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Don’t worry about your sperm count A testy book fails to explain why mankind is doomed

Mankind's sticky ending: Woody Allen dressed as a sperm. Credit: United Artists/Getty

Mankind's sticky ending: Woody Allen dressed as a sperm. Credit: United Artists/Getty


March 3, 2021   9 mins

Let’s imagine that you think the world is facing a real problem, and it’s not paying enough attention to that problem. Say you think, I don’t know, that grazing deer kill young trees and damage ecosystems, and that we ought to reintroduce apex predators in order to reduce their populations and restore natural forests. 

Obviously, you don’t think this is the only problem in the world, and you don’t think that all of humanity’s resources and ingenuity should be dedicated to finding ways of getting lynx and wolves released into north-west Scotland; we should still worry about carbon emissions and so on. But you think some of humanity’s resources and ingenuity should be devoted to it. Say you think that 0.01% of society’s time and effort should be spent thinking about lynx, instead of none at all.

But you’re only one person, representing one 70-millionth of the British population. Shifting society’s behaviour even by that small amount means convincing thousands of people to agree with you. You would need to dedicate all of your time, all of your effort, if you are to have any chance whatsoever of moving the dial even a little bit. 

So you end up looking obsessive and weird – “why are you shouting about lynx all the time? Don’t you know there are other problems in the world?” – even if you’re completely right that the lynx-shortage is a bad thing. Scott Alexander calls this the “fallacy of reversed moderation”. The lynx-advocate might even be tempted to overstate the scale of the problem and the efficacy of the solution: “Deer overpopulation is causing children’s brains to shrink; only introducing lynx can restore normal-sized cortices to our nation’s young!”

This is, I think, part of what is going on in Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperilling the Future of the Human Race, by Shanna Swan and Stacey Colino.

In 2017, Swan, along with other scientists, published a meta-analysis, an aggregation of existing research. It said that since 1973, the average sperm count among men in Western countries had fallen by 59%, and by somewhat less in the developing world. It seems to have been a well-carried-out study, and it caused quite a stir.

The question, of course, is what caused (or is causing?) this decline. Swan and her co-authors suggested that it is, in large part, the modern chemical industry, and in particular a family of products called “endocrine-disrupting chemicals” (EDCs), which interfere with hormonal processes in the body, especially those involved with development and reproduction. One group of EDCs found in plastics, known as phthalates, are the particular enemy. They get into the water system, they’re in our takeaway containers, they’re in our cosmetics, and they’re damaging our precious bodily fluids. 

Count Down is essentially the book of that study. It expands on the problem, to talk about fertility in general, not just sperm counts; it talks about other causes, like smoking and obesity; and it offers individual advice and policy recommendations for how to ameliorate it. 

All of which probably sounds pretty sensible. Swan thinks we have a growing fertility problem; she thinks she has identified the main cause; and she wants to help solve it.

But the book does not seem sensible. Because for Swan, everything causes fertility problems, not just phthalates. Sugar, beef, cycling, stress, watching TV, doing too much exercise, doing too little, eating the wrong diet; you can barely get out of bed in the morning without sabotaging your chance of having a baby. Undergoing stress and trauma will not only make you less fertile, they’ll affect your children’s fertility (should you remain capable of having them). You ought to “ban plastic from your microwave” and throw out your non-stick pans because they’re killing your sperm. I half expected her to say we ought to wear ray-shielded underpants.

And phthalates and other EDCs don’t just damage your chance of having a baby – they seem to be the cause of everything wrong in the world. Declining bird and fish populations. Abnormal development in alligators and sea snails. Reproductive failure in dolphins and grey seals. The apparent worldwide decline in insect populations is, for Swan, the fault of chemical pollution. She even suggests that the growth in intersex conditions and perhaps the rise of gender dysphoria, and even changes in gender identity, could be because of EDCs (and taking paracetamol in pregnancy!). She does say, in what feels a bit like an act of arse-covering, that it has led us to become more open-minded towards gender expression, which is a “silver lining”.

What’s more, she hints, it’s causing the worldwide slowdown in human reproduction. The world’s “fertility rate” has dropped, she says; halved, in fact. And “the average twenty-something Danish woman today is less fertile than her grandmother was at thirty-five”.

