> Humans aren't about to go extinct but it's high time their population numbers stabilised, perhaps even reduced a bit.
There's little evidence to support the theory that at some point in the future, little girls will all suddenly decide to buck the trend set by their mothers, grandmothers, great-grandmothers, and all the adult women they see around them in the world, and have 2.1 children themselves.
But, if they do not all do this, if only some of them decide to buck the trend, they those girls would need to have 3 or 5 or 8 to make up for those who do not.
If neither of these things happen, population cannot stabilize. Mathematically, there has to be an average of 2.1.
Fertility rate declines are future extinction. They've run the experiments, and the results are always the same... despite having all the food and water and entertainment they might want, the mice either do not fuck or they just murder whatever offspring they do (rarely) have. And it happens more quickly than one might expect, because the rate of decline increases with each generation.
> the human branch be pruned the remaining mass of the tree of life on earth might very well thrive and surge in breadth and depth after a rather large number of other prunings at the hands of humankind.
And why should any human ever give a shit about whether these non-human organisms thrive, especially when hypothesizing a future where humans no longer exist? Sounds like some death cult nonsense. Will you be one of those lamenting how you think the most beautiful planets of all are those with no life whatsoever to "mar their beauty"?
> There's little evidence to support the theory that at some point in the future, little girls will all suddenly decide to buck the trend set by their mothers, grandmothers, great-grandmothers, and all the adult women they see around them in the world, and have 2.1 children themselves.
There is some speculation - and some data which may or may not support it - that fertility may follow a "J" curve where it declines sharply with increased development and then slowly rises again above a certain level.
There is also some data to suggest that within a population, if a subset sees an increase in wealth, it can predict an increase in fertility within that subset.
Combined, a suggestion that does not seem unreasonable is that we develop certain expectations based on societal expectations, and as they increase it becomes harder and harder to justify additional children, but when people find themselves able to meet those expectations, the number of children goes up.
If that holds, then that would suggest the rate can be brought back up with sufficient societal assistance, which may or may not come as fertility rates becomes enough of a political issue. Whether that will actually work remains to be seen - we've already of course seen some pretty significant attempts, such as the escalating Hungarian family support scheme (total support for 3+ children amounts to over 300k Euro, of which about 1/3 is a non-refundable grant and the rest subsidized house loans), so we should start to get an idea of what a realistic cost to drive the rates back up will be, if it is viable, over the coming couple of decades as more countries experiment.
> There's little evidence to support the theory that at some point in the future, little girls will all suddenly decide to buck the trend set by their mothers, grandmothers, great-grandmothers, and all the adult women they see around them in the world, ..
What nonsense.
The very evidence you seek is right here, right now, all about us - a world in which men and women have a reproduction rate lower than than their grandparents and great grandparents. They have clearly bucked the trend of those in times past. Q.E.D.
BTW, this focus you have on breeding "little girls" is distasteful to say the least.
> those girls would need to have 3 or 5 or 8 to make up for those who do not.
Only if the world is to return to the present 8+ billion after a fall below.
Should numbers slowly decline down to, say, 1950s world population levels and mean reproduction rates go to 2.1 then things will stabilise.
> If neither of these things happen, population cannot stabilize.
Faulty logic, as already explained.
> And why should any human ever give a shit about whether these non-human organisms thrive
My response was to a human who was waxing lyrical about 3.7 billion years of life, an infintesimal number and tonnage of which was actual humn life ... you should ask them why they care about other lifeforms.
>The very evidence you seek is right here, right now, all about us - a world in which men and women have a reproduction rate lower than than their grandparents and great grandparents. They have clearly bucked the trend of those in times past. Q.E.D.
From the graph I saw the total fertility rate in the US has been falling since 1800 (start of the graph). It briefly improved after WW2 for a bit and then started falling again. There was another brief increase at the end of the 90s and it's been dropping to historical lows ever since. It's not just two generations - it's 200 years and possibly longer.
