[quote=__HRB__;175217]Humans have no enemies left, so their population simply grows exponentially until there is a limiting factor, but human ingenuity currently keeps removing limiting factors.
[/quote]

Have you any idea how much it costs to rear two children and put them through college?

[quote=garo;175230]Have you any idea how much it costs to rear two children and put them through college?[/quote]

Education is predominantly a [URL="http://en.wikipedia.org/wiki/Signalling_%28economics%29"]signaling device[/URL].

Since intelligence is a positive trait and education has served as a signal for intelligence, social parasites will try to mimic the signal. Which is why the world is polluted with educated morons.

For $200.000 you can start 4 businesses or go to 4 years to college. If the investment into education doesn't pay off through discounted profits on human capital, smart people will be the first ones to realize this and choose the strategy with the higher pay-off.

If you have to go into debt for $200.000 for your kids to get degrees in History-of-Art, you really shouldn't have any money (and neither should the lender) and your kids would probably be better off living in the streets, receiving lessons in survival-of-the-most-sly.

[quote=CRGreathouse;175226]If that was true, you'd have explosive population growth in Europe.[/quote]

Hm...that's a reasonable objection...

But, you are forgetting that there is a trade off between [URL="http://en.wikipedia.org/wiki/R/K_selection"]r and K strategies[/URL], so as soon as it becomes more efficient to increase r, we'll see more population growth again (and note that for K>>0, r dominates). Trade-offs between r and K would also explain periods of faster than exponential growth.

Since the 1970s humans have been trying to give their offspring an advantage by giving them higher education (higher K), but of course this cannot work, for the above reasons.

This would explain the recent anomalies, but older population figures are only estimated and smoothed, which is why we only see non-smooth data for the most recent years.

[QUOTE=__HRB__ (emphasis mine);175217][COLOR="Orange"]this requires us to wipe[/COLOR] out nincompoops like [COLOR="#ffa500"]Uncwilly[/COLOR] who's solution to allocation problems involves a totalitarian world government, run by benevolent, omnipotent and omniscient supermen.[/QUOTE]You assume that the solution involves totalitatianism. Do you not think that an educated democracy can achieve this? Oh, BTW, don't forget that a nice thermonuke war can achieve a vast population reduction involuntarily, whoever may start or be involved.

The current level of demand of the human population is creating a number of problems that are effecting the world. Not all of these are CO2, some are: water (the elephant in the room that more and more is getting spoken of), soil damage, ecological "infrastructure" damage, damage to spieces populations that is beyond us to repair (and totally imoractical for any forseeable period), depleation of fixed quantity resources, to name some of the bigger ones.

You obviously do not understand my personal view point completely enough.

[QUOTE=__HRB__;175236]Hm...that's a reasonable objection...

But, you are forgetting that there is a trade off between [URL="http://en.wikipedia.org/wiki/R/K_selection"]r and K strategies[/URL], so as soon as it becomes more efficient to increase r, we'll see more population growth again (and note that for K>>0, r dominates). Trade-offs between r and K would also explain periods of faster than exponential growth.

Since the 1970s humans have been trying to give their offspring an advantage by giving them higher education (higher K), but of course this cannot work, for the above reasons.[/QUOTE]

Signaling has very little to do with K-selection. There are many ways parents can invest resources in their children which actually increase fitness.

But I believe the dominant theories on the demographic transition focus on the cost/benefit to the parents rather than their best ESS. This seems to have more predictive power. It suggests that when children who help bring in the harvest and are inexpensive to raise, women will tend to produce large numbers of offspring, while when children are expensive to raise and do not immediately bring in revenue fewer offspring will be produced.

But even if you reject the economics/Law of Demand for the biology/r/K selection, I'm puzzled as to why you'd suggest that as population nears (or passes) holding capacity, r selection would dominate. The whole idea of the model is that K-selection would dominate under those circumstances, no?

[quote=Uncwilly;175246]You assume that the solution involves totalitatianism. Do you not think that an educated democracy can achieve this?[/quote]

No. The main problems are:

1. Rational individuals don't vote because of [URL="http://en.wikipedia.org/wiki/Rational_ignorance"]rational ignorance[/URL], so there is a selection bias towards irrational voters.

