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"Every age seems to feel it is on the brink of an apocalypse – check out Richard Erdoes A.D. 1000 for a description of how Europe approached the millennium with its nightmare visions."

Also worth reading along the same vein is Tom Holland's Millennium (actually, all his history books are quite good).

Ditto Bob's recommendations. A quick review of journalism archives from 1999, and the dawn of 1984, have the same po-faced pseudo-certainty as today's doomsayers.

There are many different projections of future world population out there, including some that show a decline. However as with water, money, and skill, the issue is not the total quantity but allocation. Rapid growth of the population in Yemen, where the median age is about 17 and water resources are extremely stressed, has a lot of downside. A surge in fertility/immigration and population in Canada or Australia would be a good thing. This is why the fruit-fly analogy doesn't carry over to humans, as you say. Humans have the ability to allocate, including over the long term (not always very well, mind you, and not consistently). A population graph like the one above, but for spiders or seagulls rather than humans, would likely be more ecologically devastating than a human one.

Apocalyptic scenarios are just our way of thinking things through. It is best to bear in mind that our greatest obstacles are never those that dominate our thought at any time but will always lie before us, waiting to be discovered.

1. I will never understand why intelligent people waste their time reading stupidity like Dan Brown. Isn't there some concept out there called opportunity cost? Why not read a classic instead, say Dostoyevsky or Dumas (if you want a quick dose of action and thrills). Ok, maybe that's too high brow. Sometimes one's brain craves junk food. I understand. Watch an old episode of Survivor instead (for the game theoretic aspects), or just TV in general. Yes, TV stuff, even the reality shows, are more intelligent than "books" written by folks like Dan Brown (not that's saying much). Is this some kind of cultural thing I'm not privy to? Like everyone knows it's stupid but everyone reads it simply because everyone else reads it, so it survives because it's a focal equilibrium for possible conversation topics?

2. Please don't do injustice to Malthus by lumping him in with the so-called neo-Malthusians. Malthus never predicted “end of the world population scenarios”. Just that population would adjust to keep standard of living constant. It's pessimistic, but not apocalyptic. There is a difference. Which is not appreciated by most of these "neo-Malthusians".

3. Speaking of pessimism, and nit picking to some extent, it's actually not true that "The essence of the Malthusian analysis (is) that population increases geometrically while resources increases arithmetically means that population will outstrip resources ". You can have BOTH population and resources (technology) grow geometrically and you can STILL get a Malthusian trap. The necessary condition is that (in addition to diminishing returns to labor) technological growth is slower than maximum possible population growth. Put growth of population on y-axis and income per capita on x-axis. Draw a constant growth of labor productivity curve, a horizontal line. Draw an increasing, concave, function representing population growth. If they cross you got a Malthusian trap even though technology is growing "geometrically" (exponentially). If A is technology, geometric technological growth is (dA/dt)/A=g. Arithmetic technological growth is (dA/dt)/A=g/A. Not necessary and an unnecessary distraction in fact (because a sentence like "population increases geometrically while resources increases arithmetically" has more rhetorical umpfff)

4. To the extent that there is something to the whole neo-Malthusian idea, as wrapped up in confusion and rhetoric as it is, it has to do with the substitutability of technology for "resources" (whichever are the relevant ones). If technology and "resources" are pretty good substitutes we're ok. If the production function is Cobb-Douglas it's a race between their growth rates. If they're sufficiently complementary then we're screwed. I think this was all in Nordhaus back in the 70's but it's been awhile since I've peeked.

Bob & Shangwen:
Tanks for the reading suggestions and examples.
Interesting - apocalyptic scenarios as a sort of collective species "planning and simulation" function to deal with potential alternative future events?
Not Sneaky:
1. As I said, it was summer entertainment. I also watched Lillehammer, Revolution and Edward VII on Netflix. By the way, Revolution an apocalyptic scenario of what happens if all the lights go off...
2. Good point.
3. As I said, under certain assumptions and "all other things given", that is the result. If you vary assumptions, you can get other scenarios.
4. Good point. I think technology is also a way to expand the resource frontier so to speak and make resources thst were previously difficult to extract more accessible. Think of fracking for example.

No comment on Dan Brown, and I'm not worried about the zombie apocalypse. But it's worth noting that "Malthusian" crashes have been part of the human story for a long time. Elizabethan England, for instance, was less populated than the England three centuries earlier. It's more complex than a simple food and population ration - vulnerability to disease, the ramifying effects of shortages amplified or damped by social structures, and particular critical elements all play a part. There is an interesting literature on this (you could start with Peter Turchin). And while we have, so far, overcome local and short-run problems, those "local" and "short-run" problems usually involved some millions of deaths.

The essence of the Malthusian analysis – that population increases geometrically while resources increases arithmetically means that population will outstrip resources – is correct, all other things given You have to be careful how you phrase that principle. The original version from Malthus has an obvious problem -- all plant and animal food sources are themselves populations.

Darwin took from Malthus his constraint for natural selection to operate, but realised that it was resources external to the biosphere which were the real limit, since it is possible for prey and predator populations to be in balance for long periods of time. Population crashes are not an endemic feature of the natural world, after all. Until an asteroid hits or the Deccan mega-volcano blows or whatever and suddenly everyone's budget constraint gets really vicious.

The focus on human population is anyway inappropriate when what we actually have is a population of men and machines. The thing we ought genuinely to be afraid of is the propensity of all complex systems to maximise the throughput of free energy - e.g. to dissipate free energy from such flows and reservoirs that are available as quickly as possible.

This imperative appears to apply to all complex systems from the weather through to pre human ecologies through to human civilisation. As Brain Cox said in one of his recent documentaries the only real purpose of men and other life forms is to burn energy. And in fact that's the only obvious purpose of machines as well.

So the 'rebound effect' is more frightening than mere population numbers. That is, that an increase in energy efficiency of some human technological process always results in an *increase* in the rate of energy consumption of the whole. Mathematically, like decreasing electrical resistance (decreasing the quantity of electrical energy dissipated as heat) increases power consumption, all else equal.

These kinds of things are intensive changes - e.g. changes which restructure the form and efficiency of the internal processes of human economy and the biome it is embedded in. A mere increase in population is an extensive change which simply scales up what was already there without change.

Likewise one may see muted or slowing population growth and think that there is no problem, while at the same time the amount of energy consumed outside the human body (exosomatic) is running away thanks to various advances, internal restructuring of the whole process or whatever.

So considering population alone without also considering the growth of the machine population alongside is pretty pointless, IMO.

Livio, on #3, I was just pointing out that Malthus' original formulation in terms of geometric vs arithmetic growth is a sufficient but not necessary condition for Malthusian traps. Vary assumptions, get the same scenario (with some subtleties).

If I had a blog I'd write up a "Common misconceptions about Malthus and Malthusianism". Even Malthus misunderstood some Malthusianism (sorry bud, no endogenous oscillations unless you put extra stuff in there.)

"The essence of the Malthusian analysis – that population increases geometrically while resources increases arithmetically means that population will outstrip resources – is correct, all other things given"

We can't beat the problem on the resources side: there's a finite energy supply, among other things, and that's only the simplest of the many reasons why trying to increase the resource side of the inequality is a dead end in the long run.

However, we *can* beat the problem on the population side. Humans *have* invented artificial birth control.

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