Half gone.
That is what the data suggests has happened to average male testosterone levels since the 1970s. Prof Hagai Levine called it “mind-blowing.” He urged everyone to “wake up.” The alarm bells are ringing loud across the scientific community and beyond.
Levine’s team isn’t just talking hormones. They’ve previously flagged a drop in sperm counts, a trend some media dubs “spermageddon.” It has become a political fixation. Robert F. Kennedy Jr., the US health secretary, calls it an “existential crisis.” Online “manosphere” groups use it as proof that society is weakening men. Meanwhile, health experts worry about endocrine-disrupting chemicals. Air pollution. Global heating. The usual suspects.
Not everyone buys the doomsday scenario.
“There’s a tendency to pick the data that matches our worldview,” said Prof Allan Pacey from Manchester. If you think the world is ending, sperm decline makes perfect sense to you.
Pacey’s recent analysis, which used more consistent measurement methods, found no evidence that sperm counts are dropping significantly. The quality of the sperm might be worsening, but the number is holding steady. Other researchers have found mixed results trying to replicate Levine’s work.
Does Pacey worry about infertility? Sure. He thinks there’s a problem. But he doesn’t believe it’s the vanishing act Levine predicts. Shanna Swan, Levine’s co-author, has even suggested sperm counts could hit zero by Prof Allan Pacey is not convinced.
The Obese Body Budget
Where there is less disagreement is on the connection between male reproductive health and overall health. Men are getting heavier. That changes things.
Excess body fat turns testosterone into estrogen. It disrupts hormonal signaling. One study found every point rise in BMI links to a 2% drop in testosterone. Less testosterone often means lower sperm production. Plus, carrying extra weight heats up the scrotum. Sperm hate heat. They need it cooler than your core temperature to survive. Diabetes doesn’t help either, causing DNA damage and erectile dysfunction
Prof Channa Jayasena of Imperial College London sees it as a metabolic crisis.
“Obesity could easily account
Environmental Myths and Microplastics
We have thousands of studies on environmental toxins. Microplastics are now in seminal fluid. Rat offspring exposed to Pfas have abnormal sperm. Some Italian research linked pollution to smaller penises. Another US study found they were getting 24% longer. The contradictions are messy, but the hypothesis is always the same. Endocrine-disruptors are rewiring development.
The problem? The race to publish.
Public interest in microplastics is feverish. Basic controls are getting skipped. Bold claims are being made on thin evidence. Just because microplastics are sitting in testicle tissue doesn’t mean they’re causing havoc. They might just be sitting there, inert, doing absolutely nothing.
“It’s easy to extrapolate that this presence must be bad. But we need to be careful.” – Prof Rod Mitchell, Edinburgh.
Mitchell’s experiments are among the most controlled available. He tested common suspects. Phthalates. BPA. The plasticizers that make headlines. His result? No change in testosterone. No change in testis development. The animal models might be misleading us.
He sits in the middle on this. Uncertain. Cautious. Levine acknowledges the biological mechanisms aren’t fully understood. He argues for the precautionary principle anyway. We don’t need 90% certainty.
“Do we jump off a cliff with a parachute to see if it works?” Levine asked. No. We step back from the edge.
The Clinical Void
For men trying to have children, this uncertainty is a nightmare. The window is short. The cost is high. The information is contradictory. Prof Christopher Barratt of Dundee notes that male infertility is often treated as an afterthought in fertility clinics run by gynaecologists Women get scanned and tested. Men wait months or even years.
The basics are boring but essential.
- Physical examination
- Medical history
- Semen analysis
We haven’t updated semen analysis since the 19 950s. It’s blunt. Either you have no sperm, or your sperm are slow. If the latter, you use centrifuge to spin out the heavier, healthier sperm. Pacey calls it “blunt force over ignorance.” It works. Barely.
Into this gap steps marketing.
Social media influencers and online companies are selling supplements and tests. Many aren’t endorsed by the Human Fertilisation and Embroyology Authority. A dangerous narrative is emerging around “low T.” Men are prescribed or buying testosterone online.
It’s counter-intuitive. Testosterone therapy stops sperm production. The body sees enough hormone circulating. It shuts down internal production. It’s like turning on a portable heater and switching off the boiler. You need high local levels in the testicle, not just in the blood. Jayasena warns of a “self-inflicted problem” of indiscriminate use. It is rising in the UK, US, and Australia.
Silicon Valley and AI
Is there hope? Yes. Technology might save the day.
Microfluidics devices are racing sperm through microscopic mazes to find the fitter cells. DNA fragmentation tests are improving. Currently, we just see the percentage of damaged DNA. We can’t yet pick the perfect single cell.
Given that a single ejaculation releases millions of cells, the data is perfect for machine learning. Barratt says sperm and AI are made for each other. They are different, numerous, and measurable.
On the radical edge, startups like Paterna claim to grow functional sperm in a lab from stem cells. They created embryos from these lab-grown cells. The goal is to help men who have zero sperm.
“I’m very optimistic things will look different in five years,” said Barratt.
For now, the panic isn’t warranted. Mitchell isn’t worried about imminent human extinction. Some predictions of zero sperm count by 2050 sound ridiculous. Populations are declining anyway, for social reasons, not just biological ones.
The problem might not be the sperm. It might be the world we’ve built around it. We’re looking at the biology. We might be missing the bigger picture.