And — and this is the big one — this could literally drive humans extinct. Our sperm could wither and die; we will become unable to have children. She refers several times to Children of Men and The Handmaid’s Tale, even saying that modern gestational surrogacy is a “consensual version of the [Handmaid] scenario”. (I feel like the non-consensual nature of the Handmaid scenario was fairly central to the story, whatever your opinions about surrogacy, but that’s by the bye.)

I can’t confirm all these different claims1, and perhaps many of them are entirely true; it is hardly as though chemical pollution hasn’t caused many environmental catastrophes in the past. Leaded petrol and asbestos are two obvious candidates that took decades to be fixed. And a few quick glances do suggest that there is something real here: EDCs seem to be implicated in the collapse of bald eagle populations, and in an apparent rise in intersex conditions, for instance.

But some parts seem on shakier ground. As it happens I’ve been speaking to entomologists recently for some other work. They thought that insect populations probably were declining (although the data was shaky), some much more than others; and they thought that pesticide pollution was probably a driver, and many pesticides are indeed EDCs. But they also mentioned climate change, eutrophication, light pollution, invasive species, habitat loss. Swan doesn’t outright say that EDCs are the main cause of insect loss (or of declining seabird populations), but she certainly implies it.

There’s also the fact that, as she says, smoking in pregnancy seems to be a huge cause of infertility in male offspring, but expectant mothers smoke much less now than they did even 15 years ago and that is dropping all the time. You’d hope that would go a long way to offsetting environmental influences.

And her take on the human fertility issue just seems entirely backwards to me. The Danish woman being less fertile than her grandmother sounds dreadful, until you realise that fertility is literally measured by how many children you have. The Danish study found that 20-somethings in the 2000s have fewer children than 35-year-olds in the early 1900s. But that’s because Danish women, like women almost everywhere in the world and especially the developed West, are just having fewer children and having them later. The study had nothing to say about whether these women (or their partners) were less capable of having children.

In fact, the decline in total fertility rate – that is, the number of children born per woman — has indeed been going down worldwide; from more than five in 1950 to less than 2.5 last year. But usually I see that portrayed as a good thing. As Swan acknowledges, it correlates with, and is normally said to be partly driven by, female education: the more years of schooling women get in a country, the fewer children the average woman has. 

Fertility also correlates with child mortality: as the number of children dying in childhood goes down, so does the number of children born. There’s also the fact that women still tend to have more, rather than fewer, children than they would ideally like (although I should admit that the data all comes from poorer countries, which have more children and which are less affected by sperm-count decline). That doesn’t mean there isn’t a fertility problem, but it does suggest it’s hardly time to start making comparisons with Children of Men.

Swan says that this reduction in global birth rates will lead to a “demographic crisis”, and she’s probably right: having lots of old people and fewer young, working people will make it harder to support pension schemes, raise taxes, and so on. But unless you want to keep growing the population forever, you’re going to have to go through it at some point. More important, whether it’s good or bad, I don’t think you can reasonably blame it on phthalates or EDCs. You could easily convince me that there is a growing problem of infertility in the developed world, but I doubt it’s the main cause of declining family size, or that it’s mainly caused by EDCs, given the tendency to have children later.

Most important, though, it seems bizarre to suggest that this is going to lead to human extinction. This isn’t me over-interpreting Swan: she really drums it home. Scientists suggest, she says, that fertility decline “could threaten the survival of the human race”; she quotes a researcher saying it is “possible” it could lead to “extinction of the human species”. Her last chapter ends with the phrase “we and other species could end up marching toward the brink of extinction”.

And she says that humanity should be considered an “endangered species”, by the US Fish and Wildlife Service’s definition of the term: “Of five possible criteria for what makes a species endangered, only one needs to be met; the current state of affairs for humans meets at least three.” (Those three criteria are destruction of habitat, inadequate regulatory mechanisms, and man-made factors affecting our existence.)

But there are at least 7.7 billion of us. Our population has increased by more than 10% in the 10 years since I wrote this. You can argue about whether or not we’re damaging our habitat or inadequately regulating ourselves, but surely the key criterion for whether a species is endangered must be that there aren’t very many of them.

Sure, Swan might reply, but the main reason the population is still going up is because we’re living longer. If the world fertility rate drops below replacement, then the population will decline, and eventually we’ll run out of people.

