Are people masturbating more these days? Or more precisely: are men ejaculating more frequently these days? I feel like there must be some data on this. It's not immediately obvious to me that the increased availability of porn necessarily makes it so.
Prediction #2 assumes reproduction works exactly the same in twenty years/has the same biological limitations. Totally putting aside various 'other' timeline-related concerns people have been animated about lately, this is a longer timeline than many reasonable-enough predictions for when human in vitro gametogenesis is 'viable enough', which would radically change the context of that and other problems.
I had the good fortune to be in a room with fertility doctors not long ago, and here a few random takes:
- fertility almost always an egg problem, not a sperm problem - plenty enough sperm left for fertility at this point
- declining counts may or may not be real, but they tend to argue against it. Why, because sperm count varies a lot from day to day. Personally this make me inclined to believe that masturbation frequency / "porn addiction" may have more to do with it than medical reality
- vitamin D is a very real factor in egg quality. Egg quality can be shown to relate to the amount of body coverage in Middle Eastern women (!!) and current egg quality in 25 year olds in the middle East is more like what used to be seen in typical 40 year olds. Indoor life with a/c and body covering to blame. What does that mean for sperm, well, not so outlandish that similar factors may be at work.
- increasingly off topic, overall fertility: once again Middle Easterners these days seem to get married (often arranged) and then head straight to the IVF center. No one even tries to have sex anymore.
Porn might affect sperm counts but not fertility rates -- since couples who are trying hard to conceive might be foregoing porn in favor of the real thing.
What happens if you change X axis to study quality instead of year, and Y axis to difference in count from comparison cohort?
Have someone neutral grade each study by quality, and see if there’s correlation to claim and effect. If the poorer the study, the bigger change in sperm count is found, that might indicate bias , likely unintentional.
Are there studies about the amount if sperm ‘wasted’ vs ‘deposited’ into proper receptacles?
Will there be studies on ‘the size of the woman’s vagina’ or ‘the desiring affect women have on men’? These might have affect on the amount of sperm a man produces/ejaculates.
> It feels wrong to me to model this linearly, although I can’t explain exactly why besides “it means sperm will reach precisely 0 in thirty years, which is surely false”.
How about "it means sperm counts will be negative after thirty years, which is surely false"?
Obesity could be causing a decline in sperm count, but a decline in sperm count (well, testosterone) could also be causing some amount of obesity. Lower T -> harder to build muscle mass -> less calories being burned at rest.
Lea, R., Byers, A., Sumner, R. et al. Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism. Sci Rep 6, 31281 (2016). https://doi.org/10.1038/srep31281
I think you underweight how likely this is to be the result of decreased censure of porn/masturbation. Go back 30-40 years and lots of people still felt vaguely guilty about masturbating (even if intellectually u think it's ok feeling guilty and sad can be a buzz kill).
Yes, the doctors tell you to abstain but I can't even always remember to fast the day before my physical so ofc some of the subjects forget.
When I was younger I tried to donate sperm (liked idea of someone using it and could get some money) and I certainly forgot to refrain from masturbating for those days (ended up rejected bc not enough sperm)
And if you forget you won't want to sound like someone who couldn't even refrain from masturbating. I sure as hell didn't mention it when I came in. And how good is the evidence the effect is literally zero for everyone if you wait a few days?
--
And re: porn it's not that it's all porn addicts or something but I know ppl who think nothing of opening up porntube for a quick walk whenever they are having trouble falling asleep. Back in the day that would have been more work and probably less likely to be something so casual.
> Partly because the decline could stop - either because we identify the cause and correct it, or for more mysterious reasons. But partly it’s just an unjustifiable penalty for something that it seems very hard to imagine happening.
And partly it is a justified penalty for the most likely outcome being «be us damned if we have any idea either way, given all the confounders we had not even considered recording ten years ago»
Porn might not affect sperm count, but I wonder if it explains the recorded rise in erectile dysfunction and decline in sex frequency among young men. Seems like a plausible hypothesis, but the only study I found seems to debunk it.
Even if we don't correct it, I think most potential causes listed there would level off (e.g. we're using more plastics than fifty years ago, but I don't think the rate of plastics use is still increasing), so if the problem is caused by one of the listed explanations we should be fine.
(Unless it's the porn one and AI-generated superporn makes it worse, I guess)
I should probably say here that before this blog post, I had thought this issue - that sperm counts had been declining - was, as a simple fact, completely uncontested, with no serious counterarguments even presented against this basic thesis. I've seen comments like "Sure, they're declining, but this is not a serious problem" or "Sure, they're declining, but why panic about it? Too many babies anyway" and so on, but this was probably the first thing I've seen that indicated they might *not* be declining, actually.
Is this just discussed differently in Finland and Finnish media than elsewhere?
This was a great article! Now something I've been wondering about is the supposed decline in testosterone over time in healthy adults. Do you guys think this trend is real? I haven't done much research, just read a few abstracts, wondering if anyone has gone through the literature.
If these studies aren't controlling for age wouldn't aging populations, and later age having children, explain it fairly well? That would for why developing countries and China seem to have it worst.
Is this even a problem? As is hinted in the article human males overproduce sperms on a massive scale, probably a legacy from more polyandrous times when males were actually competing sperm to sperm. Anyway, the bottomline is that lower sperm count, if it is even real, should not translate into a general fertility problem until it gets way worse than today. The fact that this rather obscure subject is so popular in the news media probably has more to do with fragile male egos than actual science. (It is still a good thing of Scott to sort it out, of couse.)
You don't mention it, but there's supporting evidence. Not only are sperm counts going down, so is testosterone, and these are obviously related. Next up, rates of testicular cancer are increasing. And surveys show that masculinity is decreasing. These all fit together, and it seems difficult to not posit a general common cause or set of causes. I would guess improved clothing and heating is a major player and the causal evidence for heat stress to sperm quality is strong. As in, they literally put monkeys in hot baths and checked their sperm quality.
