Particle physics experiments

the real rats of the NIMH


I first read Mrs. Frisby and NIMH Rats as a young person. What I didn’t know at the time was that he was inspired by a series of experiments on population dynamics from the 1940s to the 1970s.. The two studies, lasting a total of eight years, aimed to explore the effects of population density on behavior.

John B Calhoun was a behavioral researcher and ethologist who spent most of his career at the American National Institute of Mental Health (NIMH) in Maryland. His work spans six decades, from the earliest experiments with rodents in the 1940s to his death in 1995. But he recently rose to fame for his work in 1958-1962, starting with a quarter-length enclosure. acre of wild brown rats and a 1968-1972 experiment with mice called Universe 25. Universe 25 was his pinnacle of research – a “rodent utopia.”

Calhoun calculated that his enclosure of wild brown rats (or brown rats, aka Parisian rats, Hanover rats, street rats, common rats, sewer rats, dock rats … 5000, but the population strangely never exceeded 200. With extremely high infant mortality rates, by the end of the 27th month of observation, the population had stabilized at 150 adults.

Calhoun and his team were surprised by these unexpected results and therefore embarked on a more controlled experiment involving a population of domesticated brown rats, conducted in a converted barn (a luxury for the animals).

Calhoun’s new rat palace consisted of a 3m x 4.3m room, divided into four enclosures by an electrified fence. These enclosures contained everything a rat could need: food, water, raised burrows, spiral staircases, nesting boxes… a rodent wonderland. The ramps connected pen 1 to pen 2, 2 to 3 and 3 to 4, but not pen 1 to pen 4. This meant that the rats tended to concentrate in pens 2 and 3, leading to the development of what Calhoun dubbed a “behavioral sink”: a kind of voluntary overcrowding that resulted from the initial, unintentional overcrowding, and led to significant changes in the behavior of the rats.

These changes were not on the right side of the scale.

In male rats, behavioral disturbances ranged from “sexual deviation”, cannibalism, and frenzied hyperactivity to pathological withdrawal.

Due to the congregation of the population in the middle enclosures, the rats have become unusually accustomed to the presence of others. Eating and engaging in other “biological activities” have been transformed into social activities, which they would only do in the presence of other rats. While this is great for eating (who doesn’t like dinner?), It disrupted the sequence of other normal activities, such as courting, building nests, and nursing and caring for their young.

In the rats most affected in a series of these experiments, infant mortality reached 96%. In male rats, behavioral disturbances ranged from “sexual deviation”, cannibalism, and frenzied hyperactivity to pathological withdrawal.

Now decades into his rodent studies, Calhoun’s goal had evolved into lifespan extension by creating a “death-inhibiting environment for mice,” also known as Universe 25. Universe 25, like Calhoun’s ornate rat barn, was created to cater to little experimenters in every way. The 2.7m x 2.7m metal enclosure featured 16 vertical lattice tunnels, each with four horizontal corridors opening at the top, and each corridor leading to four nesting boxes.

With each of these 256 nesting boxes being able to house up to 15 mice, Universe 25 was theoretically capable of accommodating up to 3,840 mice. (I know what you are thinking right now: “I bet not.” Neither do I, dear reader.) And, of course, there was an abundance of fresh water, food, and nesting material.

This is where it all starts to get a little… biblical.

John Calhoun with one of his rodent experiments. Credit: Yoichi R Okamoto, republished by the National Institutes of Health (NIH), via Wikimedia Commons.

Calhoun’s reduction in mouse mortality was based on identifying the rodent equivalent of the four mortality factors listed in Revelation – as in the Book of Revelation. Calhoun described the results of the Universe 25 experiment in a journal article titled “Death Squared: The Explosive Growth and Demise of a Mouse Population”. His text included a large number of biblical references to something published in the Proceedings of the Royal Society of Medicine.

Its first paragraph ends thus: “This brings us back to the first white horse of the Apocalypse who, with his rider, set out to conquer the forces which threatened the spirit of death. Further on in Revelation (ii.7) we note: “To him who overcomes, I will give to eat the tree of life, which is in the paradise of God” and further (Rev. xxii.2): ” The leaves of the tree were for the healing of the nations.