But that is, still, obviously nonsense. We’ve all learned about R in the last year. Of a virus, it’s the average number of new infections that one infected person will cause. If R>1, exponential growth and epidemic; if R<1, disease dies away. But it can apply to anything that reproduces itself: yawns, computer viruses, internet memes. Or humans.

A fertility rate of 2 would be an R of 1 (two people creating two new people), if we ignore deaths in childhood for now. So if the world’s fertility rate dropped below 2, the population of the world will indeed decline, just as the virus does.

But there are different strains of the virus, some of them more infectious — with a higher R — than others. They spread more easily. So the more infectious ones become more common in the population, and even if the “average” virus has an R below 1, it only takes one strain with an R above 1 to eventually become the dominant version and then cause a new wave of the epidemic.

Similarly, there are different fertility rates around the world. Even if R is below one, on average, worldwide, some countries will have higher rates of reproduction. Unless the phthalates are literally rendering us all infertile, which so far they don’t seem to be doing, then humans will continue to reproduce, and those human groups which have the most children will end up being the most common. The future is Amish!

(Plus, if we really do get a Children of Men situation, total global infertility, then efforts to create viable gametes from somatic cells will be increased pretty damn quick; they’re almost there now. We may go extinct some day, but it won’t be fertility loss that does it.)

This hyperventilating about human extinction, and rolling everything bad into a ball labelled “fertility and phthalates”, makes no sense if you think Swan (a respected epidemiologist) is trying to give a dispassionate assessment of fertility issues. But she’s not. This is a polemic. Swan thinks the world doesn’t pay enough attention to the problems of EDC-influenced fertility loss and environmental damage: so she’s upping the stakes as much as she can, making it as big a deal as she can, trying to shift the dial a little bit. The fallacy of reversed moderation declares that you can only do so by dedicating your whole being to the problem (and perhaps overstating it here and there) and looking like a crank.

In a way, I hope she’s right, and that phthalates and other EDCs really are as big a problem as she says. If they are, then — just as we did with leaded petrol, asbestos and CFCs — it is possible that we could simply ban them, find some non-harmful replacement, and watch our alligator, dolphin and sperm populations spring back (although she does point out that the chemical industry, when some harmful chemical is banned, often replaces it with some not-banned but equally harmful equivalent). If all these problems are actually caused a huge, interwoven web of habitat loss, overfishing, air pollution, climate change, diet, and EDCs, then while getting rid of EDCs will help, we’ll still be staring at a severely depleted, damaged world with a lot of complicated problems to fix.

And in one important sense, her book is a success. I’m not going to follow all the advice in her book and replace my shower curtain or my pans — the convenience of non-stick pans seem to me to be worth it for a presumably small risk of reduced fertility (if it weren’t small, we’d have noticed it).

But I am going to turn the little dial in my head, the one labelled “Importance of endocrine-disrupting chemicals”. She has convinced me that they may be a real problem, and I hope someone more dispassionate and less polemical takes a long look at the risks (and benefits) to humanity of using them, and decides whether and where they are worth it. I’m still going to use Tupperware in the microwave, though. 

FOOTNOTES
  1. Not least because there aren’t any footnotes, just a list of references for each chapter, which makes it bloody hard to check. Authors, please use footnotes, they don’t “break up the flow” or anything and it means pedants like me can have a look at your sources.

Tom Chivers is a science writer. His second book, How to Read Numbers, is out now.

TomChivers

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Daniel Björkman
Daniel Björkman
3 years ago

Swan says that this reduction in global birth rates will lead to a “demographic crisis”, and she’s probably right: having lots of old people and fewer young, working people will make it harder to support pension schemes, raise taxes, and so on. But unless you want to keep growing the population forever, you’re going to have to go through it at some point.

Yes. Thank you. That’s a point that keeps getting missed by people panicking over how we’re not pushing out as many babies anymore. Yes, there will be some aches and pains as we readjust from having an ever-growing population, but those are aches and pains that we cannot possibly avoid in the long term. Sooner or later, we’re going to have to get used to each generation no longer being larger than the last, and it might as well be now when we still have some living space left.

Alex Lekas
Alex Lekas
3 years ago

it remains a subject of great fascination that those who complain about ever-dwindling space are here, taking advantage of it, with no plans to leave. It’s almost as interesting as the people who don’t want kids but tend to believe in “free” this or that, as if those services fund themselves.

