Are we in the midst of a male reproductive crisis? The question has generated one of the most polarized debates in modern reproductive science, and a major investigation by The Guardian’s science correspondent Hannah Devlin provides the most comprehensive portrait yet of the evidence, the personalities, and the politics driving it.
The alarmist case
The crisis narrative rests on two pillars. The first is a series of meta-analyses led by Professor Hagai Levine of the Hebrew University of Jerusalem and Professor Shanna Swan of the Icahn School of Medicine at Mount Sinai. Their 2017 study in Human Reproduction Update reported a 52.4% decline in sperm concentration and a 59.3% decline in total sperm count between 1973 and 2011. A 2022 update showed the decline accelerating to approximately 2.5% per year after 2000, a trajectory that Swan said, if extrapolated, could reach zero by 2045.
The second pillar is new data on testosterone. Levine’s team recently analyzed studies covering 118,593 men across Israel, the United States, Brazil, Finland, and Denmark, finding a 54% decline in average testosterone levels between 1972 and 2019, a drop of more than 1% per year.
“It is mind-blowing that testosterone has declined by 50%,” Levine told the Guardian. “This is a lot. Wake up people. Wake up.”
Environmental chemicals, phthalates, bisphenol A, PFAS, and microplastics, are the most frequently cited culprits, along with modern lifestyle factors including obesity, diabetes, and mobile phone use.
The skeptical countercase
But a vocal group of equally respected scientists argues the crisis is overstated. Professor Allan Pacey of the University of Manchester, a leading skeptic, points out that his own group found no evidence of substantial decline when using consistent measurement techniques in Danish sperm donors over decades. “There’s a tendency to pick the data that supports our viewpoint,” Pacey said. “Sperm count decline isn’t one that I worry about.”
Professor Rod Mitchell of the University of Edinburgh has conducted highly controlled experiments on human fetal testis tissue exposed to phthalates and BPA at relevant concentrations, and found no effect on testosterone production or testis development. “The animal studies are misleading,” Mitchell said. Regarding microplastics found in seminal fluid and testicles: “They could just be sitting there inert and not doing anything.”
Professor Channa Jayasena of Imperial College London argues that obesity alone could explain the entire testosterone decline. Each 1-point increase in BMI corresponds to a 2% decrease in testosterone, and global obesity rates have risen substantially over the same period.
The middle ground
Despite the deep disagreements, there are areas of consensus. Sperm quality, motility, morphology, and DNA fragmentation, does appear to be deteriorating even if total count trends are contested. Clinical systems for diagnosing male infertility remain woefully inadequate, with many IVF services still reliant on what critics describe as 1950s-era semen analysis.
The investigation also examines an emerging self-inflicted problem: the rise of indiscriminate testosterone replacement therapy (TRT), bought online or prescribed without a genuine medical need. “It’s like a thermostat,” Jayasena explained. “If you put a heater in the lounge it will switch off the boiler. You need very high levels of testosterone in the testes to make sperm.”
On the precautionary principle, Levine argues for action even absent definitive proof: “Let’s say that there is a 1% chance that something we are doing now would make reproduction extremely rare in 100 years’ time. Should we do something about it? I think yes.”
The Guardian investigation makes clear that the question of a male reproductive crisis is far from settled, but the stakes, on all sides, could hardly be higher.
Sources:
1. Devlin H. “Spermageddon: is the world facing a male reproductive crisis?” The Guardian. 11 Jul 2026. https://www.theguardian.com/society/ng-interactive/2026/jul/11/spermageddon-world-facing-male-reproductive-crisis