It would appear that we both agree that population changes rates can alter over time and that it's happened in the past and can happen in the future then.
Unlike the other commenter who has claimed that once a rate has been set it cannot change.
> he very evidence you seek is right here, right now, all about us - a world in which men and women have a reproduction rate lower than than their grandparents and great grandparents. They have clearly bucked the trend of those in times past. Q.E.D.
Are you daft? If fertility rates were high in the past, if they were 6 or 8 or 9.7... they could fall for a long time with no decline in population.
But once they dip below the magic number of 2.1, then population declines. That's how this works. That's the number of children a woman (every woman, on average) must have for population to remain the same from one generation to the next.
I don't know any other way to explain it. You probably think you're intelligent. You followed the teacher's instructions and got an A on math, but you never really understood it. If you follow the recipe, it just poops out correct answers... but here we have a novel problem, and you just can't get it.
> Only if the world is to return to the present 8+ billion after a fall below.
No. For the population to plateau out and stay the same, they'd need that many. It's how fucking averages work.
Either all of them have 2.1, or if only half have children, then they need to have 4.2.
And this isn't for the population to grow again. It's for it to plateau out and remain the same as it is.
> Should numbers slowly decline down to, say, 1950s world population levels and mean reproduction rates go to 2.1 then things will stabilise.
That's the fucking point. If population declines, it's already below 2.1
And if it's below 2.1, that becomes the norm and it never goes back above 2.1. No little girl grows up in a world of childless adults, of the rare "only child", and "only child" herself and says "I think I will do what ever woman I ever knew wouldn't do, and have 2.1".
It's a simple fucking idea.
> You might perhaps ask yourself why you do not.
Because I don't belong to a death cult that hates humanity. I mean, I shouldn't have to say it out loud, but there it is.
No. I still recall studying population dynamics, predator | prey cycles, etc as part of non linear dynamics in mathematics classes back in the 1980s.
> But once they dip below the magic number of 2.1, then population declines.
That magic number can change.
It's relatively easy for anyone to find observational examples of populations with adaptive reproductive rates.
> I don't know any other way to explain it.
Perhaps you might try studying mathematics.
> Because I don't belong to a death cult that hates humanity.
The question was about life on earth, not specifically humanity, the notion that you belong to a humanity hating death cult is frankly one that would not occur to most people .. but here you are going straight there.
Which goes back to my original comment, where I talk about for it to change, the little girls of the youngest generation have to grow up and choose to have more children than their parents. They all have to choose this simultaneously, or the few that do choose it have to choose to have far, far more than 2.1 themselves.
Both of these scenarios are so outlandish, that you keep dancing around it, pretending that I'm describing it incorrectly. You don't want to think about it, or don't want others to think about it, or you just aren't capable... I can't tell which.
It'd be laughable, if I didn't think you were an enemy of humanity.
There's little evidence to support the theory that at some point in the future, little girls will all suddenly decide to buck the trend set by their mothers, grandmothers, great-grandmothers, and all the adult women they see around them in the world, and have 2.1 children themselves.
But, if they do not all do this, if only some of them decide to buck the trend, they those girls would need to have 3 or 5 or 8 to make up for those who do not.
If neither of these things happen, population cannot stabilize. Mathematically, there has to be an average of 2.1.
Fertility rate declines are future extinction. They've run the experiments, and the results are always the same... despite having all the food and water and entertainment they might want, the mice either do not fuck or they just murder whatever offspring they do (rarely) have. And it happens more quickly than one might expect, because the rate of decline increases with each generation.
> the human branch be pruned the remaining mass of the tree of life on earth might very well thrive and surge in breadth and depth after a rather large number of other prunings at the hands of humankind.
And why should any human ever give a shit about whether these non-human organisms thrive, especially when hypothesizing a future where humans no longer exist? Sounds like some death cult nonsense. Will you be one of those lamenting how you think the most beautiful planets of all are those with no life whatsoever to "mar their beauty"?