Ferrusian Gambit
Ferrusian Gambit
3 years ago
Reply to  Alex Lekas

Equally it is a subject of great fascination how people can fail to understand the basic biology of carrying capacity, the well attested Malthusian selective pressure (oh I already here the chattering of ‘but Malthus was wrong because he didn’t predict Fritz-Haber inventing a way to artificially increase the human population for a century of two’) throughout evolution and the basic chemical inputs/outputs to resources that feed agriculture.
As William Hamilton pointed out, the religious morality about this is far crueller than a clear-eyed understanding of the biology of life and evolution. The Christian attitude that ‘all life is equal and valuable’ causes great cruelty in the long run, and modern medicine permitting women to have many children with caesarians meaning that there is no evolution pressure towards successful natural births. It is the attitude that doesn’t permit editing our genes or even passively selecting against harmful genes but just letting rampant bad mutations and recessive genes become an uncontrollable problem. He was quite clear it was just a matter of time until civilisation collapses, one way or another, and allowing so much of the population spread these deleterious genes (both obvious and not so obviously) with no plans to *ethically* reduce their scope and impact so as to reduce human suffering both now and in the future. The moral turpitude of the Nazis and what they did is used as an excuse to ignore basic biology, and whilst the right complain (correctly) about the left ignoring the science of gender, on this issue much of the conservative right deliberately turns a blind eye. And for what it is worth, despite religious slandering the Nazi’s terrible actions were not based principally on modern scientific understanding (which they had little time for outside engineering) but a salmagundi of simplistic Spencerian social Darwinism, nonsense racialist science and Nordic mythology about PIE etc. and which didn’t seek solutions compatible with modern society’s concept of the dignity of human consciousness which *is* possible with modern technology. The equation of compassionate long term reduction in the suffering caused by chronic inherited diseases and ailments with some kind of brutal Nazi T4 extermination program is one of the most sickening lies of the religious mindset. Yet if we let things go on we will end up in a situation where all such pieties will be tossed aside in a brutal struggle for existence. But we seem to prefer blindly trusting in the good will of bronze age mythical deities, storing up a great bottle of horror that is going to explode in our faces.
As a consequence I am actually not sure controlling fertility either way is going to work, as humans have too many mental biases to let humane and scientific solutions play out. I am resigned to the fact that with time nature will take its course and reducing the human population back to a sensible size catastrophically.
But never mind, I am sure the magic man in the sky will rescue us all before this happens.

Last edited 3 years ago by Ferrusian Gambit
Aaron Kevali
Aaron Kevali
3 years ago

At our church (traditional Catholic, Latin Mass, children are seen as a blessing from God) we have no such fertility problems at all. Children are everywhere and families routinely have 3-6 children. And most of our couples, including myself, married in the late twenties, so it’s not just a matter of starting earlier. I think the phthalates might just play a role in the bigger picture, but the main reason fertility is declining is that people don’t want more children. People use contraception, simple.

Alison Houston
Alison Houston
3 years ago
Reply to  Aaron Kevali

Yes, religiosity is excellent for fertility. Belief in God gives sperm the power to reinvigorate themselves. It is only atheist liberals, whose children are always vile anyway, if they manage to produce any, whose sperm suffer from environmental pollution.

Keep up the good work, even though you’re a Catholic, and make sure you teach your children to sing ‘every sperm is sacred’.

Ferrusian Gambit
Ferrusian Gambit
3 years ago
Reply to  Alison Houston

Who would have thought that Northern Ireland’s downfall was predicted by Monty Python.

Last edited 3 years ago by Ferrusian Gambit
Mangle Tangle
Mangle Tangle
3 years ago
Reply to  Alison Houston

That’s a pretty cheap shot at a sincere and well-meaning comment by Aaron. I’m sure it made your day.

David Morley
David Morley
3 years ago
Reply to  Aaron Kevali

I thought it was the meek who were supposed to inherit the Earth, not the religiously virile.

Ferrusian Gambit
Ferrusian Gambit
3 years ago
Reply to  David Morley

It is true that the religious breed fast, but I’m not sure why they should be so proud of that. So do rats. High breeding weaker animals to be exploited as prey by the slower breeding but more powerful carnivorous apex predators.

