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

With a growing number of US states legalizing marijuana use, scientists and policymakers are once again engaged in a pitched battle over the risks and benefits of THC, the primary psychoactive component of marijuana. Proponents argue that legalization offers important benefits, citing evidence that marijuana may help treat a variety of medical conditions ranging from chronic pain to epilepsy and nausea, while generating substantial revenue–as much as $60 billion according to one estimate–for state and local governments. Legalization, advocates add, also protects public health as safer, regulated sources of marijuana come online to replace black-market alternatives.

But the situation appears to be more complicated than many legalization proponents let on. Critics cite research showing that lax marijuana laws tend to significantly increase use, amplifying the drug’s harmful side effects. For example, some studies show that legalization boosts emergency room visits for psychosis and cannabis hyperemesis syndrome (CHS)—an unpleasant condition characterized by simultaneous screaming and vomiting, often called scromiting. “With the widespread use, increased potency and legalization of marijuana in multiple states in the U.S., CHS may be becoming increasingly common,” the Cleveland Clinic warns.

And while the direction of the association is uncertain (does THC cause mental health disorders or do people with those disorders gravitate toward marijuana) it’s clear the drug is linked to conditions like schizophrenia.

Although drug prohibition is usually the purview of social conservatives, former New York Times reporter Alex Berenson has emerged as perhaps the most forceful opponent of legalization in recent years, arguing in his 2020 book “Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence” that cannabis is far more harmful than the public has been told.

To make sense of these competing claims, Cam and Liza speak with Reason Foundation health care policy analyst Jacob James Rich about his critique of Berenson’s work and the broader effects of drug legalization. Is it time to fully legalize marijuana, or has the public been sold a bill of goods by the drug’s defenders? Let’s take a look.

Jacob James Rich is a policy analyst at Reason Foundation, specializing in prescription and illegal drug regulations. He holds master’s degrees in mathematics and economics and is currently a Ph.D. student at Case Western Reserve School of Medicine. Follow him on X @jacobjamesrich.

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

There’s a growing panic over per- and polyfluoroalkyl substances (PFAS), most recently targeting fluoropolymers used in medical devices. The issue is presented to the public as a grave health threat: “forever chemicals” lurking in medical devices and other seemingly innocuous products that could cause terrible harm. In reality, it’s another campaign by the “activist-tort-lawyer-media complex” that threatens lifesaving technology through fear-driven narratives rather than scientific evidence, says GLP founder Jon Entine. Rather than a danger to public health, fluoropolymers, a subset of PFAS, are critical tools that have saved millions of lives due to their unique properties such as chemical stability and durability.

These materials have proved their safety and efficacy in spades. Yet, activists and tort lawyers, often backed by ideological and gullible media outlets, have demonized all PFAS, leading to calls for blanket bans, as seen in the EU where countries like Germany and Sweden push for restrictions.

Like so many chemical risks, PFAS harms are wildly exaggerated, with recent research showing that low-level exposure primarily comes from water, not consumer products like medical devices. Entine chastises the Environmental Working Group (EWG) for needlessly scaring the public, a tactic echoed by the EPA’s 2019 action plan labeling all PFAS as hazardous despite the fact that this class of chemicals includes over 4,000 compounds varying widely in toxicity. This one-size-fits-all approach ignores toxicology’s bedrock principle of “the dose makes the poison.” In fact, fluoropolymers are not bioavailable due to their high molecular weight, making them perfectly safe when used as intended.

Bottom line: banning fluoropolymers could disrupt medical supply chains and hinder innovation, putting millions of lives in harm’s way. The smarter approach? Perform individual chemical risk assessments to balance safety and utility and reject simplistic activist-driven narratives that disregard sound science.

Podcast:

Join hosts Dr. Liza Dunn Cameron English and Jon Entine on episode 318 of Science Facts and Fallacies as they discuss:

Jon Entine is the founder and executive director of the Genetic Literacy Project. Follow him on X @jonentine.

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

It wasn’t a total train wreck. That’s the best way to summarize the Make America Healthy Again (MAHA) Commission’s May 22 report addressing rising rates of chronic childhood diseases in the U.S. Led by Health and Human Services Secretary Robert F. Kennedy Jr., the Commission’s 68-page document mixed some good science with a lot of speculation and inference that could mislead the public as much as inform them about how to keep their kids healthy.

The report identified four potential drivers of obesity, diabetes, autism, and mental health disorders: poor diet, chemical exposure, lack of physical activity, and overmedicalization. Over 40 percent of nearly 73 million U.S. children have at least one chronic health condition, the document noted, with obesity rates in children over six exceeding 20 percent—a troubling increase since the 1970s. In what may be its most science-based analysis, the Commission observed that most US children don’t get the recommended amount of physical exercise each week, and more than 50 percent of American teens spend nearly nine hours daily in front of screens outside of school, correlating with reduced physical activity, sleep deprivation, and increased risks of obesity and mental health issues.

Although the report correctly diagnosed some of the critical health issues facing children, its prescriptions were often disappointing. For example, the Commission’s claims about chemical exposures, including pesticides, pharmaceutical drugs and consumer products, were just wrong, falsely asserting that these exposures could cause a “wide range of toxic effects” without robust evidence. In fact, the report’s sources sometimes directly contradicted the Commission’s conclusions, raising suspicions that the authors had predetermined points they were going to make regardless of what the evidence actually showed. This weakens the Commission’s credibility and risks vilifying widely used chemicals that help us protect public health and produce an abundant food supply.

The report called for further research and policy recommendations by August 2025, though it remains to be seen if those conclusions will be based on the “gold standard science” RFK, Jr. so frequently touts to the media.

