The story goes something like this: humans evolved in hunter-gatherer settings, facing acute, intermittent stressors like predator encounters that triggered intense fight-or-flight responses followed by recovery. These environments fostered physiological adaptations suited to natural rhythms, physical activity, and periodic challenges.

In contrast, today’s industrialized, urbanized world—home to over 4.5 billion people, projected to reach 6.5 billion by 2050—imposes a constant stream of low-level stressors, from traffic noise to relentless digital stimulation. Evolutionary anthropologist Colin Shaw of the University of Zurich argues this “mismatch” places a chronic stress load on our bodies, as our nervous systems react to modern pressures “as though all these stressors were lions… you have this very powerful response… but no comedown.”

This mismatch manifests in widespread health declines. Physically, it likely contributes to elevated blood pressure, weakened immune function, rising autoimmune diseases, and plummeting fertility rates, with sperm counts and motility dropping since the 1950s. Mentally, constant stimulation impairs cognitive function and sustains tension.

Shaw and his colleagues speculate that environmental factors like pesticides and microplastics are overlooked drivers of these harms, though they wrongly exaggerate the risks posed by these technologies and, more importantly, the higher living standards they enable—including free time to explore nature.

However, many harmful effects attributed to modern environments are probably amplified by the erosion of traditional social bonds and community structures. The rise of our modern, globalized civilization hasn’t just altered our environment but rapidly weakened intermediate associations—such as family, neighborhood, church, and community groups—that once provided meaning, security, and mutual support.

This complementary thesis suggests that our hardwired need for community remains vital to our well-being, and its increasing absence in contemporary society compounds health declines far beyond environmental factors alone.

Join Dr. Liza Lockwood and Cam English on this episode of Facts and Fallacies as they take a closer look at the risks and benefits of industrialized society:

Dr. Liza Lockwood is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Follow him on X @camjenglish

Critics aren’t convinced, however. They contend that obesity is a behavioral abnormality and a risk factor for real diseases, not a discrete pathology. Writing in the journal Nature in 2014, Dr. David Katz summed up this perspective. “Our bodies, physiologies and genes are the same as they ever were,” he argued. “What has changed while obesity has gone from rare to pandemic is not within, but all around us.” In short, an abundant food supply and marked decrease in physical labor over recent decades have turned a normal physiological response—storing excess calories for later use—into a public health threat. Humans are wired for an environment characterized by energy scarcity, where intense exertion is required to gather the calories necessary for survival, a dynamic that persisted well into the 20th century.

Proponents of the disease model of obesity, including the American Medical Association (AMA), which classified obesity as a disease in 2013, emphasize its complex etiology: genetic predispositions, hormonal dysregulation (e.g., leptin resistance) and socioeconomic barriers contribute to energy imbalance, akin to hypertension or diabetes. Advocates also say recognizing obesity as a disease destigmatizes patients, enhances insurance reimbursement for treatments and spurs research funding—vital as obesity drives comorbidities like cardiovascular disease and type 2 diabetes.

So, is obesity a disease or a harmful lifestyle choice? Are those two definitions mutually exclusive? Join Cam English on this episode of Facts and Fallacies as he examines the obesity-disease hypothesis.

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Follow him on X @camjenglish

Over the last decade, a growing chorus of scientists has declared that biological sex is not binary. Properly assessing human diversity requires us to apply a broader definition of this word, the argument goes. “The term ‘biological sex’ has been used to sort all people into one of two groups,” a May open letter from hundreds of scientists to the UK’s Minister for Women and Equalities asserted. “However, a strict, binary categorization is an over-simplification.”

The letter – signed by more than 350 academics, clinicians, and activists – is carefully argued, meticulously footnoted—and fundamentally mistaken about a basic biological reality. “Such statements … are most astounding as they ignore or even reject the well-established biological concept of sex and, thus, they ultimately deny fundamental principles of biology,” a team of evolutionary biologists wrote in 2023, responding to similar statements published by several academic journals.