The biggest threat to this civilization can be expressed in this equation:
violent men + knowledge explosion = game over
It would be great if we could keep the many peaceful men while getting rid of the minority of violent men, but no society in history has figured out how to do that. Thus, the best thing that could happen to this planet could be a world without men, that is, without male humans.
Or far fewer men at least. A tiny number of men can impregnate huge numbers of women, and would be happy to do so. Or, science is learning how to make sex cells from skin cells. Works in mice, but not yet in humans. Point being, we can maintain the species with far fewer men, or at some point, no men.
Violent men are responsible for 90%+ or more of the violence which so afflicts many millions of innocents all over the planet. It's an unspeakable horror show. In addition, they are a HUGE expense. Removing them from the population would solve a great many very important problems, save this civilization from collapse, and lead to a state of affairs which can reasonably be labeled world peace.
I'm making this argument in some detail in 13 pages of analysis here:
1) In the 21st century face a choice between the knowledge explosion and violent men.
2) We can have either, but not both.
3) If we don't solve this problem, there's not really a point in discussing much else, as we're racing towards a cliff. So, forget about AI, curing cancer, progress in general, the NFL, the Internet, and whatever else matters to you, because if we don't get rid of violent men, sooner or later they will erase it all.
4) If we do get rid of violent men, we can have world peace, the next miracle in human evolution.
Even assuming environmental pressures are driving this, there's such a straightforward evolution mechanism to counteract it that "sperm count goes to zero" strikes me as extremely unlikely.
Surprised there was no mention (that I can see) of the world becoming more peaceful since WWII, especially in daily interactions, probably in part by the removal of high-testosterone men into prisons. (This presupposes that high testosterone is correlated with both higher sperm counts and higher violent tendencies, which quick research indicates that it is.) Norms have changed significantly over these 70 years, removing high-T guys into prisons, or self-segregating them into violent sports. The decline in everyday violence (eg bar fights) also creates an environment whose cues, to the extent they influence T production, are more relaxing, so whatever the environmental contribution to T is should have declined.
Obv this is a hypothesis (or two hypothesis with a link) and empirical studies are needed, but I hesitate to suggest any; the sheer number of countries/regions, over time, over norms, creates too many confounders for me.
How many of these potential causes point to continued decline? E.g. it seems like plastics and pesticides have more or less reached market saturation at this point -- will we really see significant further increases in exposure to them going forwards?
"It feels wrong to me to model this linearly, although I can’t explain exactly why besides “it means sperm will reach precisely 0 in thirty years, which is surely false”"
It seems to me that biology generally isn't linear. There are s-curves, there are sudden breaks, and there's random things having an effect.
As for vitamin D, there's more to sunlight. Humans have nitric oxide precursors under the skin that are activated by sunlight. It definitely affects blood pressure, it might affect sperm production.
Speaking to the plastics issue -- seems important to note that at least for the map shown it's measuring plastic waste *emitted to the ocean* per capita.
I've lived for extended periods in both the USA and South America, and it has always felt like if anything I had less contact with plastics in South America than in the USA, but that the disposal of plastic waste in South America was less effective.
It's common to see lots of trash on streets, beaches, etc to an extent that I don't really see in the USA -- I would suggest that it's possible that we have more contact with plastics in the USA but they are disposed of in such a way that less of it ends up in the ocean.
Admittedly i have no data to support this apart from my own observation and vibes
If you are familiar with the curve of population against time in a fixed-resource culture, say, bacterial colonies in a petri dish, you will be familiar with the exponential growth, slowing down as resources dwindle and waste-products accumulate, eventually leading to a slight reduction in population then a catastrophic crash. Well, what would that look like if we consider ourselves in the situation of those bacteria? We know that over-crowding and stress cause a rise in non-functional behaviours (self-injury, homosexuality - no offense to gay people who were always that way!, paraphilias, aggressive behaviours etc) in both animal populations (eg pigs in a factory farm) or humans in an artificial environment such as a crowded prison. Stressful overcrowding is, I'm sure I have been taught somewhere, a cause of low sperm counts (unless, oddly, you are overcrowded among men alone, in which case elevated testosterone accounts for rises in aggression and sperm counts).
Seen in that light, perhaps some of the odd behaviours we see, especially those that prevent reproduction - asexuality, transgenderism, homosexuality, bizarre genders - might fit in with where we are on that curve. Likewise, we delay having children and have fewer of them as economic conditions get harsher. Now we can add a falling sperm count to the list of physiological ways we unconsciously try to stave off the collapse. We may be at the stage of population contraction and perhaps these are parts of the mechanism.
I've observed a number of morphological differences between the older generations and modern generations; modern generations have smaller and more delicate hands, for example, as a result of the fact that we're (collectively, on average) not smashing and vibrating the shit out of ours hands on a regular basis as much.
Even if sperm count is decreasing, it isn't obvious to me that this necessarily represents a decrease from a "correct" number of sperm. It could simply be that people are less exposed to environmental conditions that were previously increasing the number of sperm.
For example, as I understand it, selenium, which may increase sperm count, used to be a major pollutant in our waterways, but we've greatly improved our treatment of wastewater to eliminate this pollutant - and over the past couple of decades, selenium deficiencies have started to become more prominent an issue; perhaps the odd thing isn't modern sperm levels, but the sperm levels we are attempting to make a comparison to. Mind, it's hard to find exact details, so don't take this as advocacy of this idea, but merely using it as an example of something else that might be confounding our data - we don't know what the "correct" value should be, and things can increase as well as decrease sperm count, so it's entirely possible that the issue is a -decrease- in key pollutants.
An anecdote point: in 1979 (solid date, it was summer after my freshman year in college), I recall an industrial chemist friend of my dad's remarking, "that new-car smell, that's plasticizers, phthalates [he used the word], out-gassing. They're everywhere, if we ever find out they're bad for us, that'll be a big problem".
