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January 31, 2014 at 3:58 pm #7479John TavesParticipant
I totally agree with Paul Ehrlich that all population numbers must be headed down ASAP. I say this to make it clear that the following criticism of Ehrlich’s “Balancing Births and Deaths” paper is intended to show the flaws with the current wisdom of our population experts. I agree with Ehrlich that the Demographic Transition Theory is totally inadequate to provide hope that we will reduce our numbers via low fertility faster than the environment will reduce our numbers via premature death.
There is a subtle flaw with the following quote that shows a fundamental flaw with the conventional wisdom: “no known society has ever had its birth rate just balance the death rate for a substantial period and thus achieve a steady-state (“stationary”) population.” Ehrlich would have been more accurate if he had said that no known society has ever managed to limit their fertility such that their population remained stable and below the limits of the environment. (The inhabitants of the island of Tikopea in the Pacific as described by Jared Dimond in Collapse is one example of a society that did achieve this).
The human population history is dominated by periods of stable populations within each environment. The individual societies within those environments will grow and shrink over time as they compete among themselves. This stability is provided by the environment. If the environment is stable and the humans make no break throughs in technology, and the environment is large enough to support several societies, then the population numbers in that environment will be stable too. This is because we humans are like every other species in that we are always attempting to drive our numbers to infinity at an exponential rate. The environment stops that attempted growth.
Think of a bucket with a hole in the bottom. The amount of water in the bucket is the population. The water running out that hole represents old age death. Water running over the sides represents child mortality. The rate that we pour water into the bucket is how many children we are averaging. It is trivial to have a stable population, just keep the walls of the bucket at a set height. We humans, and all species, have always poured water into the bucket so fast that the bucket is always full and overflowing.
The flaw with the conventional wisdom is an unrecognized assumption in their thinking. Demographers assume that somehow child mortality is not affected by the birth rate. In a stable environment, and a population that is at the limit, the child mortality rate will be (x-2)/x where x is how many children adults average. (This is like mean water height of an ocean. You will almost never record that number but it must fluctuate around it.) The replacement rate is the child mortality rate, and notice the definition of replacement rate, that Ehrlich refers to in the article, does not attempt to ensure that x is not affecting the child mortality rate. The only way that the birth rate is not affecting the death rate is if the population is not at The Limit of what that environment can provide for or if that population is systematically controlling their fertility. No society, except the Tikopeans and now the Chinese, have controlled their fertility, thus there is no excuse to assume that we are not at The Limit.
There are several contributing factors for why demographers do not comprehend this, but I think the most important factor is that they use birth rate and death rate as defined as births/deaths per 1000. This measure obfuscates the magic number 2. It clouds who must die when we ram our numbers into the limit and continue to crank out babies too fast. Instead, they should use Average Number of Children. This is almost the same numerical value as TFR, but without the complicated definition. Average Number of Children is calculated by asking every adult, right before they die, how many children they created, and averaging that. This definition is easy for everyone to understand. It is trivial for one to determine their contribution and compare that to the magic number 2. This definition flawlessly isolates the deaths that are caused by averaging too many children, and clearly marks those deaths as premature deaths. Children and only children must die if adults average too many babies.
Another reason that demographers don’t recognize this is because there are many examples of societies that reduce their fertility. There are morality rules like, no babies out of wedlock and don’t have one if you are too poor to care for it. These do reduce the child mortality rate from what it otherwise would have been. However, only the Tikopeans put in place the correct morality that will allow them to reduce their fertility such that they knew that they were not suffering child mortality as a consequence of too many births. If I use the bucket/water example, then yes, many societies have reduced the inflow of water, but only the Tikopeans ensured that water was not flowing over the sides.
This must be taught. Every population expert needs to understand this and we need to move this information into the required curriculum for every child in the world.