Biological adaptation is very slow. Longer-term genetic adaptations are multigenerational – tens to hundreds of thousands of years,” said Shaw.

Cultural change – urban design, food systems, work norms – moves orders of magnitude faster than gene frequencies can shift.

That speed gap locks in the mismatch unless we redesign environments to fit our bodies, not the other way around.

Natural spaces reduce stress

Shaw and Longman push for a two-track response: rebuild our relationship with nature and re-engineer cities to respect human physiology.

“One approach is to fundamentally rethink our relationship with nature – treating it as a key health factor and protecting or regenerating spaces that resemble those from our hunter-gatherer past,” said Shaw.

That doesn’t mean abandoning technology; it means deliberately weaving biodiverse, quiet, dark, and green places back into daily life.

Cities redesigned for less stress

On the urban front, they argue for evidence-based design that treats stress, sleep, and immune load as core constraints of daily life, not afterthoughts.

“Our research can identify which stimuli most affect blood pressure, heart rate, or immune function, for example, and pass that knowledge on to decision-makers,” said Shaw.

In practice, the fixes are tangible. Cut nighttime light and noise, expand tree canopy and blue spaces, tame air pollution, create walkable 15-minute neighborhoods, favor stairs over lifts, and nudge food environments toward minimally processed options.

“We need to get our cities right – and at the same time regenerate, value and spend more time in natural spaces,” Shaw added.

Applying mismatch to modern life

People often treat mismatch theory as a big-picture diagnosis. The authors want it to be actionable. Translate the lion metaphor into routines that mirror natural rhythms.

Let stress come in pulses, sleep in real darkness, move throughout the day, eat food in its original form, and seek out green and blue spaces that calm the nervous system and support daily life.

None of that demands a return to caves. It demands a recalibration of defaults at home, at work, and in policy.

The headline claim isn’t that modernity is “bad,” but that our biology still runs Paleolithic firmware.

If we don’t update the interface – our environments – then the operating system responds exactly as designed: by mounting fierce, repeated defenses against “lions” that never leave the room.

The study is published in the journal Biological Reviews.

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