So, 1979, an industrial chemist in the aerospace industry believed that they were already everywhere, and worried-but-did-not-know if they were bad for us. And also, there may be a difference between "new" (flexible, new-car-smell) plastic and "old" (brittle) plastic in the amount/rate of plasticizers that they leak into the environment.
I'm surprised you seem so skeptical of the obesity explanation. We know obesity rates are going up, and that obesity is associated with reduced sperm counts, so wouldn't it be pretty surprising if rising obesity weren't causing at least some of the decrease? (even if obesity being the only cause doesn't perfectly match the noisy regional variation).
It makes me wonder if there might be some cognitive bias in play, favoring exciting solutions (e.g. toxic environmental plastics are endangering us!) over mundane solutions (e.g. obesity is already known to be associated with reduced sperm counts).
At the moment (2/17/2023, 10:22 EST) substack is saying this was posted "11 hr ago", but I thought I saw it (days?) earlier. Is there a glitch in the reported time for posts?
There is at least one dissertation / thesis. prior to 1975 that penis size is decreasing as well, and the proposed cause was pesticides. The author was my favorite Aunt although she left KS abruptly after marrying my uncle. I was told she returned to southern CA. Her name was Joanne (SP?) Gaston or Joanne Gaston-Pressgrove. I have been unable to find her and would ask that if someone is able to find her thesis or any indication of a Berkly grad with a similar name, I would appreciate you sharing any information. Unk passed a few years back and I would really like to let her know. TIA
Actually, the largest contributor - assuming the fall is real - is probably just age.
Look at the sperm count by age decile and compare vs. the average age of the "donors". Increasing life expectancies = older men = older men contributing sperm count numbers.
I am 99% sure sperm counts decline with age, period, and an aging population would certainly yield lower overall sperm counts just because of the aging.
The other things are probably much more minor factors, relatively speaking, but are far more alarmist hence useful to dumbass narratives. See climate change.
"Harvard Gender Science Laboratory paper [...] mostly just says that it sounds sexist to say something bad might be happening to men (it also adds that since some studies have found the decline is higher in Europe, it’s racist for saying something bad is happening to white men)."
I read some of the paper, and the closest I could find to a claim of sexism was a paragraph mentioning that MRAs and Alex Jones have referenced declining sperm counts to complain about soy boys. The main point seems to be that even if sperm counts have declined, it doesn't seem to be pathological, there's no reason to think the levels in the 70s were natural or optimal, and high sperm count is not particularly a marker of general health.
It does use a lot of disapproving air quotes about dividing countries into """Western""" and """Other""" and points out that pollution of plastics and pesticides tends to be worse in poor countries, which doesn't really fit with declining sperm counts in western countries.
I tried to have children with my (now ex-) wife for ±5 years using IVF in France. The cause of infertility was my sperm count being too low (as low as <1m/mL at the worst.) Since I spent plenty of time around doctors and other patients, here are a few points I thought I could share:
- There is a global concensus among professional that the global sperm count is lowering worldwide (they might be biaised since they only see infertile patients though)
- My sperm count varied dramatically (20× factor) over a period of 5 years. Some can be attributed to the surgeries I had, but in between surgeries, I still experienced a 5× change. It didn't seem corelated with any other variable (health, eating habit, alcool consumption or smoking)
- Sperm count is usually corelated with sperm quality. So sperm count and fertility don't have a linear relationship, and it might skew some studies quite a lot:
- Low quality sperm can be very short-lived and when the lab performs a sperm count, they only count the effective sperm found (discarding dead, or imobile ones), making the timing between production and analysis very crucial which it is not.
I made a few samples at home and brought them to the lab for analysis about 30" later. I didn't check at what time they made the count, but I had 30% less than the week before. I paid a little extra for a more in-depth analysis and went to a different lab where I needed to produce the sample there, and they would check periodically over a period of 24h.
Just after producing I had my 30% more, and ~80% were dead (thus not counted) after 24h. The high variability of the result might just be the different collection methods used.
Look I realize a lot of people are putting effort and thought into this hypothesis.
But frankly, I find it crazy to see an idea entirely based upon surveys of non-random, non-representative samples of the population being so widely discussed as though it has solid scientific backing. The media really need to chill on this topic.
These meta analyses are mostly GIGO. The fact that this obvious problem with the data is only listed as limitation #3, and then is so easily dismissed by the authors of these studies, is something of a cosmic joke.
Scott your analysis of the issue was legitimate and helpful to frame the topic.
But you forgot to mention what I see as the most likely possibility: Based upon my observations of other fields of epidemiology that receive far more funding and research interest, I estimate a 90% probability that in 20 years we still will not have any truly useful data to either strongly support or falsify this hypothesis.
Likely instead this will continue to be among the topics to be debated endlessly among friends at a pub while enjoying a flight of good beers…
I'm apparently the top "NO" holder on Manifold, so I suppose I should say something.
My estimate (based solely on this post, and no other research) is about 30% for "In twenty years, will the best evidence available suggest that sperm counts have been substantially declining across most of the world?" That's, roughly, 25% that there is a non-trivial phenomenon (beyond simply "people are getting older", which Scott said doesn't count), and 5% "there is no decline, but the scientific establishment in 20 years is fundamentally broken, probably because of scientists who do bad research to get headlines and/or tenure".
The key is Figure 2, along with "approximately every study makes a ton of compromises for longitudinal data". As other people have mentioned, Garbage In Garbage Out. And "sperm production of a healthy male" (by height? by weight? by mL of seminal fluid?) ... well, maybe it does vary by 50% depending on the population, depending on what metric you are using. Which just means the differences in populations surveyed (which Scott notes) make a simple linear regression problematic.