Join hosts Dr. Liza Dunn and GLP contributor Cameron English on episode 317 of Science Facts and Fallacies as they discuss:

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

Starting around 2010 or 2011, events converged in ways that made prescription pills less widely available. Law enforcement cracked down on pill mills, the maker of Oxycontin made the pill harder to crush, physicians tightened their prescribing practices, and more states created prescription registries to help identify people who were obtaining prescriptions by “doctor shopping”—that is, by seeking prescriptions from multiple physicians at the same time.

While this initial response was necessary to clamp down on unethical prescribing, it metastasized into a broader campaign against medical opioid use more generally, in which legitimate patients who needed pain control were denied access to medicine and their physicians were prosecuted and often convicted for drug trafficking. It’s an approach that unfairly penalizes upstanding doctors, disrupts patient care, and raises concerns for public health: many people have been left to languish in pain so severe they take their own lives or overdose after turning to street drugs like heroin.

The ongoing anti-opioid campaign has blurred the line between responsible medical practice and illegal activity, with laws like the Controlled Substances Act, meant to combat drug trafficking, being punitively applied to clinicians. On this episode of facts and fallacies, author and medical malpractice attorney Ron Chapman joins Cameron English to discuss how we can restore the balance between accountability and compassion, protecting the public from bad actors while providing appropriate medical care to patients who need it.

Ron Chapman is a federal criminal defense attorney and author of the book Truth and Persuasion. Visit his Substack and follow him on X @RonChapmanAtty.

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

The disinformation cycle itself thrives on social media, where wellness influencers and ideological outlets amplify fear-driven narratives and exploit public skepticism of institutions like the FDA and CDC. But rather than fixing real problems within these public health agencies, the bipartisan wellness crusade uses them as fodder for its own idiosyncratic and often dangerous policy proposals.

This bipartisan convergence threatens public health innovation, particularly in agriculture and medicine, where life-saving technologies face unwarranted vilification from activists who wrongly see such innovations as inherently harmful. The solution to these distorted narratives? Healthy skepticism and a willingness to challenge our own ideological assumptions. Too many people today allow their existing beliefs to mold their views on scientific and medical questions, when they should be guided by rational thinking and data wherever possible.

Join hosts Dr. Liza Dunn and GLP contributor Cameron English on episode 315 of Science Facts and Fallacies as they discuss:

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

The same basic toxicology lesson is a helpful counter to misleading scare claims about food dyes, herbicides, and pharmaceutical drugs that proliferate across social media. These substances have legitimate medical and industrial uses, and their toxicity depends on dosage and route of exposure—not their mere presence in your environment or body. Caffeine, to cite another common example, is a naturally occurring neurotoxin that plants use to combat hungry insects, a fact that doesn’t stop 85 percent of Americans from consuming it daily as a mild stimulant with typically no dangerous side effects.

The problem is that myriad bad actors (wellness influencers, activists and even ideological scientists) exploit the term “toxic” without context, capitalizing on the public’s limited knowledge of toxicology and chemistry to sell their wares, whether those are sham supplements, diet books or chemical bans they want voters to support.  The solution to each scam is a heavy dose of critical thinking to navigate the nonsense. Equipped with a baseline scientific understanding, we can discern fact from fear-driven propaganda.

Join host Cameron English and special guest Dr. Kevin Folta on episode 314 of Science Facts and Fallacies as they break down:

Kevin M. Folta is a professor, keynote speaker, and podcast host. Follow Professor Folta on X @kevinfolta

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 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

Reed’s allegations, detailed in a 2023 Free Press article and a sworn affidavit to Missouri Attorney General Andrew Bailey, claimed the center harmed vulnerable adolescents, some of whom later regretted their transitions. “During my time at the Center, I personally witnessed Center healthcare providers lie to the public and to parents of patients about the treatment, or lack of treatment, and the effects of treatment provided to children at the Center,” she declared in her affidavit. These cases included shocking examples of children suffering from depression, anxiety, ADHD, eating disorders, and even autism receiving puberty blockers rather than the patient-specific care they really needed.

Reed’s actions triggered a series of investigations, ultimately leading Washington University to shutter its pediatric gender clinic. The school and some of its allies have dismissed Reed’s claims as “unsubstantiated,” asserting compliance with standards set by organizations like the American Academy of Pediatrics (AAP). However, AAP’s guidelines on youth gender medicine are based on recommendations from advocacy groups like the World Professional Association for Transgender Health (WPATH), which in turn cites guidelines from—the AAP. This circular citation amounts to little more than a Potemkin village, “an apparent consensus on key areas of practice for which evidence remains lacking,” as a 2024 review in the British Medical Journal put it. The guidelines from US-based advocacy groups also flout the growing global consensus of medical professionals who doubt the safety and efficacy of gender-affirming care.

Reed has rebuffed allegations that she has “been brainwashed or paid off—or probably even both—by conservatives.” Striking a more scientific tone, she says her decision to blow the whistle on Wash U came down to one thing: “my realization that I … was wrong.” Before Wash U closed the pediatric gender clinic, it also instituted major policy changes, requiring written parental consent before prescribing gender-affirming drugs and asking for custody agreements prior to a child’s first visit. Reed says these changes were an acknowledgement that her allegations were well-founded.

After leaving Wash U, Reed founded the LGB Courage Coalition, a nonprofit challenging youth gender medicine. She’s currently testifying in state legislatures across the country in an effort to outlaw pediatric gender interventions.

On this episode of Facts and Fallacies, Reed joins Dr. Liza Dunn and Cam English to challenge the questionable science behind the ethically fraught field of youth gender medicine.

Jamie Reed is the executive director of LGB Courage Coalition. Visit the group’s website and follow here on X @JamieWhistle

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