if the total fertility rate drops and stays below global replacement rate, will humans disappear?

Submitted ⁨⁨3⁩ ⁨months⁩ ago⁩ by ⁨notsofunnycomment@mander.xyz⁩ to ⁨[deleted]⁩

After watching this video I am left with this question.

The video ultimately claims that humans will not disappear, but doesn’t do a great job explaining why.

Correct me if I’m wrong, but for the (or a) population to be and remain stable, the total fertility rate needs to be equal to the global replacement rate (currently 2.3).

And since the total average fertility rate appears to be currently at this 2.3, any drop in the fertility rate in place A would have to be compensated with a rise in the fertility rate in place B (assuming that, at some point, we would like to stop population decline)?

I guess one way for a population to remain stable, while women are having fewer than 2.3 children, would be to have fewer men? If a population has 100 women and 10 men, each woman would only have to have on average (a bit more than) 1.1 child? (Which would of course also require a collective form of prenatal sex selection.

I realize that would be bonkers and unethical. Just wondering out loud.

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Comments

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BlameThePeacock@lemmy.ca ⁨3⁩ ⁨months⁩ ago
If it stays there forever, yes.

It won’t though, as there become fewer humans it’s likely it will become easier to have more children again (fewer people for the same amount of finite resources) and the rate will increase.

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- NeoNachtwaechter@lemmy.world ⁨3⁩ ⁨months⁩ ago
  
  (fewer people for the same amount of finite resources) and the rate will increase.
  
  Funny way to think…
  
  Actually it is poor countries (less ressources) that have the higher birth rates.
  
  I’d say, having children is hard work, but people in rich countries are lazy :-)
  
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  - FeelzGoodMan420@eviltoast.org ⁨3⁩ ⁨months⁩ ago
    That is a really naive and kinda braindead take on why rich nations have less kids. The more likely reasons, and more commonly accepted reasons are:
    
    better career opportunities for women
    
    costs of children
    
    challenges with child care
    
    education
    
    access to contraceptives
    
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  - redisdead@lemmy.world ⁨3⁩ ⁨months⁩ ago
    People from poor countries that move into wealthy countries adopt the birth rate almost immediately.
    
    It isn’t about laziness, it’s about education and wealth.
    
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  - BlameThePeacock@lemmy.ca ⁨3⁩ ⁨months⁩ ago
    You’re thinking about the resources wrong. I mostly mean land availability.
    
    Even in first world countries the birth rates are higher outside cities than inside. In undeveloped counties the birthdates are lower in crowded cities.
    
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saltesc@lemmy.world ⁨3⁩ ⁨months⁩ ago
Mathematically? Obviously, yes.

Socially? Would never happen. Imagine our population is just stock. It goes up and down depending on how good things look. At some point, it cannot continue as it’s not financially feasible. But when it drops back down into realistic numbers, balance goes up again.

You can see this behaviour in the generations (Z, Y, X, Boomer, Pre-war, etc.) These generation changes are marked by a tipping point of birthrate increasing or decreasing in a nation—typically globally, which is why we all tend to agree on the start/end of generational eras within 3–5 years.

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- FaceDeer@fedia.io ⁨3⁩ ⁨months⁩ ago
  Not to mention that technology is continuing to advance in new and unexpected ways.
  
  We're getting close to artificial womb technology, for example. There are already artificial wombs that are being experimented with as a way to save extremely premature babies that wouldn't survive in a conventional incubator, for example.
  
  Commodity humanoid robots are also in development, and AI has taken surprisingly rapid leaps in development over the past two years.
  
  I could see a possibility where in a couple of decades a human baby could be born from an artificial womb and raised to adulthood entirely by machines, if we really really needed to for some reason. Embryo space colonization is the usual example given, but it could also potentially work as a way to counter population decline due to people simply not wanting to do their own birthing and child-rearing.
  
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Sgt_choke_n_stroke@lemmy.world ⁨3⁩ ⁨months⁩ ago
No, the only people complaining about replacement rates are governments that are in bed with corperations that need endless growth to feed thier capitalists machines.