( there is also my meta-heuristic of "after years of reading this blog, I believe Scott consistently over-estimates the likelihood of phenomena like this being real" )
The proper level of concern should be... I was going to argue zero, but then I found actual data. But the numbers are all over the place in a hard to disentangle way. Seriously, look at this analysis, and tell me the numbers thrown about aren't sometimes contradicting each other, or at the very least difficult to reconcile. Eyeballing it, it seems 2% - 7% of men have defective sperm problems. Of the 200 hundred pronatalist married couples I know, I would say 4 - 7 percent have difficulty conceiving. Maybe half of that is due to male sperm issues. So these percentages strike me as a bit high. Nonetheless, if the percentage were to double, I would start to be very concerned.
If we combine increased male issues with women trying to conceive later in life, we could wind up with a lot of disappointed couples, unable to conceive. Only 12% of the population has a 4 person household. Dropping that percent any lower seems pretty bad for creating a culture where people would want children.
So, while I, started out writing this skeptical that this matters... I am now actually worried about this on some margin. Though, I still think improving sperm count is at best a third tier problem for improving fertility. There are more important levers to pull on that front.
"Given how hard it is to find this effect at all, we should be suspicious that all of these differences are fake, and that actually we don’t know anything about where sperm decline is faster or slower."
I don't understand. From the examples you've given, isn't it obvious that poorer, less privileged people have lower sperm counts than richer, more privileged people?
Maybe it has to do with our current trend of monogamous human relationships. I remember reading that males of ape species that mated with many females had unfeasibly large testicles, whereas those species favouring monogamous parings had smaller testicles. If you're mating with multiple females per day, that favours large, productive testicles but as more humans reproduce monogamously and the mega-shaggers are blocked by birth control, the smaller balled (and watery-seeded) are becoming the norm. Big-balled super-seed-spreaders have lost their evolutionary advantage and their numbers are declining in humans.
Major confounder not discussed- underwear style. It's already known that men who wear cotton boxers have higher sperm counts, and men who wear tighter fitting underwear have lower sperm counts. I recall a few studies saying that men who wear underwear made with more synthetic materials have lower sperm counts, as well, so if that's true(I have only seen twitter screenshots of the conclusions but polyester on your balls reducing fertility seems at least reasonable, if not confirmed) then we have two confounds(change in material used in underwear and change in style of underwear). Even assuming only underwear tightness matters, men- or at least those men who participate in fertility studies- switching from boxers to athletic underwear or boxer briefs would represent a major confound if it happened.
So did any of these studies control for or even document what kind of underwear their participants wore?
I think you're being arbitrarily dismissive of the Harvard paper or their authors.
"mostly written by Gender Studies professors, anthropologists"
Lots of studies in the past have included various biases, for example they made wide claims while only including white men in their data. Of course you don't need to be a gender studies professor to realize this is bad science.
Good science is difficult and anybody has the ability it do it correctly, and it's not meant to be socially or politically motivated. But I think they could be more attuned to these identifying these biases and calling them out.
Methodology should be considered. In the earlier studies, the counts would’ve been done with a calibrated micrometer - just a person at a microscope clicking a counter for each sperm in a little grid. Not super accurate. More recently, I believe there’s image analysis that can count it for you or at least it does some of the heavy lifting. I’m sure this is described in materials and methods of the papers.
What if the sperm count correlates with the social status of the male? It is a heretic thought, but primate reproduction tends to rely on high status males... The sperm count decline might be a consequence of the patriarchy being smashed progressively.
"In conclusion, drinking Coca-Cola and Pepsi-Cola could promote testis development, enhance testosterone secretion, increase serum EGF concentrations, also accelerated expressions of AR protein in the mice testes. Our findings provided the scientific bases and for fully understanding CBs effects and their mechanism on development and reproduction functions of humans, but also benefit to prevent prostate dysfunction and cancer."
Good for male mice, bad for female mice and their reproductive system, though.
I’m curious about evolution. In the past people would have a dozen kids in the hopes that a couple of them would live to procreate, a high sperm count would presumably make conception easier so women would get pregnant faster and have more kids over their lifetime. Now most people only have a couple kids who will almost certainly have a couple kids of their own, and it doesn’t matter if it took and extra year or two for the parents to conceive. The removal of this evolutionary pressure forcing sperm counts up could mean that random mutations which bring it down are no longer being selected against, but there is still some amount of pressure for general fertility which is why the decline is fairly small.
Because the data is contradictory, it's useless. You can't make any useful predictions based on garbage info. This is some sort of astrology tier guesswork.
Drinking water is being delivered by PVC pipes now more than ever. About half the distribution size water pipe in the USA is now PVC. I believe it's the reason for our increase in pancreatic cancer, diabetes, and more. There are dangers in exposure to PVC. Water utilities should not use PVC but should use the time-proven safety of iron pipe.
Are people masturbating more these days? Or more precisely: are men ejaculating more frequently these days? I feel like there must be some data on this. It's not immediately obvious to me that the increased availability of porn necessarily makes it so.
Prediction #2 assumes reproduction works exactly the same in twenty years/has the same biological limitations. Totally putting aside various 'other' timeline-related concerns people have been animated about lately, this is a longer timeline than many reasonable-enough predictions for when human in vitro gametogenesis is 'viable enough', which would radically change the context of that and other problems.
I had the good fortune to be in a room with fertility doctors not long ago, and here a few random takes:
- fertility almost always an egg problem, not a sperm problem - plenty enough sperm left for fertility at this point
- declining counts may or may not be real, but they tend to argue against it. Why, because sperm count varies a lot from day to day. Personally this make me inclined to believe that masturbation frequency / "porn addiction" may have more to do with it than medical reality
- vitamin D is a very real factor in egg quality. Egg quality can be shown to relate to the amount of body coverage in Middle Eastern women (!!) and current egg quality in 25 year olds in the middle East is more like what used to be seen in typical 40 year olds. Indoor life with a/c and body covering to blame. What does that mean for sperm, well, not so outlandish that similar factors may be at work.
