#2. The Iatrogenic Conflicts of the Twentieth Century [population, engineering]

PO   EN

Red, theory; black, fact

Center: a centrifugal speed governor that would have been familiar in 1914. The Steam Museum, Kingston, Ontario

Medical Advances During a Turbulent Century

In 1911, the anti-syphilis drug salvarsan, invented by Paul Ehrlich, became widely available to the public, at a time when this disease was cutting a wide swath of morbidity and mortality. Three years later, World War I broke out.

In 1937, sulfa drugs, the first effective treatment for tuberculosis, became available to the public. Two years later, World War II broke out.

In 1945, both penicillin and streptomycin became available to the public, followed in short order by the first mass vaccinations, notably against smallpox. In that decade (1945-1955), the Cold War between the United States and the Soviet Union began. That one nearly finished us in 1962, the year of the Cuba Missile Crisis, when a nuclear WW III was narrowly averted.

A Possible Mechanism 

In the human brain, there may be a wholly unconscious controller for population density with a feedback delay of some two to four years, that answers every sudden downtick in the death rate with a brutal, reflexive uptick. Recently, these downticks in the death rate have been due to advances in medicine, hence my title for this post. "Iatrogenic" means roughly "caused by doctors."

Supporting Evidence

Moreover, last year I noted that the headlines were all about ISIS, an unusually disruptive phenomenon of the Muslim world. I then checked to see what the main preoccupation of the headline-writers had been exactly four years previously. This seemed to be the Arab Spring, when many old governments in the Arab world were being thrown off. I concluded that these regimes had somehow been suppressing population growth.

An Engineering Model

If this controller is real, it should be just as analyzable as Watt's steam-engine governor, using standard engineering approaches. If it has a significant feedback delay, then a perturbation sufficiently rich in high-frequency harmonics (i.e., sufficiently sudden) should drive it briefly into a damped oscillation.

Evidence for the Engineering Model

In support of these conclusions, here are the US Census Bureau statistics on the percent growth rate of the human population for the 20th century, international yearly figures, aggregated to "World," and extended back to 1900 with decade-wise World data from the historical estimates table. At roughly the end of WW II, there is a huge jump in the growth rate followed by a sharp drop bottoming at 1960, followed by another sharp peak at 1962, followed by a leveling off superimposed on a gradual decline, the latter possibly due to increasing absolute numbers. This time series could be construed as showing a damped oscillation. See below.

The historical global population growth rate scaled to population.

The surmise that the post-1964 decline in the plot would disappear if corrected for changing absolute numbers is confirmed by calculation based on US Census Bureau data. See below. Furthermore, the plot shown below appears to level off at 78 million new people per year, which is probably the upper trigger level for the controller. There is probably no formal lower trigger level, making this controller asymmetric. Oscillation begins well before this level is reached, however, indicating the possible presence of a differential control term. 

Other Features of the Data

The sharp upstroke in growth rate that occurs at 1980 may be due to the eradication of smallpox over the decade 1967-1977. The downturn after 1988 was probably due to the AIDS pandemic. The data are coarse-grained before 1950 and do not show the upstrokes in 1911-1914 and 1937-1939 that I would have predicted from the two world wars.

World population growth rates in persons per year with no scaling. Note the reaction in 1960.

Mechanism of the Putative Damped Oscillation

A scan of historical events for the period 1954-1960 turned up nothing notable except in 1957, the year the down-dip anomaly began. That year saw a flurry of atmospheric nuclear bomb testing, rocket development, and regime changes. Racial integration began in the USA. The dominant sentiment driving all these changes may have been: “We gotta protect the kids.” Of which there were quite a few. Perhaps the downturn in population growth lasted until parental concerns about security were allayed. In general, how does one provide security, universally desired but universally elusive? The matter may be complex and demand a formal science of security.

Had the issues simmering below the surface been different, the dominant sentiment may have been different, but the population growth curve reversal would have looked the same, being due to a child-driven loss of tolerance for problems previously tolerated.