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bear@lemmynsfw.com ⁨3⁩ ⁨months⁩ ago
No, because it won’t stay down that low. No need for funny maths; some people enjoy making babies.

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jaycifer@lemmy.world ⁨3⁩ ⁨months⁩ ago
Let me spoil part of the Foundation series for you. In one book, the cast visits a planet where they encounter one person with psychic powers surrounded by robot servants. He reveals that the planet is evenly divided by I think 128 people like himself who want for nothing and live comfortably. They only reproduce asexually, and only in preparation for their own death or when another dies.

What this illustrates that’s relevant for you is that yes, not hitting the replacement rate could lead to significant population decline, but only until people are comfortable enough and want to have kids or feel it is the best way to maintain their way of life (think farmers having kids to help on the farm).

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Mediocre_Bard@lemmy.world ⁨3⁩ ⁨months⁩ ago
If a generation is 25 years, there 7.9 billion people on Earth, and the replacement rate is 1.0, then humans will disappear in about 800 years.

If we enforced a 1.0 replacement rate for two generations, the global population would decrease by 75%, leaving 1.9 billion people in play. This is the global population in 1919. If we go three generations, we could get down to 985ish million prople.

That would be amazing for our climate goals and would be considered ethical and humane by most.

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- lovely_reader@lemmy.world ⁨3⁩ ⁨months⁩ ago
  Would the shrinkage in the labor force make it impossible to provide end of life care and financial support as the larger generations age?
  
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  - Mediocre_Bard@lemmy.world ⁨3⁩ ⁨months⁩ ago
    Yep. We would have to back to villages at some point.
    
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  - Spacehooks@reddthat.com ⁨3⁩ ⁨months⁩ ago
    Robots
    
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- yes_this_time@lemmy.world ⁨3⁩ ⁨months⁩ ago
  Restricting reproductive rights is not ethical.
  
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  - LordGimp@lemm.ee ⁨3⁩ ⁨months⁩ ago
    Unlimited reproductive rights is also unethical. Unlimited growth is not sustainable in a finite environment. As masters of our environment, it is our moral responsibility to ensure our existence does not destabilize everything else. We’ve done so poorly as a species that the world is about to undergo a cataclysmic shift.
    
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  - daq@lemmy.sdf.org ⁨3⁩ ⁨months⁩ ago
    What if selection is truly random?
    
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PenisDuckCuck9001@lemmynsfw.com ⁨3⁩ ⁨months⁩ ago
If the government wants my cum they’ll have to cum and take it. I’m never having kids unless a lot of shit improves.

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- BackOnMyBS@lemmy.autism.place ⁨3⁩ ⁨months⁩ ago
  omg, a gem! this is the quality shit i suffer thru hours of mindlessly browsing on the internet for. thank you, PenisDuckCuck 😘
  
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aubeynarf@lemmynsfw.com ⁨3⁩ ⁨months⁩ ago
We are currently overtaxing natural resources, human population cannot grow unbounded without many unpleasant consequences. To me, it’s not a problem if we reach a steady state or even start a slow downward trend.

But, we must turn away from “line goes up” methods for measuring success, which are pretty deeply ingrained in most of our economies.

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Fermion@feddit.nl ⁨3⁩ ⁨months⁩ ago
The human population isn’t homogenous. Some regions and cultures have a lot more children per woman than others. So some demographics will experience population decline and others will continue growing. Overall, the world population may go into decline, but we are a very long way away from anything resembling extinction.

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dhork@lemmy.world ⁨3⁩ ⁨months⁩ ago
So, as long as some humans are successfully making new humans, whether or not the rate is exactly 2.3 is irrelevant. World population has been skyrocketing for the past 100 years. It wouldn’t be the worst thing in the world for that to backslide a bit. It can probably go down 5x and we’d still feel like the place is crowded.

The only thing to worry about is some widespread event that affects fertility workdwide. Like what if these micro plastics are really getting into our testicles and reducing sperm counts? They are getting everywhere. If men everywhere started shooting mostly blanks then we would all be in a panic.