- increasingly off topic, overall fertility: once again Middle Easterners these days seem to get married (often arranged) and then head straight to the IVF center. No one even tries to have sex anymore.
YMMV.
Porn might affect sperm counts but not fertility rates -- since couples who are trying hard to conceive might be foregoing porn in favor of the real thing.
What happens if you change X axis to study quality instead of year, and Y axis to difference in count from comparison cohort?
Have someone neutral grade each study by quality, and see if there’s correlation to claim and effect. If the poorer the study, the bigger change in sperm count is found, that might indicate bias , likely unintentional.
What about the similar decline in testosterone?
What about the similar decline in testosterone?
Are there studies about the amount if sperm ‘wasted’ vs ‘deposited’ into proper receptacles?
Will there be studies on ‘the size of the woman’s vagina’ or ‘the desiring affect women have on men’? These might have affect on the amount of sperm a man produces/ejaculates.
> It feels wrong to me to model this linearly, although I can’t explain exactly why besides “it means sperm will reach precisely 0 in thirty years, which is surely false”.
How about "it means sperm counts will be negative after thirty years, which is surely false"?
Obesity could be causing a decline in sperm count, but a decline in sperm count (well, testosterone) could also be causing some amount of obesity. Lower T -> harder to build muscle mass -> less calories being burned at rest.
Lea, R., Byers, A., Sumner, R. et al. Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism. Sci Rep 6, 31281 (2016). https://doi.org/10.1038/srep31281
I think you underweight how likely this is to be the result of decreased censure of porn/masturbation. Go back 30-40 years and lots of people still felt vaguely guilty about masturbating (even if intellectually u think it's ok feeling guilty and sad can be a buzz kill).
Yes, the doctors tell you to abstain but I can't even always remember to fast the day before my physical so ofc some of the subjects forget.
When I was younger I tried to donate sperm (liked idea of someone using it and could get some money) and I certainly forgot to refrain from masturbating for those days (ended up rejected bc not enough sperm)
And if you forget you won't want to sound like someone who couldn't even refrain from masturbating. I sure as hell didn't mention it when I came in. And how good is the evidence the effect is literally zero for everyone if you wait a few days?
--
And re: porn it's not that it's all porn addicts or something but I know ppl who think nothing of opening up porntube for a quick walk whenever they are having trouble falling asleep. Back in the day that would have been more work and probably less likely to be something so casual.
> Partly because the decline could stop - either because we identify the cause and correct it, or for more mysterious reasons. But partly it’s just an unjustifiable penalty for something that it seems very hard to imagine happening.
And partly it is a justified penalty for the most likely outcome being «be us damned if we have any idea either way, given all the confounders we had not even considered recording ten years ago»
Porn might not affect sperm count, but I wonder if it explains the recorded rise in erectile dysfunction and decline in sex frequency among young men. Seems like a plausible hypothesis, but the only study I found seems to debunk it.
https://www.nature.com/articles/s41443-022-00596-y
If the population declines and I believe it is sperm rates will be a small factor in that equation.
Disappointed the "other things" section didn't include "extremely fast evolution".
Even if we don't correct it, I think most potential causes listed there would level off (e.g. we're using more plastics than fifty years ago, but I don't think the rate of plastics use is still increasing), so if the problem is caused by one of the listed explanations we should be fine.
(Unless it's the porn one and AI-generated superporn makes it worse, I guess)
I should probably say here that before this blog post, I had thought this issue - that sperm counts had been declining - was, as a simple fact, completely uncontested, with no serious counterarguments even presented against this basic thesis. I've seen comments like "Sure, they're declining, but this is not a serious problem" or "Sure, they're declining, but why panic about it? Too many babies anyway" and so on, but this was probably the first thing I've seen that indicated they might *not* be declining, actually.
Is this just discussed differently in Finland and Finnish media than elsewhere?
This was a great article! Now something I've been wondering about is the supposed decline in testosterone over time in healthy adults. Do you guys think this trend is real? I haven't done much research, just read a few abstracts, wondering if anyone has gone through the literature.
haven't testosterone levels declined precipitously since then?
If these studies aren't controlling for age wouldn't aging populations, and later age having children, explain it fairly well? That would for why developing countries and China seem to have it worst.
Is this even a problem? As is hinted in the article human males overproduce sperms on a massive scale, probably a legacy from more polyandrous times when males were actually competing sperm to sperm. Anyway, the bottomline is that lower sperm count, if it is even real, should not translate into a general fertility problem until it gets way worse than today. The fact that this rather obscure subject is so popular in the news media probably has more to do with fragile male egos than actual science. (It is still a good thing of Scott to sort it out, of couse.)
You don't mention it, but there's supporting evidence. Not only are sperm counts going down, so is testosterone, and these are obviously related. Next up, rates of testicular cancer are increasing. And surveys show that masculinity is decreasing. These all fit together, and it seems difficult to not posit a general common cause or set of causes. I would guess improved clothing and heating is a major player and the causal evidence for heat stress to sperm quality is strong. As in, they literally put monkeys in hot baths and checked their sperm quality.
https://kirkegaard.substack.com/p/secular-genetic-phenotype-paradoxes
Masculinity surveys, note these are pre-Woke takeover
https://today.yougov.com/topics/society/articles-reports/2016/05/23/decline-manly-man
This could be very good news.
The biggest threat to this civilization can be expressed in this equation:
violent men + knowledge explosion = game over
It would be great if we could keep the many peaceful men while getting rid of the minority of violent men, but no society in history has figured out how to do that. Thus, the best thing that could happen to this planet could be a world without men, that is, without male humans.
