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Comment by chaostheory | Hacker News Reader

The issue is that male fertility and testosterone keeps falling consecutively every year in developed countries. We don’t know why. If I were to guesss, it’s due to the use of plastics with our food. Even without extremes of temperature, research has found that plastic will leech synthetic hormones like BPA (synthetic estrogen) and BPS. This is making its way into almost all of our food and drink

On the bright side, the threat of overpopulation is lessened

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The vast majority of fertile-age, opposite-sex couples can conceive fairly quickly if they try, and people in the upper half of the global income distribution now have access to medical care if they run into any issues. Infant mortality is also way down compared to past centuries.

https://www.parents.com/getting-pregnant/trying-to-conceive/...

It's not just about the ability to conceive though. Testosterone is a hormone that has very wide ranging effects.[0] The regulation of sex-drive alone could have an impact on the fertility rate.

[0] https://www.nih.gov/news-events/nih-research-matters/underst...

I think this overthinks the situation. Kids are an expensive luxury in first world countries, which many can’t afford and a proportion who can don’t want them.

At the same time, in environments with easy access to contraceptives and where women are educated and empowered, the fertility rate falls without fail (per Our World In Data).

https://ourworldindata.org/fertility-rate

I think even with reduced sex drive, the chances are that you would still be able to have sex successfully at least 3 times in your fertile life.

The "issue" – and lets face it, a gradual, managed decline in population is just what the Earth ordered – is that we have collectively decided we would like fewer kids and are deploying birth control.

The data in this Parents article is really out of date

I can’t find the white papers I want to cite but here’s a better article, even though it’s also older

https://www.washingtonpost.com/health/2018/10/19/us-fertilit...

Even accounting for social (contraception and abortion) and economic changes, fertility has gone down in developed countries

>We don’t know why. If I were to guesss, due to the use of plastics with our food.

What evidence do you have to dismiss the (IMO much, much more plausible) idea that it's just men becoming more sedentary, moving and exercising less?

Also... I agree w/ one of the other commenters that declining testosterone does not appear to be an obstacle to couples intentionally trying to conceive, so I would be very hesitant to (essentially) blame plastic in food for declining population.

Because there are residual differences in testosterone for the intergenerational comparisons after controlling for physical activity.

> after controlling for physical activity

You say that like it's easy to do. It's not. That's not directly measurable, certainly not across generations. It's only barely become measurable in the past five or six years.

How would you go about getting this information in the 1970's? Self-reported data would be the best you can do. Getting actual measurements of that information is something which (I suspect) is not available at a large scale beyond a few years of data. Whether it is (even now) linked to measurements of testosterone at a large scale is doubtful.

I doubt that there is high-quality data on actual physical activity at a large scale at all, let alone linked to measurements of hormone levels from any of the 1990's, 1980's, 1970's, ... etc. It will only get much much harder going back.

So "controlling for" physical activity is a non-trivial task in the very best case.

My understanding is that we’d expect to see it leveling off if that’s the case, but every year it just keeps dropping.

This is a popular theory but, plastics and other hormone disrupters are everywhere, including places with high birth rates and strong machismo cultures. The controlling variable is women’s rights and their ability to control their bodies. The sooner we can internalize that fewer women are choosing to have children, and when they do they choose to have fewer, the sooner we can start to make social and policy changes to address it.

So you discount the idea that when people have the choice not to have large numbers of children (good healthcare to provide for old age, easily accessible contraception) they prefer to have fewer children?

Also, the central premise of the article seems to be in dispute:

Professor David Coleman from the University of Oxford said: 'Much has been written about the 'Death of the West', with its threatened demise reportedly due to the low level of reproduction in Western countries. We show that this so-called decline has been exaggerated and trends in European fertility have been misunderstood.

https://www.sciencedaily.com/releases/2015/04/150427211644.h...

I can’t find the white paper, but the decline in fertility rate takes into account social changes such as contraception. In fact, if I remember it correctly, social changes masked the decline

> On the bright side, the threat of overpopulation is lessened

That's a significant bright side. Personally, as someone who enjoys spending time in nature, I would much rather deal with the problems of underpopulation than overpopulation.

seriously - what is the problem with 'underpopulation'?

just the fact the the financial system is structured around infinite growth?