Last edited 3 years ago by Ferrusian Gambit
Ethniciodo Rodenydo
Ethniciodo Rodenydo
3 years ago
Reply to  Aaron Kevali

Latin Mass! Where is your church

Prana
Prana
3 years ago

So Tom Chivers has realised we may have a problem with EDCs – yet he will still use Tupperware in the microwave and toxic cooking pans. For a science writer, I’m surprised he isn’t also aware of EDCs impact on hormonal cancers [e.g. breast and prostate]. Let’s live passionately whilst we have this glorious life, which is inherently full of risk. But why expose yourself to the risk of a known carcinogen when there are simple alternatives? From an environmental perspective, using less plastic is a positive thing too.

David Morley
David Morley
3 years ago
Reply to  Prana

Yes – what we really need is a guide to which things have the biggest effect. That way we can make some balanced choices.

matti.h.virtanen
matti.h.virtanen
3 years ago

Thanks for a fair review. Concerning sperm counts, there is one variable that seldom even gets a mention: the average frequency of ejaculations in the population donating sperm for these studies. Since masturbation has not been a “sin” for several decades and pornograpy is ridiculously easily available, one would presume that the number of sperm cells in an average “shot” is lower than before, even if the sperm production over a week or a month has not changed. How is this behavioural revolution controlled for in the studies?

Alison Houston
Alison Houston
3 years ago

When they are recruiting subjects they specify ‘w*nkers need not apply’.

Jon Redman
Jon Redman
3 years ago
Reply to  Alison Houston

Surely those are the only people who would apply. I mean how else are they going to come* up with a sample?
* see what I did there?

Last edited 3 years ago by Jon Redman
matti.h.virtanen
matti.h.virtanen
3 years ago
Reply to  Alison Houston

Ha ha. But in case you were serious: all men are w*…

David Morley
David Morley
3 years ago

Probably a good point. Unless, of course, frequency of use stimulates greater production. Does anybody know?

CYRIL NAMMOCK
CYRIL NAMMOCK
3 years ago
Reply to  David Morley

Masturbation increases sperm turnover and keeps the ejaculate fresher and more efficacious. Evolutionary selection pressure.

Last edited 3 years ago by CYRIL NAMMOCK
Ian Perkins
Ian Perkins
3 years ago

Onanism features in the Bible.

Jon Redman
Jon Redman
3 years ago
Reply to  Ian Perkins

Not quite. Onan was, at God’s instruction, shtupping his recently-deceased brother’s widow so she’d have a kid that could be passed off as the brother’s.
God wanted this so as to diddle the inheritance tax laws. Provided he got after it promptly enough, Onan’s child by his sister-in-law would be taken for his brother’s issue, and thus would inherit his brother’s wedge. Onan worked out, however, that no issue = Onan would get the wedge.
Faced with the obvious conflict of interest, Onan solved it in a really ingenious way. He did literally what God commanded, i.e. he lay with his sister-in-law, but to thwart God’s attempted inheritance fiddle, he whipped it out at the vinegar strokes and cast his seed upon the ground.
As a result, God didn’t get His way. An outwitted and annoyed God duly killed Onan.
At no point did Onan arrange a date with Mrs Thumb and her four lovely daughters. He practised withdrawal. It is far from clear whether God killed Onan for whipping it out at the last minute or, more likely, in a general way for having thwarted His will. Presumably, if Onan had declined to do the dirty deed unto his brother’s wife eg because he didn’t fancy her enough, God would have killed him just the same.
The supposition that God disapproves of recreational orgasms that cannot lead to pregnancy is based on nothing in the Bible, and entirely on mediaeval clerics claiming that He did. The claim relies on nobody reading the actual text closely enough to cop on to this which, when it was written in Latin, was easily arranged.
As a result Onan has achieved immortality, like Caesar, Hoover and Boycott, in having his name enter the language, but on mistaken grounds.
Had Onan lived today, he’d no doubt have cast his seed all over his sister-in-law’s face rather than the ground, and then uploaded the footage to xHamster. God would have killed him just the same, but the Church would surely have struggled to misrepresent that as jerking off, faced with the iPhone evidence to the contrary.