Or far fewer men at least. A tiny number of men can impregnate huge numbers of women, and would be happy to do so. Or, science is learning how to make sex cells from skin cells. Works in mice, but not yet in humans. Point being, we can maintain the species with far fewer men, or at some point, no men.
Violent men are responsible for 90%+ or more of the violence which so afflicts many millions of innocents all over the planet. It's an unspeakable horror show. In addition, they are a HUGE expense. Removing them from the population would solve a great many very important problems, save this civilization from collapse, and lead to a state of affairs which can reasonably be labeled world peace.
I'm making this argument in some detail in 13 pages of analysis here:
https://www.tannytalk.com/p/world-peace-table-of-contents
Here's our situation in a nutshell.
1) In the 21st century face a choice between the knowledge explosion and violent men.
2) We can have either, but not both.
3) If we don't solve this problem, there's not really a point in discussing much else, as we're racing towards a cliff. So, forget about AI, curing cancer, progress in general, the NFL, the Internet, and whatever else matters to you, because if we don't get rid of violent men, sooner or later they will erase it all.
4) If we do get rid of violent men, we can have world peace, the next miracle in human evolution.
Declining sperm counts could be very good news.
Even assuming environmental pressures are driving this, there's such a straightforward evolution mechanism to counteract it that "sperm count goes to zero" strikes me as extremely unlikely.
Surprised there was no mention (that I can see) of the world becoming more peaceful since WWII, especially in daily interactions, probably in part by the removal of high-testosterone men into prisons. (This presupposes that high testosterone is correlated with both higher sperm counts and higher violent tendencies, which quick research indicates that it is.) Norms have changed significantly over these 70 years, removing high-T guys into prisons, or self-segregating them into violent sports. The decline in everyday violence (eg bar fights) also creates an environment whose cues, to the extent they influence T production, are more relaxing, so whatever the environmental contribution to T is should have declined.
Obv this is a hypothesis (or two hypothesis with a link) and empirical studies are needed, but I hesitate to suggest any; the sheer number of countries/regions, over time, over norms, creates too many confounders for me.
I would advocate strongly for a "impact of plastics on the human body: much more than you wanted to know" post from our fearless leader.
What does "community-dwelling" mean in this context? Does it mean people who are not institutionalized (i.e. in long-term medical care or prison)?
What a hilarious timing, to publish it one day after the meta-analysis:
"Worldwide Temporal Trends in Penile Length: A Systematic Review and Meta-Analysis"
https://wjmh.org/DOIx.php?id=10.5534/wjmh.220203
(Spoiler: the analysis concludes that the erect penile length increased 24% over the past 29 years.)
How many of these potential causes point to continued decline? E.g. it seems like plastics and pesticides have more or less reached market saturation at this point -- will we really see significant further increases in exposure to them going forwards?
"It feels wrong to me to model this linearly, although I can’t explain exactly why besides “it means sperm will reach precisely 0 in thirty years, which is surely false”"
It seems to me that biology generally isn't linear. There are s-curves, there are sudden breaks, and there's random things having an effect.
As for vitamin D, there's more to sunlight. Humans have nitric oxide precursors under the skin that are activated by sunlight. It definitely affects blood pressure, it might affect sperm production.
Speaking to the plastics issue -- seems important to note that at least for the map shown it's measuring plastic waste *emitted to the ocean* per capita.
I've lived for extended periods in both the USA and South America, and it has always felt like if anything I had less contact with plastics in South America than in the USA, but that the disposal of plastic waste in South America was less effective.
It's common to see lots of trash on streets, beaches, etc to an extent that I don't really see in the USA -- I would suggest that it's possible that we have more contact with plastics in the USA but they are disposed of in such a way that less of it ends up in the ocean.
Admittedly i have no data to support this apart from my own observation and vibes
If you are familiar with the curve of population against time in a fixed-resource culture, say, bacterial colonies in a petri dish, you will be familiar with the exponential growth, slowing down as resources dwindle and waste-products accumulate, eventually leading to a slight reduction in population then a catastrophic crash. Well, what would that look like if we consider ourselves in the situation of those bacteria? We know that over-crowding and stress cause a rise in non-functional behaviours (self-injury, homosexuality - no offense to gay people who were always that way!, paraphilias, aggressive behaviours etc) in both animal populations (eg pigs in a factory farm) or humans in an artificial environment such as a crowded prison. Stressful overcrowding is, I'm sure I have been taught somewhere, a cause of low sperm counts (unless, oddly, you are overcrowded among men alone, in which case elevated testosterone accounts for rises in aggression and sperm counts).
Seen in that light, perhaps some of the odd behaviours we see, especially those that prevent reproduction - asexuality, transgenderism, homosexuality, bizarre genders - might fit in with where we are on that curve. Likewise, we delay having children and have fewer of them as economic conditions get harsher. Now we can add a falling sperm count to the list of physiological ways we unconsciously try to stave off the collapse. We may be at the stage of population contraction and perhaps these are parts of the mechanism.
For people who want to learn more about sperm biology, I wrote this post last year: https://denovo.substack.com/p/know-your-sperm
I don't think fertility will actually decrease due to declining sperm count.
I've observed a number of morphological differences between the older generations and modern generations; modern generations have smaller and more delicate hands, for example, as a result of the fact that we're (collectively, on average) not smashing and vibrating the shit out of ours hands on a regular basis as much.
Even if sperm count is decreasing, it isn't obvious to me that this necessarily represents a decrease from a "correct" number of sperm. It could simply be that people are less exposed to environmental conditions that were previously increasing the number of sperm.
For example, as I understand it, selenium, which may increase sperm count, used to be a major pollutant in our waterways, but we've greatly improved our treatment of wastewater to eliminate this pollutant - and over the past couple of decades, selenium deficiencies have started to become more prominent an issue; perhaps the odd thing isn't modern sperm levels, but the sperm levels we are attempting to make a comparison to. Mind, it's hard to find exact details, so don't take this as advocacy of this idea, but merely using it as an example of something else that might be confounding our data - we don't know what the "correct" value should be, and things can increase as well as decrease sperm count, so it's entirely possible that the issue is a -decrease- in key pollutants.
