I am having difficulty with this thread. As I understand biology:

1. all organisms (not just humans) tend to be able to produce more offspring then the environment can support

2. those individuals that produce the most living (and reproducing) offspring have their genes in higher frequency in the population

3. therefore natural selection works and populations evolve

Both Darwin and Wallace crystallized their ideas on evolve after reading Malthus. It doesn't matter if Malthus was wrong on some minor points - his general idea is one of the foundations of evolution by natural selection. If you throw out Malthus' general idea then you throw out natural selection. You cannot have it both ways.

Also, the idea that famine did not occur throughout human history is naive.

That is a flawed argument, WrongBot. Visible signs of starvation aren't necessary to assume humans were living along Malthusian limits. Rates of violence were extremely high amongst hunter gatherers (homicide was the most common cause of death). According to Stephen Pinker, 20-60% of males were murdered. This shouldn't surprise those of us who understand human nature, people will gladly start killing each other before they let themselves starve to death.

In addition, females menstruating less is a natural response to malthusian conditions. The malthusian limits wouldn't look like hungry bodies, it would look like fewer pregnant women per year, and more murders.

Malthus claimed that human population doubled every 25 years unless limited in some way by the amount of available food.

So if there had been some span of time during which the human population was not limited in any way by a scarcity of available food and did not double at that rate, then that would be evidence that directly contradicts his theory.

Are you reading Malthus, or just listening to the little caricature of Malthus in your head and the popular media? Your own link doesn't even say that!

"In the United States of America, where the means of subsistence have been more ample, the manners of the people more pure, and consequently the checks to early marriages fewer, than in any of the modern states of Europe, the population has been found to double itself in twenty-five years."

Basic grammar tells me that Malthus enumerates 2 checks on the population, only one of which has anything to do with food.

Earlier, Malthus writes:

"I think it will be allowed, that no state has hitherto existed (at least that we have any account of) where the manners were so pure and simple, and the means of subsistence so abundant, that no check whatever has existed to early marriages, among the lower classes, from a fear of not providing well for their families, or among the higher classes, from a fear of lowering their condition in life. Consequently in no state that we have yet known has the power of population been left to exert itself with perfect freedom."

If you wish to not allow this, you need to prove both points: about means of subsistence being so abundant no fear exists, and about manners being pure and simple.

And more generally, you don't grapple with the most fundamental point: population growth can be exponential, and resource growth is not.

So if there had been some span of time during which the human population was not limited in any way by a scarcity of available food and did not double at that rate, then that would be evidence that directly contradicts his theory.

The key point here is "not limited in any way by a scarcity of available food".

The conversation went roughly like this

• WrongBot: Malthus was wrong

• MichaelVassar: what! why?

• WrongBot: Well, here is evidence A (population growth data)

• Emile: What? Evidence A is perfectly compatible with what Malthus said!

• WrongBot: There is also evidence B (no signs of malnutrition in hunter-gatherers, etc.).

What I'm saying is that Evidence A alone is not enough to say Malthus was wrong. And that if you went back in time and showed evidence A only to Malthus, he would shrug. Do you disagree with this?

simply say Malthus is irrelevant when his assumptions (positive relationship between wealth and birth rates, population grows faster than economy) don't hold?

This is the correct view; his argument is practically deductive, and the only way around it is to take one of his escape holes: people collectively choosing a higher standard of living rather than offspring. The real questions we should be discussing are:

1. why does the demographic transition exist?
2. will it last indefinitely?
3. if it willn't, when does it end? And will it reverse itself to high-fertility and either a population increase or a decrease in standard of living?
4. What repercussions does the end of the transition signal?

Question 4 leads us right into Robin Hanson's crack of a future dawn and Dream Time scenario.

WrongBot:

What simple adaptation do you propose to allow individuals to improve their average number of offspring, given that breastfeeding duration and menstruation-onset are traits of present-day foraging societies?

Anything that makes people more phyloprogenitive will do the trick. In the long run, even behavioral mutations are conceivable, but cultural changes can also have a dramatic effect, and they act nearly instantaneously on evolutionary timescales. You yourself provide one possible answer: in the situation you describe, a mere cultural change that would shorten the breastfeeding period would, ceteris paribus, boost the fertility significantly.

Or, for that matter, how do you explain the observed low population growth? Human fossils from that era don't show signs of chronic malnutrition, and present-day foraging societies generally don't have problems acquiring food.

Obviously, the most reasonable explanation for low population growth is that the foragers were in a Malthusian equilibrium. The Malthusian principle says only that some resource constraint will stop further population growth, not what exactly that constraint will be. Other commenters in this thread have already suggested scenarios that wouldn't necessarily leave too many emaciated corpses around.

The facts that early human populations: (1) expanded over vast continents, and (2) recovered from population bottleneck disasters imply that the potential for population growth was there, as far as the biological constraints on fertility are concerned. If local population growth wasn't happening through prolonged periods of time, it means that something was preventing it. The idea that it was stopped by humans somehow successfully coordinating to limit their fertility and avoid the tragedy of the commons strikes me as implausible to the point of absurdity, for the reasons already mentioned. There is no plausible way how such a state of affairs could have emerged, and even if it did, it could never be stable through any significant period of time.