Evolution, a scientific concept as well established as gravity, excludes the idea of a sex spectrum by confirming that biological sex is a binary trait in humans and most mammals. Evolution has shaped organisms to maximize reproductive success, resulting in two distinct sexes—male and female—defined by their roles in producing sperm or eggs. Males produce small, mobile gametes (sperm), while females produce larger, resource-heavy gametes (eggs). This binary system, driven by the need for genetic recombination, is a fundamental mechanism of sexual reproduction, observable across species. “With a few exceptions, all sexually reproducing organisms generate exactly two types of gametes that are distinguished by their difference in size,” the 2023 essay  added.

Intersex conditions, which are rare (approximately 0.018% of the population) and often involve ambiguous genitalia or chromosomal variations, are medical anomalies, not evidence of new sexes or a spectrum. They do not alter the binary framework, as they typically derive from disruptions in male or female developmental pathways.

The notion of a “sex spectrum” conflates sex with gender identity or secondary sexual characteristics, ignoring the objective, gamete-based definition of sex. Evolutionary biology shows no mechanism for a continuum of sexes. Scientists who endorse the sex spectrum often prioritize social or ideological considerations over empirical evidence, denying the binary reality established by evolutionary pressures.

By rejecting these basic facts, sex-spectrum advocates undermine the rigor of biology, misrepresenting a field that relies on testable, reproducible evidence. They also fuel mistrust of science, making it even harder for experts to convince the public that their scientific and medical claims are grounded in solid evidence.

Join Dr. Liza Dunn and Cam English on this episode of Facts and Fallacies as they discuss the science of reproduction and raise some critical questions about the sex spectrum.

Dr. Liza Dunn is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Follow him on X @camjenglish

Join hosts Dr. Liza Dunn and GLP contributor Cameron English on episode 313 of Science Facts and Fallacies as they break down these latest news stories:

Activists routinely blame modern agriculture, plant breeding, and pesticide use for reduced nutrient density in fruits and vegetables, but this assertion is oversimplified and exaggerated, ignoring the complexities of food production and consumption. Often overlooked is that modern breeding focuses on sensory appeal and post-harvest durability to increase consumption of nutrient-rich produce and reduce food waste, despite slightly lower nutrient density in some produce.

A growing body of science is fueling debate about the downsides of pornography consumption. Although studying porn use is ethically fraught – we can’t put people in a room and watch them watch it – some research indicates that porn alters brain function, hijacking the reward system and impeding impulse control, potentially leading to compulsive behavior. Still, the evidence is inconclusive, with conflicting research and a lack of consensus on whether these changes are harmful or significant over the long term.

A recent study comparing fraternal and identical twins, over 9,000 individuals in total, found that genetic factors partially influence how much people enjoy music, accounting for distinct and overlapping variations in musical appreciation. The study suggests that while environment and upbringing play a role, inherited traits contribute to a person’s affinity for music. The results could encourage further investigation into the evolutionary roots of music appreciation.

Dr. Liza Dunn is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Visit his website and follow him on X @camjenglish

Join hosts Dr. Liza Dunn and GLP contributor Cameron English on episode 311 of Science Facts and Fallacies as they break down these latest news stories:

Sugar is addictive. Girl Scout cookies help fuel deforestation. Chemicals in cosmetics damage your hormones. Each of those claims is false, yet NPR has promoted them all over the years. But now that right-wing activists are making similar claims, the publicly funded news outlet is suddenly pro-science, dismissing allegations about “toxic” Girl Scout cookies as unfounded. Enough of the double standards; it’s time for journalists to provide consistent, evidence-based reporting to counter unscientific claims, regardless of the politics of the people who make those assertions.

Meanwhile, the MAGA-driven culture war against mRNA vaccines is a true setback for science. Outrageous allegations, e.g. mRNA shots are untested gene therapies, have lowered vaccination rates, threatening public health and gutting support for vaccine development that could help treat serious diseases, including some cancers. Why have so many conservatives become hostile to mRNA technology, and what do we do about it?

Looking ahead, future generations may see AI reshape work, health and culture, with enhanced cognition and virtual realities blurring human boundaries and even changing the direction of evolution. How do we prepare for the unprecedented tech-driven challenges future generations will confront?

Dr. Liza Dunn is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Visit his website and follow him on X @camjenglish