An anecdote point: in 1979 (solid date, it was summer after my freshman year in college), I recall an industrial chemist friend of my dad's remarking, "that new-car smell, that's plasticizers, phthalates [he used the word], out-gassing. They're everywhere, if we ever find out they're bad for us, that'll be a big problem".
So, 1979, an industrial chemist in the aerospace industry believed that they were already everywhere, and worried-but-did-not-know if they were bad for us. And also, there may be a difference between "new" (flexible, new-car-smell) plastic and "old" (brittle) plastic in the amount/rate of plasticizers that they leak into the environment.
I'm surprised you seem so skeptical of the obesity explanation. We know obesity rates are going up, and that obesity is associated with reduced sperm counts, so wouldn't it be pretty surprising if rising obesity weren't causing at least some of the decrease? (even if obesity being the only cause doesn't perfectly match the noisy regional variation).
It makes me wonder if there might be some cognitive bias in play, favoring exciting solutions (e.g. toxic environmental plastics are endangering us!) over mundane solutions (e.g. obesity is already known to be associated with reduced sperm counts).
At the moment (2/17/2023, 10:22 EST) substack is saying this was posted "11 hr ago", but I thought I saw it (days?) earlier. Is there a glitch in the reported time for posts?
There is at least one dissertation / thesis. prior to 1975 that penis size is decreasing as well, and the proposed cause was pesticides. The author was my favorite Aunt although she left KS abruptly after marrying my uncle. I was told she returned to southern CA. Her name was Joanne (SP?) Gaston or Joanne Gaston-Pressgrove. I have been unable to find her and would ask that if someone is able to find her thesis or any indication of a Berkly grad with a similar name, I would appreciate you sharing any information. Unk passed a few years back and I would really like to let her know. TIA
Actually, the largest contributor - assuming the fall is real - is probably just age.
Look at the sperm count by age decile and compare vs. the average age of the "donors". Increasing life expectancies = older men = older men contributing sperm count numbers.
I am 99% sure sperm counts decline with age, period, and an aging population would certainly yield lower overall sperm counts just because of the aging.
The other things are probably much more minor factors, relatively speaking, but are far more alarmist hence useful to dumbass narratives. See climate change.
While your at it, can we do the declining testosterone levels claim as well? Interesting post!
What about exercise?
"Harvard Gender Science Laboratory paper [...] mostly just says that it sounds sexist to say something bad might be happening to men (it also adds that since some studies have found the decline is higher in Europe, it’s racist for saying something bad is happening to white men)."
I read some of the paper, and the closest I could find to a claim of sexism was a paragraph mentioning that MRAs and Alex Jones have referenced declining sperm counts to complain about soy boys. The main point seems to be that even if sperm counts have declined, it doesn't seem to be pathological, there's no reason to think the levels in the 70s were natural or optimal, and high sperm count is not particularly a marker of general health.
It does use a lot of disapproving air quotes about dividing countries into """Western""" and """Other""" and points out that pollution of plastics and pesticides tends to be worse in poor countries, which doesn't really fit with declining sperm counts in western countries.
Disclaimer: N=1, personal experience, YMMV.
I tried to have children with my (now ex-) wife for ±5 years using IVF in France. The cause of infertility was my sperm count being too low (as low as <1m/mL at the worst.) Since I spent plenty of time around doctors and other patients, here are a few points I thought I could share:
- There is a global concensus among professional that the global sperm count is lowering worldwide (they might be biaised since they only see infertile patients though)
- My sperm count varied dramatically (20× factor) over a period of 5 years. Some can be attributed to the surgeries I had, but in between surgeries, I still experienced a 5× change. It didn't seem corelated with any other variable (health, eating habit, alcool consumption or smoking)
- Sperm count is usually corelated with sperm quality. So sperm count and fertility don't have a linear relationship, and it might skew some studies quite a lot:
- Low quality sperm can be very short-lived and when the lab performs a sperm count, they only count the effective sperm found (discarding dead, or imobile ones), making the timing between production and analysis very crucial which it is not.
I made a few samples at home and brought them to the lab for analysis about 30" later. I didn't check at what time they made the count, but I had 30% less than the week before. I paid a little extra for a more in-depth analysis and went to a different lab where I needed to produce the sample there, and they would check periodically over a period of 24h.
Just after producing I had my 30% more, and ~80% were dead (thus not counted) after 24h. The high variability of the result might just be the different collection methods used.
Look I realize a lot of people are putting effort and thought into this hypothesis.
But frankly, I find it crazy to see an idea entirely based upon surveys of non-random, non-representative samples of the population being so widely discussed as though it has solid scientific backing. The media really need to chill on this topic.
These meta analyses are mostly GIGO. The fact that this obvious problem with the data is only listed as limitation #3, and then is so easily dismissed by the authors of these studies, is something of a cosmic joke.
Scott your analysis of the issue was legitimate and helpful to frame the topic.
But you forgot to mention what I see as the most likely possibility: Based upon my observations of other fields of epidemiology that receive far more funding and research interest, I estimate a 90% probability that in 20 years we still will not have any truly useful data to either strongly support or falsify this hypothesis.
Likely instead this will continue to be among the topics to be debated endlessly among friends at a pub while enjoying a flight of good beers…
I'm apparently the top "NO" holder on Manifold, so I suppose I should say something.
My estimate (based solely on this post, and no other research) is about 30% for "In twenty years, will the best evidence available suggest that sperm counts have been substantially declining across most of the world?" That's, roughly, 25% that there is a non-trivial phenomenon (beyond simply "people are getting older", which Scott said doesn't count), and 5% "there is no decline, but the scientific establishment in 20 years is fundamentally broken, probably because of scientists who do bad research to get headlines and/or tenure".
