The Roman Philosopher Lucius Anneaus Seneca (4 BCE-65 CE) was perhaps the first to note the universal trend that growth is slow but ruin is rapid. I call this tendency the "Seneca Effect."

Monday, February 27, 2017

Another Seneca Cliff: The "Mouse Utopia"

Image courtesy of Hans Pelleboer. This is a screenshot from Dr. Calhoun's `Mouse Utopia' experiment from the 1960s Abscissa; time in days, Ordinate: Log N population.

In Calhoun experiment, rats were confined in a finite physical space, but they were always provided with sufficient food. The result was a growing population density that eventually led to disaster. Here is how Calhoun describes his results (Calhoun, John B. (1962). "Population density and social pathology". Scientific American. 206 (3): 139–148.)

Many [female rats] were unable to carry pregnancy to full term or to survive delivery of their litters if they did. An even greater number, after successfully giving birth, fell short in their maternal functions. Among the males the behavior disturbances ranged from sexual deviation to cannibalism and from frenetic overactivity to a pathological withdrawal from which individuals would emerge to eat, drink and move about only when other members of the community were asleep. The social organization of the animals showed equal disruption. [...]

The common source of these disturbances became most dramatically apparent in the populations of our first series of three experiments, in which we observed the development of what we called a behavioral sink. The animals would crowd together in greatest number in one of the four interconnecting pens in which the colony was maintained. As many as 60 of the 80 rats in each experimental population would assemble in one pen during periods of feeding. Individual rats would rarely eat except in the company of other rats. As a result extreme population densities developed in the pen adopted for eating, leaving the others with sparse populations.

[...] In the experiments in which the behavioral sink developed, infant mortality ran as high as 96 percent among the most disoriented groups in the population.


  1. Quite an interesting post Ugo. I found the behavioral sink especially interesting since a similar phenomenon seems to be developing across the world with populations and economic activities disproportionally concentrated in a small number of privileged urban centers with the rest ( urban + rural ) being allowed to decay. These centers also show extremely low fertility rates, most often <1 child per family.

    That is also seen in decaying empires, examples: Byzantium were the remaining life of the empire drained into Constantinople, Heian Japan were everything flowed into the court at Kyoto and the Western Roman Empire where the Emperor had become little more than the mayor of Ravenna while the rest the empire had passed on to forces under little more than nominal allegiance to the Empire.

    Some months ago I read an article saying that 60% of job creation in the USA was confined to just 20 counties were privileged urban centers were located.

    I would seem that today's "World Cities" are where modernity is going to die and be buried...

  2. Unfortunately, your graph is inaccurate and does not adequately describe the "kill-switch" phenomenon that Calhoun discovered, although he never realized it himself. His "mouse universe" study was published in 1973 and the sinusoidal population graph includes this notation at the apex: "Last Born, 1Mar,1970". THE ENTIRE COLONY BECAME EXTINCT FROM THAT POINT FORWARD. The same neuro-endocrine based population density stress effect is well underway in crowded human populations, as the comment above indicates. Calhoun thought the limiting effect was simply a breakdown of parental behavior, but we have a built-in population control mechanism, which he discovered in his mouse universes, but he did not know it. J.J. Christian accurately described this mechanism in his work and publications parallel to Calhoun's. We are headed for a human extinction event in about 120 years. Stress R Us.

    1. Thanks for your interest and please don't take this post as anything more than a simple note on this phenomenon based on something that I found on the web. I don't pretend to be an expert, here, and if you have comments more extensive than this one, I would be interested in publishing them in this blog.