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What percentage of people are alive today?

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Re: What percentage of people are alive today?

#21

Post by mlinsey »

tel wrote: post #9

Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

Of course Earth must have some finite carrying capacity, but that's only terrifying if you assume that "The Crunch" is the only way to bring population growth to a halt.

Population growth is already zero or negative in most developed countries if you remove the effects of immigration. If this becomes a consistent rule for all countries once they become fully developed, the real question is not whether we can sustain infinite population growth, but whether we have the resources to support a developed lifestyle for the entire world. Given current technologies and energy sources, the answer is almost certainly "no", but this is a much more tractable problem.

Re: What percentage of people are alive today?

#22

Post by eoghan »

tel wrote: post #9

Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

Nature will find far less technical solutions to this problem. War, poverty, disease will provide a ceiling to this growth.

Re: What percentage of people are alive today?

#23

Post by amalcon »

iskander wrote: post #20
jonathanbgood wrote: post #10

Earlier quoted context omitted.

We use the world population and average life expectancy to calculate births in a year. To connect these point estimates at the varying times in history we use a bounded exponential growth model for births.

I'm still not completely getting it. Let's say in some year there are a billion people alive and the average life expectancy is 50 years. How are these two pieces of information sufficient to determine how many children were born in that year?

You also need the previous year's population. With population and life expectancy, you can approximate the per capita death rate, and then it's a straightforward linear equation.

Re: What percentage of people are alive today?

#24

Post by reasonattlm »

tel wrote: post #9

Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

Malthus was wrong in principle. He didn't understand human action or economics, and that misunderstanding remains very common. See:

http://www.fightaging.org/archives/2006/09/overpopulation.ph...

"Common Malthusianism - the idea that a given resource (such as living space or food) will run out in the future based upon extrapolation of present trends - stems from fundamental misunderstandings about economics, human action and change. We create change in response to our environment; our self-interest leads us to constantly strive at the creation of new resources where old resources are becoming scarce and expensive. This is the path to profit for the individual - and progress for all. One needs a certain amount of willful blindness to avoid seeing the process in action now and in recent history."

Re: What percentage of people are alive today?

#25

Post by tel »

mlinsey wrote: post #21
tel wrote: post #9

Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

Of course Earth must have some finite carrying capacity, but that's only terrifying if you assume that "The Crunch" is the only way to bring population growth to a halt. Population growth is already zero or negative in most developed countries if you remove the effects of immigration. If this becomes a consistent rule for all countries once they become fully developed, the real question is not whether we can sustain…

I agree that such a state doesn't (a) seem impossible or (b) seem untenable if we have sufficient technological advances (solving fusion ignition, perhaps).

What kind of trajectory takes us from here to there (or to a place dense with similar stable solutions) without going through war and famine? Or, how does a developed nation survive in relative bounty surrounded by nations undergoing severe war and famine?

Re: What percentage of people are alive today?

#27

Post by michaelchisari »

btilly wrote: post #15
tel wrote: post #9

Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

You are not alone. If you want to get more scared, read http://www.amazon.com/Collapse-Societies-Choose-Fail-Succeed... . Interestingly from the population statistics alone it is possible to make an argument about the total likely future number of humans that will live. There is debate about whether the reasoning is correct, but it is at least suggestive. See http://en.wikipedia.org/wiki/Doomsday_argument for more.

And maybe once you're done with that, you can read a rebuttal of sorts:

http://www.amazon.com/Coming-Population-Crash-Planets-Surpri...

Re: What percentage of people are alive today?

#28

Post by georgieporgie »

I thought that 'humans', as in, you would see one and say, "yeah, that weird looking guy over there," went back about 2.2 - 2.3 million years.

http://en.wikipedia.org/wiki/Human_evolution

Populations would have been small, but an extra 2.1 million years is a long time.

Re: What percentage of people are alive today?

#29

Post by ANH »

georgieporgie wrote: post #28

I thought that 'humans', as in, you would see one and say, "yeah, that weird looking guy over there," went back about 2.2 - 2.3 million years. http://en.wikipedia.org/wiki/Human_evolution Populations would have been small, but an extra 2.1 million years is a long time.

There have been catastrophic events in that time that some believe acted as population bottlenecks, in particular the Toba eruption 70,000 years ago: http://en.wikipedia.org/wiki/Lake_Toba

Of course, there is much debate about the effect this had.

[edit] In a recent Seminar About Long Term Thinking, a biologist said that there is evidence the human population was reduced to a few thousand by the Toba event. That is the extent of my knowledge on the subject.

Re: What percentage of people are alive today?

#30

Post by jonathanbgood »

robbles wrote: post #14
astrodust wrote: post #11

This back-of-the-envelope calculation appears to be off by a factor of two, which isn't bad. http://en.wikipedia.org/wiki/World_population#Number_of_huma...

this error is because of assumptions about the life expectancy, right?

Yes, their birth rate assumptions would only yield the population milestones they suggest if the life expectancy was significantly below the reported level.
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