As our evolution slows and industrialization and technology accelerates, a growing body of research suggests that human biology is struggling to keep pace. Many of the chronic stress-related health issues we face today aren’t personal failings or modern inconveniences – they’re the predictable result of forcing Stone Age physiology into a world it was never built for.
A fascinating new study from University of Zurich researchers has investigated whether the rapid and extensive environmental shifts of the current Anthropocene have compromised the fitness of Homo sapiens. In less-evolutionary speak: if the world most of us experience daily is having a profound impact on mental and physical health as a species.
Synthesizing data concerning industrialization and urbanization and health, the researchers argue that there are many signs that humans haven't had time to adapt to the rapid changes in the world over the last century. They cite declining global fertility rates, rising chronic inflammatory conditions and other chronic health trends as signs that we've been struggling on Earth since the Industrial Revolution.
One example they give is our rapid change from hunter-gatherer societies, where humans encountered occasional stressors in the wild, to urban environments where daily challenges have us in a sustained high-alert mode. City noise, air and light pollution, microplastics, pesticides, artificial light, processed foods, sedentary lifestyles and sensory overload are all relatively new experiences for H. sapiens.
"In our ancestral environments, we were well adapted to deal with acute stress to evade or confront predators," explained Colin Shaw, head of the Human Evolutionary EcoPhysiology (HEEP) research group along with Daniel Longman at the University of Zurich. "The lion would come around occasionally, and you had to be ready to defend yourself – or run. The key is that the lion goes away again."
Now, we get little reprieve from an onslaught of stressors – traffic, work, social media, constant sensory stimulation – that trigger those same ancestral biological responses, except without an "off" switch.
"Our body reacts as though all these stressors were lions," said Longman. "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."
Many studies have investigated how this constant hum of elevated stress affects interconnected endocrine systems, which has been linked to anxiety disorders, the development of chronic diseases and reduced life expectancy.
"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," Shaw added, "but on the other hand, some of these industrial achievements are having detrimental effects on our immune, cognitive, physical and reproductive functions."
While it's still debated, the researchers also cite studies into an ongoing global sperm count and motility decline, which has been linked to a range of factors – from obesity to environmental hazards like pesticides and microplastics.
“You could argue that what we’re seeing today is a form of natural selection,” Shaw said. “But letting chronic stress kill people for hundreds of generations until we evolve resistance is clearly not a solution.”
While this is all fairly gloomy, and not all chronic conditions and mental health presentations are due to environmental influences, the researchers believe this work can go a long way in improving lives. And recent studies using advanced genomic analysis suggest we're actually adapting – if not evolving – much faster than scientists previously thought.
“It shows the plasticity of the human genome,” says Karin Broberg of the Karolinska Institute in Sweden, who genetics and environmental toxins. “We’ve spread throughout the world, and we live in very extreme environments, and we’re able to make them our homes. We are like rats or cockroaches – extremely adaptable.”
We do, however, have brains that are far more complex than insects and rodents, which Shaw points out is part of the problem – it's a fascinating case study for evolutionary biologists, but not so practical or helpful when it comes to our comparatively short time on Earth.
"Biological adaptation is very slow," he said. "Longer-term genetic adaptations are multigenerational – tens to hundreds of thousands of years."
So, what can we do to mitigate the toll the world around us takes on our health? The researchers believe we need to change our relationship with nature – to consider it as an important health intervention – and prioritize constructing more sustainable environments. This might be easier said than done, given the world's population and ever-growing demand on natural resources. Not to mention our species' insatiable appetite for making money at the expense of the natural environment. Change, says Shaw, requires both cultural and environmental solutions.
"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," he said. "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.
"We need to get our cities right – and at the same time regenerate, value and spend more time in natural spaces," he added.
"As an evolutionary anthropologist, my earlier work focused on Neanderthals and bone adaptation, which was fascinating in its own right,” Shaw said. “But the challenges we face today feel more urgent. Those with the resources – financial or intellectual – have a responsibility to invest them in solving these problems. To me, it’s a moral imperative to do the right thing.”
At the very least, the researchers note, we should consider getting out into nature as valuable treatment for our health and wellbeing.
The research was published in the journal Biology Reviews.
Source: University of Zurich and MedicalXpress