Yep, that's pretty much it. But don't underestimate the difficulty of solving this problem. The entire structure of human society currently rests on this assumption. Discharging it is not easy.

It's just not the financial system, though, it's our entire societies that are designed with growth in mind. It's obvious we need some kind of alternative way to solve this, but getting from here to there isn't something one just does.

I think issues are a lot less complex than you think.

From anecdata, it simply looks like the burden of government, extended family, and increasing QOL costs, is much greater than ever on childbearing age men & women, for those living in developed countries. For example, men and women only started to take 10-30 year debt to buy a house, or to become a nurse...in the last 50 or so years.

Thus, there are far fewer resources (including testosterone!) for child-rearing.

Take for example what psychologists say about males being less fertile when they make less money than their partners, for example.

Not having an opinion on whether this is good or bad. It just seems to be true.

The lowered fertility rate accounts for economic and social factors. This is biological and it started in the 1950s. It was masked by social changes starting in the 1960s

This is false. Birth rates are down because people are choosing to have fewer children, not because something is preventing them from having children they want.

Obesity and sedentary lifestyles are probably bigger factors in declining testosterone levels.

>testosterone keeps falling consecutively every year in developed countries. We don’t know why.

the more developed the society is the less valuable are the testosterone benefits like the ability for heavy physical work in harsh conditions, etc. and the less tolerance the society has for the testosterone driven behavior - thus natural selection drives testosterone down. For example when you have a car accident, display of rage would put you in a losing position in US where you just need to exchange insurance info, and your higher muscle mass and hand-to-hand combat skills decide nothing, whereis for example in Russia the rage is a synergetic addition to the metal tire tool in you hand displayed as a credible threat. Another correlation which would suggest why testosterone would be selected out from government and management positions in developed societies:

https://onlinelibrary.wiley.com/doi/abs/10.1111/kykl.12169

" To measure testosterone exposure, we apply the facial width‐to‐height metric (fWHR) – a standard proxy widely used in the psychological literature – and look at a sample of Russian regional governors. We find a positive relationship between the fWHR of the governor and the level of repression in his region. "

Please stop repeating the "testosterone==aggressiveness" falsehood. There isn't a 1:1 correlation. Humans are way more complex than that.

> thus natural selection drives testosterone down

Also you are implying that natural selection is currently existing in human society. It does not.

...and that such selection works so fast that it changes human genome within a generation of two. This is simply impossible.

>Please stop repeating the "testosterone==aggressiveness" falsehood. There isn't a 1:1 correlation.

i didn't say "==". I stated "->", i.e. positive causality from testosterone to aggressiveness (The opposite is obviously not true as evidenced by aggressiveness without testosterone, say in women).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693622/#:~:tex....

"Atavistic residues of aggressive behavior prevailing in animal life, determined by testosterone, remain attenuated in man and suppressed through familial and social inhibitions. However, it still manifests itself in various intensities and forms from; thoughts, anger, verbal aggressiveness, competition, dominance behavior, to physical violence. Testosterone plays a significant role in the arousal of these behavioral manifestations in the brain centers involved in aggression and on the development of the muscular system that enables their realization. There is evidence that testosterone levels are higher in individuals with aggressive behavior, such as prisoners who have committed violent crimes."

>Also you are implying that natural selection is currently existing in human society. It does not.

natural selection never stops. Some people naively think that the "fittest" necessarily means strongest/healthiest/etc. which is just not the case.

So, then it comes to the drivers, one can say that societal natural selection is less "natural" (in that very naive understanding of it) and more like selective dog breeding and similarly it works very fast. Add to that the positive feedback between testosterone production and testosterone style behavior - ie. the more testosteronish style behavior of an individual causes more testosterone production in his body and vise versa (that famous barn swallow experiment where they painted the male bird chests dark to fake high testosterone characteristic or the article referred above:

"Several field studies have also shown that testosterone levels increase during the aggressive phases of sports games. In more sensitive laboratory paradigms, it has been observed that participant’s testosterone rises in the winners of; competitions, dominance trials or in confrontations with factitious opponents.").

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