A rash of sensational headlines in recent months have warned of a rising infertility crisis in men as sperm counts plummet. Some outlets have claimed that plastics are behind the great sperm dieoff. But it turns out the truth about fertility could be much more complicated.
Researchers have suspected since the early 1990s that human sperm counts may have been on the decline, but a seminal study in 2017 really changed the conversation. The study in question, referred to Levine, et al. after its authors, is a metanalysis of a bunch of other studies on sperm counts between 1973 and 2011. The analysis showed sperm counts in samples taken from Western men declined by more than 50% over that time period.
These striking findings sparked a media frenzy upon the study’s publication, with headlines trumpeting about how sperm counts “could make humans extinct.” One of the coauthors of the Levine, et al. paper, Shanna Swan, published her own book this year on the declining sperm phenomenon that sparked the new wave of headlines, arguing that endocrine disruptors in plastics, chemicals, and other products are largely to blame for shaking up the natural order.
“Simply put, we’re living in an age of reproductive reckoning that is having reverberating effects across the planet,” the book’s prologue reads. (Subsequent chapters advise readers to trash items in their house like mothballs, air fresheners, scented candles, and antibacterial soaps in the name of sperm health, and advise parents to get rid of plastic bins for toys in favor of baskets.) “If these alarming trends continue unabated, it’s difficult to predict what the world will look like in a hundred years. What does this dramatic decline in sperm count portend if it stays on its current trajectory? Does it signal the beginning of the end of the human race—or that we’re on the brink of extinction?”
It’s enough to make anyone want to throw out all their Tupperware, watch The Handmaid’s Tale as a documentary, and take notes on what we can all expect for the coming spermpocalypse. But other experts say that there’s still much more work to be done before we sound the alarm.
First, there’s the question of whether or not we’re experiencing some sort of massive sperm die-out in the modern age. In a paper published earlier this month in Human Fertility, some scientists argue the panic is driven in large part by some structural problems in the Levine, et al. study.
“The issues with this study were these core basic issues that affect the field of sperm decline research as a whole,” said Marion Boulicault, one of the lead authors on the recent paper. Boulicault stressed that the Levine, et al. study is very empirically sound, and there’s nothing wrong with the statistical analysis itself. However, she said, it exemplifies “implicit assumptions that get built into the research and seem so plausible that they become invisible.”
Boulicault said one of the core issues is that the study assumes men in the 1970s had the ideal level of sperm—she noted there’s no “specific scientific evidence” for that—and doesn’t sufficiently acknowledge that there’s a wide range of sperm counts that men can naturally have and still be fertile. Current World Health Organization standards dictate that a “low” sperm count is less than 15 million sperm per milliliter of semen. Notably, the decline in sperm counts Levine, et al. documented went from an average of 99 million sperm per milliliter in the 1970s to 47 million sperm per milliliter in the early 2010s. The decline doesn’t necessarily mean the end of our society as we know it; men are still fertile, they’re just working with a little less ammunition.
I reached out to Swan to see if she had any thoughts on the paper by Boulicault and her colleages. Swan’s publicist sent me back a quote her co-author, Hagai Levine, gave to another outlet: “We are glad that our paper aroused discussion and raised attention to the much neglected issue of male reproduction. The response paper does not add new data. Of course, there is always distinction between facts and interpretation.”
Another issue Boulicault and her coauthors point out is how the conversation about low sperm counts has been falsely shaped based on how the original research divided its results. The Levine, et al. study separates its findings into “Western” countries (those in Europe, Australia, and North America) and “other” (basically, everywhere else, a group that includes places as disparate as Tanzania and China). This move mostly reflects the fact that there was a larger sample size of studies conducted in “Western” countries versus “other” places, and that the proportion of the results wasn’t productive to compare.
But the resulting message that was picked up by the media is that there was a specific crisis in the developed world, leading to a barrage of panic-induced coverage that, implicitly or explicitly, foresaw doom for a very specific group of people with a very specific lifestyle. The correlation of “Western” with “white” in the public imagination also meant that a subset of reactionary media characters have really taken this narrative and run with it.
Conspiracy theorist Alex Jones connected the Levine, et al. findings with his own theories that the drop in sperm counts was due to the feminization of men, while right-wing YouTuber and Proud Boys member Joe Biggs said in a video responding to the study that “men [are] going from being alpha males to essentially being cucked-out, skinny-jeans-wearing, man-bun-having, feminized little girls.”
While conspiracy theorists have seized on, well, conspiracies, people concerned about the environment have tied the decline in sperm to the plastic pollution crisis. Yet the small cluster of findings in the non-Western world—some of which are from countries like India and China with serious levels of industrialization and pollution—surveyed in the Levine, et al. study don’t reflect the same declines in sperm count as the larger group of Western studies. That doesn’t mean that this group is not somehow impacted by whatever is messing with sperm, but rather more research on sperm counts is urgently needed in all corners of the world.
Richard Sharpe, a professor at the University of Edinburgh’s MRC Center for Reproductive Health, said that there’s no scientifically infallible way of proving that sperm counts are historically falling. “Until we can invent time travel and go back and sample men from the past and then compare it with present-day things done in the same lab—and we’re not going to do that, obviously—then we can never be certain,” he said.
But Sharpe, who called the new paper in Human Fertility “laughable,” said he’s “100% convinced” that men across much of Europe—and possibly other areas of the world—are experiencing sperm counts today that could cause problems for those men trying to get pregnant with female partners, especially if those partners are older, as is the case with many modern couples. These lower levels of sperm don’t necessarily mean the men are infertile, he said, but lower sperm counts mean “it will take them longer to get their partner pregnant, and in a modern societal context that’s a recipe for couple infertility.”
But Sharpe also cautioned against panicking over plastic or giving it an outsize role in what’s going on. Counter to Swan’s claims in her book, Sharpe said that in his estimation, the comparatively large amount of research done on the effects of phthalates on reproductive health over the past few decades has shown “no convincing evidence that these have effects on humans.” Many of these studies, he said, are based on lab animals’ exposure to high levels of the stuff in plastics that human beings have low exposure to in our day-to-day life. Meanwhile, he said, other areas of research, like on pregnant women living near industrial areas or the role of over-the-counter drugs like Tylenol during pregnancy, have been comparatively overlooked.
“Are the effects we’re seeing ascribable to the plastics themselves, or the modern lifestyle that exposes us to those plastics?” he said. “We’ve been looking under the wrong lamppost. What we’ve been looking at is chemicals we’ve been exposed to at low levels, but on the other end of the scale we’ve seen incredible use of pharmaceuticals that we’ve been repeatedly exposed to at high levels.”
There’s so much that we don’t know about how our bodies work and, if you get too far into the internet rabbit hole, everything can seem to be a threat, from plastic cling wrap to body lotion to spending too long in damp spaces. It’s very clear that we’re going to need to mobilize an army of researchers to figure out how endocrine disruptors, industrial pollution, and other aspects of modern life are impacting us. But it’s always worth examining the forces shaping the conversations around pieces of scientific research, especially ones that induce panicky and prophetic headlines that play into specific tropes.
And regardless of which factor of modern life you’re examining, the conversation demonstrates how tricky it is to design sound research on the effects of certain inputs on human fertility.
“What are you going to do, administer a bunch of Tylenol and wait 25 years to find out if there’s an effect on sperm count?” Sharpe said. “Who’s going to give you the funding for that? The cards are sort of stacked against researchers.”