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- NoIWontPickAName@kbin.earth ⁨3⁩ ⁨months⁩ ago
  They’re not blanks.
  
  It’s tactical chaff to avoid detection until one of the real warheads strikes home.
  
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teft@lemmy.world ⁨3⁩ ⁨months⁩ ago
As the population declines we would probably reach a point where we have to go back to agrarian societies and those pretty much need a bunch of child workers working the farm with the parents.

My thought would be no, we won’t disappear unless it’s a cataclysmic event that just wipes us all out at once. Also if we can get off this rock and establish a base somewhere else like the moon or mars that increases our chances of not being extinguished even higher.

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- NeoNachtwaechter@lemmy.world ⁨3⁩ ⁨months⁩ ago
  
  we have to go back to agrarian societies
  
  But why would we have to?
  
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  - teft@lemmy.world ⁨3⁩ ⁨months⁩ ago
    Because if the fertility rate stays the same there will become a point where societies will become too small and disconnected to maintain technology. At that point people will probably have to fall back on farming in order to survive. When that happens you’ll have to maintain large families in order to keep everyone fed.
    
    It’s not like our birth rates are falling due to some outside cause. It’s because modern societies don’t require many children in each family. Give that cause back and the birth rates will explode.
    
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John_McMurray@lemmy.world ⁨3⁩ ⁨months⁩ ago
Ok so there is stupid questions. No. Next.

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iiGxC@slrpnk.net ⁨3⁩ ⁨months⁩ ago
The replacement rate isn’t static. It depends on both how many people exist and how many people are having babies and how many babies they’re having. If the total number of babies stays constant, then whether it’s below or above the replacement rate depends on the size of the population. So for a hyper simplified example, if 100 babies are born per yer, that’s below replacement for a population of 110, but above replacement for a population of 90, but overall the population size will trend towards 100. Obviously real life is way more complicated, but even if the birth rate is low now, it’s far more likely we’re just moving towards a different population size, not a population of zero

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- notsofunnycomment@mander.xyz ⁨3⁩ ⁨months⁩ ago
  Expressed as “the average number of babies that an individual woman needs to have for a certain population to stay the same size”, the replacement rate should not depend on population size, right?
  
  If you express it as an absolute number (e.g. number of babies per year) than obviously it will depend on population size.
  
  From what I understand, the replacement rate (expressed as the average number of babies that an individual woman needs to have for a certain population to stay the same size), depends mostly on what percentage of people die before they (can) have babies.
  
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notsofunnycomment@mander.xyz ⁨3⁩ ⁨months⁩ ago
Thanks all for your replies. Interesting.

I’m a bit surprised that nobody comments on the matriarchal speculation at the end. You’re all fine with that?

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- sanguinepar@lemmy.world ⁨3⁩ ⁨months⁩ ago
  I think if you hadn’t described it as bonkers and unethical you might have had some views on that! ;-)
  
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- Deestan@lemmy.world ⁨3⁩ ⁨months⁩ ago
  
  I’m a bit surprised that nobody comments on the matriarchal speculation at the end. You’re all fine with that?
  
  Mathematically, I am not fine with that. The only way to have fewer men would be late-stage abortion or to murder newborns. Each woman would need to have 1.1 (surviving) children but still 2.3 born or nearly born children. While this may raise some ethical questions by itself, the greater crime is that it artificially inflates a metric without achieving the stated goal. It is lie by misapplication of statistics.
  
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  - notsofunnycomment@mander.xyz ⁨3⁩ ⁨months⁩ ago
    That’s why I said:
    
    Which would of course also require a collective form of prenatal sex selection
    
    If the goal would be to have a stable population size but with fewer births per woman, I think a collective form of prenatal sex selection (of the kind I describe above) would work.
    
    What this sex selection would look like would be another issue. Whether externally fertilized embryos are selected before they are placed in a womb, or whether it would involve forms of abortion (or even infanticide): it’s up to your imagination.
    
    But there are no lies, nor any misapplied statistics?
    
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