Last edited 3 years ago by Jon Redman
David Wrathall
David Wrathall
3 years ago
Reply to  Jon Redman

Wonderful

Jon Redman
Jon Redman
3 years ago
Reply to  David Wrathall

It gets better. Onan’s brother’s name was Er. So presumably, he and his wife each referred to the other as “Er indoors”.

Ferrusian Gambit
Ferrusian Gambit
3 years ago
Reply to  Jon Redman

I am not sure it is as late as medieval clerics, it goes back to St. Augustine and his theories of concupiscence at the very least, if not earlier.
Also the modern obsession with masturbation isn’t really related to abstruse theology like this and far more because of 19th century medical theories which had a tint of religious opprobrium for sure, but passed themselves off as good medical science. (See Kellogg’s, yes he of cereal fame special spas with treatments to prevent self abuse),

Last edited 3 years ago by Ferrusian Gambit
Scott Carson
Scott Carson
3 years ago
Reply to  Jon Redman

More tea, Vicar?

Athena Jones
Athena Jones
3 years ago

Perhaps the biggest factor in increased infertility in males and females is the contraceptive pill.No female was ever meant to have fertility prevented by synthetic hormones for most of her menstrual life and no male was ever meant to be subjected to the massive levels of such synthetic hormones finding their way into the environment and food chain.
Doctors have long known the contraceptive pill predisposed females to Cancer, and yes, they have tweaked things but still remain largely ignorant about reproductive and biological function in humans in general and females in particular.
Yes, plastics and chemicals are a problem, but perhaps the biggest source of poison for the planet and its people is the ever-increasing and massive level of waste from medications, processed by human bodies and then released into the environment. And worse because so much of it is completely unnecessary.
We drown in drugs and antibiotics, prescribed in the name of maybe medicine for diseases and infections people do not have and may never get. With many people taking a couple of drugs for something or another every day from the age of forty, if not younger, and billions of women taking the contraceptive pill, not to mention the antibiotics doled out like lollies by doctors, dentists and the agricultural industry, we can only be in awe of the remarkable resilience of the human organism and this planet. So far anyway.

Last edited 3 years ago by Athena Jones
David Morley
David Morley
3 years ago

In 2017, Swan, along with other scientists, published a meta-analysis, an aggregation of existing research. It said that since 1973, the average sperm count among men in Western countries had fallen by 59%, and by somewhat less in the developing world.

There’s an awful lot in this article that drifts away from the above. For example, shifting the main focus from sperm counts to fertility – where the facts are less clear.
But if something is really going on that can have that big an effect on sperm then we really need to know about it. We know that men with low sperm counts struggle to produce children, so there will be some point at which fertility is affected.
If the above research finding is accurate then there is already enough to worry about.

rickytick66
rickytick66
3 years ago

200,000 abortions a year in the UK, easy access to birth control.

Ars Hendrik
Ars Hendrik
3 years ago
Reply to  rickytick66

Good point. There is a real reluctance to factor in abortion to any discussion of declining birthrates and corresponding declining support ratios. But surely culling upwards of 20% of conceptions before birth has had a severe effect on population levels and demographics.

Hardee Hodges
Hardee Hodges
3 years ago

No idea about sperm counts, what is obvious is that rich people avoid children. As societies get richer then tend not to have children. That started before plastics. And many in repressive nations avoid children as well; again a trend before plastics. But the world population continues to grow anyway, alas for those that constantly worry about feeding them. Maybe climate change will stop these births.

Mike H
Mike H
3 years ago

A brilliant takedown and very useful review. It’s so good to see clear-eyed skepticism of the latest ‘expert’ research in Unherd. It’s rare for journalists to really read scientific claims carefully and think them through but I’d happily pay an entire second subscription for a magazine that just filtered through hyped research findings to get at the truth.
This paragraph jumped out:

This hyperventilating about human extinction … makes no sense if you think Swan (a respected epidemiologist) is trying to give a dispassionate assessment …. But she’s not.

Respected by who, I wonder? Are any epidemiologists respected by anyone by this point? Hyperventilating about human extinction in what looks superficially like science but is actually a mess of invalid assumptions and deceptive definitions is exactly what I’d expect from an epidemiologist. Defining fertility as raw number of babies is especially egregious, that’s not at all what the word means in English, but this is the profession that has no difficulty with defining a COVID death as “any death for any reason whatsoever within 28 days of a positive test”, so who’s really surprised.