2. Determinants of rationality follow a log-normal distribution, so the median vote is biased towards inferior strategies, compared to an averaging mechanism that is correlated with rationality. Individuals who are better at determining trade-offs between risks and rewards have higher incomes, so a superior mechanism would be e.g., to allocate votes according to paid income taxes. It is not a coincidence that the most powerful corporations operate on the principle of votes per share and not per shareholder. As a perk, this would also crate an incentive to pay taxes.

[quote=Uncwilly;175246][...] and more is getting spoken of), soil damage, ecological "infrastructure" damage, damage to spieces populations that is beyond us to repair (and totally imoractical for any forseeable period), depleation of fixed quantity resources, to name some of the bigger ones.

You obviously do not understand my personal view point completely enough.[/quote]

The issue is that your view is based on what you think is 'forseeable'. It is not important what a majority believes will happen, but what is more likely to happen.

Stock markets peak when everybody is fully invested in the belief that things will go up, so consequently things go down because there are no buyers.

[quote=CRGreathouse;175247]But even if you reject the economics/Law of Demand for the biology/r/K selection, I'm puzzled as to why you'd suggest that as population nears (or passes) holding capacity, r selection would dominate. The whole idea of the model is that K-selection would dominate under those circumstances, no?[/quote]

Well, the assumption is of course that K(t)~N(t), since larger N means that there are simply more brains thinking about how carrying capacity can be increased, which would mean that asymptotically dN/dt~r*N.

The number of free parametes in a fully connected graph is proportional to N^2, so it is not entirely unreasonable to assume that the decentrailzed problem-solving machine 'mankind' could be able to solve much more complex problems in the future, than people can 'forsee' today using linear extrapolation.

If that's the case, though, there's no problem with being r-selected.

But the UN Population Division (and the US Census Bureau) seems to expect otherwise: both project population approaching a horizontal asymptote near N = 10 billion. (I'm not qualified to comment further on the demographics.)

[quote=CRGreathouse;175259]If that's the case, though, there's no problem with being r-selected.

But the UN Population Division (and the US Census Bureau) seems to expect otherwise: both project population approaching a horizontal asymptote near N = 10 billion. (I'm not qualified to comment further on the demographics.)[/quote]

I don't think those numbers are unreasonable if we limit ourselves to counting heads on Earth, but as soon as we can e.g. grow humans outside of the human body, we could create individuals with bigger heads containing bigger brains consuming more energy per capita...

Colonizing the solar system would severely limit the risk of wiping out mankind with nukes: too many targets.

[QUOTE=__HRB__;175261]I don't think those numbers are unreasonable if we limit ourselves to counting heads on Earth, but as soon as we can e.g. grow humans outside of the human body, we could create individuals with bigger heads containing bigger brains consuming more energy per capita...[/QUOTE]

Do you have an idea of what % of energy expenditures are food? I'm curious -- all the better if you have a reputable source and a link. I wouldn't think it would be that great.

I think juxtaposing that (seemingly far-)future concern with modern social dynamics is misplaced. But I could be convinced otherwise.

[quote=CRGreathouse;175262]Do you have an idea of what % of energy expenditures are food? I'm curious -- all the better if you have a reputable source and a link. I wouldn't think it would be that great.[/quote]

A 2000 Kcal diet would generate about 100 watts, so according to [URL="http://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita"]this list[/URL], that would be around 1% for Americans and 30% for Senegalese.

P.S. my first guess would be that energy consumption is proportional to skin surface, i.e. mass^(2/3). I think the brain is organized in layers, which would also be mass^(2/3).

So, ballpark -- worldwide energy expenditure would be reduced by about 1% if every human being cut the energy equivalent of their diet in half, maybe 2% if they cut it to 10%. Or, alternately, if all humans grew brains five times their current size, this would increase energy expenditures by about 2% ([i]ceteris paribus[/i]).*

To make a real dent in energy use we'll have to change heating, cooling, transportation, chemical production, metalworking, and other energy-hungry sectors.

* Implicit ballpark assumption: the brain consumes a quarter of the body's energy. Modify to suit.