The key is Figure 2, along with "approximately every study makes a ton of compromises for longitudinal data". As other people have mentioned, Garbage In Garbage Out. And "sperm production of a healthy male" (by height? by weight? by mL of seminal fluid?) ... well, maybe it does vary by 50% depending on the population, depending on what metric you are using. Which just means the differences in populations surveyed (which Scott notes) make a simple linear regression problematic.
( there is also my meta-heuristic of "after years of reading this blog, I believe Scott consistently over-estimates the likelihood of phenomena like this being real" )
With any luck.
Somehow people are still arguing over what causes obesity after 40 years. So I’m not holding my breath.
Please also look at testosterone changes over time, it would make sense that this is a causal driver of sperm count.
The proper level of concern should be... I was going to argue zero, but then I found actual data. But the numbers are all over the place in a hard to disentangle way. Seriously, look at this analysis, and tell me the numbers thrown about aren't sometimes contradicting each other, or at the very least difficult to reconcile. Eyeballing it, it seems 2% - 7% of men have defective sperm problems. Of the 200 hundred pronatalist married couples I know, I would say 4 - 7 percent have difficulty conceiving. Maybe half of that is due to male sperm issues. So these percentages strike me as a bit high. Nonetheless, if the percentage were to double, I would start to be very concerned.
If we combine increased male issues with women trying to conceive later in life, we could wind up with a lot of disappointed couples, unable to conceive. Only 12% of the population has a 4 person household. Dropping that percent any lower seems pretty bad for creating a culture where people would want children.
So, while I, started out writing this skeptical that this matters... I am now actually worried about this on some margin. Though, I still think improving sperm count is at best a third tier problem for improving fertility. There are more important levers to pull on that front.
"Given how hard it is to find this effect at all, we should be suspicious that all of these differences are fake, and that actually we don’t know anything about where sperm decline is faster or slower."
I don't understand. From the examples you've given, isn't it obvious that poorer, less privileged people have lower sperm counts than richer, more privileged people?
Anyone know what's up with Data Secrets Lox?
Maybe it has to do with our current trend of monogamous human relationships. I remember reading that males of ape species that mated with many females had unfeasibly large testicles, whereas those species favouring monogamous parings had smaller testicles. If you're mating with multiple females per day, that favours large, productive testicles but as more humans reproduce monogamously and the mega-shaggers are blocked by birth control, the smaller balled (and watery-seeded) are becoming the norm. Big-balled super-seed-spreaders have lost their evolutionary advantage and their numbers are declining in humans.
Epistemic status - hypothèse à la crackpot.
Major confounder not discussed- underwear style. It's already known that men who wear cotton boxers have higher sperm counts, and men who wear tighter fitting underwear have lower sperm counts. I recall a few studies saying that men who wear underwear made with more synthetic materials have lower sperm counts, as well, so if that's true(I have only seen twitter screenshots of the conclusions but polyester on your balls reducing fertility seems at least reasonable, if not confirmed) then we have two confounds(change in material used in underwear and change in style of underwear). Even assuming only underwear tightness matters, men- or at least those men who participate in fertility studies- switching from boxers to athletic underwear or boxer briefs would represent a major confound if it happened.
So did any of these studies control for or even document what kind of underwear their participants wore?
I think you're being arbitrarily dismissive of the Harvard paper or their authors.
"mostly written by Gender Studies professors, anthropologists"
Lots of studies in the past have included various biases, for example they made wide claims while only including white men in their data. Of course you don't need to be a gender studies professor to realize this is bad science.
Good science is difficult and anybody has the ability it do it correctly, and it's not meant to be socially or politically motivated. But I think they could be more attuned to these identifying these biases and calling them out.
Methodology should be considered. In the earlier studies, the counts would’ve been done with a calibrated micrometer - just a person at a microscope clicking a counter for each sperm in a little grid. Not super accurate. More recently, I believe there’s image analysis that can count it for you or at least it does some of the heavy lifting. I’m sure this is described in materials and methods of the papers.
What if the sperm count correlates with the social status of the male? It is a heretic thought, but primate reproduction tends to rely on high status males... The sperm count decline might be a consequence of the patriarchy being smashed progressively.
A possible solution? I was directed to this by the good people over at r/Drama:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9867816/
"In conclusion, drinking Coca-Cola and Pepsi-Cola could promote testis development, enhance testosterone secretion, increase serum EGF concentrations, also accelerated expressions of AR protein in the mice testes. Our findings provided the scientific bases and for fully understanding CBs effects and their mechanism on development and reproduction functions of humans, but also benefit to prevent prostate dysfunction and cancer."
Good for male mice, bad for female mice and their reproductive system, though.
I’m curious about evolution. In the past people would have a dozen kids in the hopes that a couple of them would live to procreate, a high sperm count would presumably make conception easier so women would get pregnant faster and have more kids over their lifetime. Now most people only have a couple kids who will almost certainly have a couple kids of their own, and it doesn’t matter if it took and extra year or two for the parents to conceive. The removal of this evolutionary pressure forcing sperm counts up could mean that random mutations which bring it down are no longer being selected against, but there is still some amount of pressure for general fertility which is why the decline is fairly small.
You should do a "Testosterone MMTYWTK"
Because the data is contradictory, it's useless. You can't make any useful predictions based on garbage info. This is some sort of astrology tier guesswork.
My guess is that it's due to stress. Richer people are less stressed out, so have had a smaller decline.
Drinking water is being delivered by PVC pipes now more than ever. About half the distribution size water pipe in the USA is now PVC. I believe it's the reason for our increase in pancreatic cancer, diabetes, and more. There are dangers in exposure to PVC. Water utilities should not use PVC but should use the time-proven safety of iron pipe.