So in addition to its abundance of resources, Universe 25 was cleaned out every four to eight weeks, contained no predators, kept its temperature at a delicious temperature of 20 ° C, and was colonized by the best disease-free mice. Selected by the National The Institute of Health’s Breeding Colony. The only limitation was space.

Unfortunately, the result was a new, turbocharged rat barn. The population of Universe 25 began to grow steadily from the original four pairs of mice, until it reached a population of 2200 by day 560. At what point the population began to decline, and at what point the population began to decline. end of the experiment (day 1500), there were only 27 mice left. The last surviving birth was on day 600, after which the incidence of pregnancies declined very rapidly with no young surviving. The last conception took place around day 920.

While the dominant males first prospered and fathered all the offspring they could muster, the less dominant were inactive and eventually became violent towards each other. Those who were attacked would later attack others. The female counterparts of the withdrawn males simply hid. Females nursing in the presence of territorial males began to show aggression, attacking and injuring their own young and forcing them out of the nest before weaning was complete.

The next generation of mice, never having experienced healthy mouse behavior, had no concept of mating or parenting, or even territorialism.

Therefore, the next generation of mice, never having experienced healthy mouse behavior, had no notion of mating or parenting, or even territorialism. Some – dubbed the “prettiest” – spent their time eating, drinking and grooming in isolation. Elsewhere, mice have formed gangs of cannibalistic looters and rapists.

Gradually, with a cohort of mice no longer actively mating or constructively engaging in society, the population died out.

Calhoun worried not only about the death of the body (the second death) but also about the death of the spirit (the first death – see Revelation II: 11) – an unusual inclusion in an academic article. His thoughts are summed up in an equation of words, the penultimate entry in the article:

Mortality, bodily death = the second death
Drastic reduction in mortality
= death of the second death
= death squared
= (death)2
(Death)2 leads to the dissolution of social organization
= death of the establishment
Settlement death leads to spiritual death
= loss of capacity to adopt behaviors essential to the survival of species
= the first death
(Death)2 = the first death

I’ve been thinking about this equation for a while and have some issues from a freshman algebra perspective.

Let’s say that mortality (bodily death) is a function called M. Now, as previously stated, according to Calhoun’s article, there are five factors of mortality in the ecology of animals in the wild: emigration, scarcity of resources, inclement weather, disease, and predation. Mortality would therefore be a function of these factors: M = M (e, rs, wI, d, p). Now, the death of the second death would be the composition * of M with M, which we denote by M ?? M. (* Function composition is when you apply one function to the result of another: for example, if f (x) = x + 1 and g (x) = x3, then (F ?? g) (x) = f (g (x)) = f (x3) = x3 +1.)

This is where we run into a problem, because if we assume that M is a function of real variables, what we are looking at is the composition of a multivariable function with a multivariable function, which is technically not possible.

Calhoun believed that the death of the spirit, which here equates to social collapse, is unequivocally linked to the literal end of life.

But I digress. I think the most that can be concluded from this is that Calhoun believed that the death of the spirit, which here equates to social collapse, is unequivocally related to the literal end of life. That is to say: “The loss of these respective complex behaviors means the death of the species. Unfortunately, he also concludes that “for an animal as complex as man, there is no logical reason why a comparable sequence of events should not also lead to the extinction of species.”

Many scientists then and since would disagree with the somewhat gruesome conclusions of the experiment, arguing that Calhoun’s work was not necessarily about population density per se, but rather social interaction. . And humans interact with each other differently than rodents. As a result, “Death Squared” is cited primarily in work on laboratory rodents and rodent populations, rather than in research projecting the collapse of mankind.

Perhaps Calhoun himself tried to soften his conclusions. At the end of the few pages of biblical gloom in “Square Death”, he again relied on the Bible for the article’s last passage:

“Happy is the man who finds wisdom,
And the man who gains understanding.
Wisdom is a tree of life for those who
get hold of her.
All its paths lead to peace.
(Proverbs iii. 13, 18 and 17, rearranged) ”