I was reading a little bit about a social experiment a scientist did with some mice. I find it hard to believe that he reported on it accurately. He provided them with an ideal environment and at the beginning of the experiment the population peaked, he described all kinds of bad behaviors they developed, and they stopped reproducing and eventually almost all of them died out. Why would they have not reverted back to normal behaviors as the population density declined?
Could you please provide a link to this experiment?
I went googling and found a couple of links.
The first article seems to answer your question:
Not a lot of details in the links but it sounds like a population density problem. Unlimited food and water assumes those are the only needs animals have. Density problems with livestock show up with behavioral problems and I think I remember something about swine starting to bite at the ears and tails of their fellow future pork chops when kept in too tight of a space despite otherwise ideal conditions. It also sounds eerily like the mythological Mouseville in the Green Mile. Nonsense performed in the name of science is nothing new.
Speaking of nonsense,
Death Squared: The Explosive Growth and Demise of a Mouse Population
by John B Calhoun MD
(Section on Behavioral Systems, Laboratory of Brain Evolution & Behavior,
National Institute of Mental Health,
9000 Rockville Pike, Bethesda, Maryland 20014, USA)I shall largely speak of mice, but my thoughts are
on man, on healing, on life and its evolution.
Threatening life and evolution are the two deaths,
death of the spirit and death of the body. Evolution, in terms of ancient wisdom, is the acquisition
of access to the tree of life. This takes us back to
the white first horse of the Apocalypse which with
its rider set out to conquer the forces that
threaten the spirit with death. Further in Revelation (ii.7) we note: ‘To him who conquers I will
grant to eat the tree’ of life, which is in the
paradise of God’ and further on (Rev. xxii.2):
‘The leaves of the tree were for the healing of
nations.’
This takes us to the fourth horse of the
Apocalypse (Rev. vi.7): ‘I saw … a pale horse,
and its rider’s name was Death, and Hades
followed him; and they were given power over a
fourth of the earth, to kill with the sword and with
famine and with pestilence and by wild beasts of
the earth’ (italics mine). This second death has
gradually become the predominant concem of
modern medicine. And yet there is nothing in the
earlier history of medicine, or in the precepts
embodied in the Hippocratic Oath, that precludes
medicine from being equally concerned with
healing the spirit, and healing nations, as with
healing the body. Perhaps we might do well to
reflect upon another of John’s transcriptions
(Rev. ii. 1): ‘He who conquers shall not be hurt
by the second death.’
Back to the OP’s question as I understand it …
If you assume all mouse / rat behavior is utterly instinctive then you’d expect that as population declined from crazy-making crowded, the animals would revert to the instinctual behaviors appropriate to the more normal density. Even if the older rats/mice did not, their offspring would robotically follow their instinctual programming appropriate to the density they grew up in. etc.
If we assume instead that at least some behaviors are learned, that as social animals they are “raised” by their community of older animals, if not by their two particular bio-parents, then it makes sense that as the population dclines the newborns will be being socialized by older animals from the crazy era.
Given enough time equals enough generations of animals, could the community regenerate a more “normal” rat / mouse society? Sure, at least in principal. Social norms are as subject to evolution as are genetics. There’s no guarantee the animals would regenerate exactly the same society as one that never went through the crazy-making population boom. But since rat/mouse genetic nature is slow-changing, we’d expect to find their eventual social arrangements, once stabilized, would be not too far off from other colonies raised in isolation.
But what if the population decline turns into a crash? Below a certain number of animals, they don’t get the chance to have all the additional generations it takes to regenerate a society.
Is any of the above factual? I don’t know for certain. But I find the idea that rats / mice are utterly robotic instinct-followers per my first paragraph highly unbelievable. For insects or amoeba? Sure. For mice / rats? No way. Which makes the rest of my surmise really the only logical alternative; the rest is details.
I’ve often commented about humanity that all it takes is for one entire generation not to be taught to read, and all our accumulated knowledge will be lost forever.
As a thought experiment of course it depends on an unrealistic exaggeration. But it concisely points out that we’ve built a lot of layers of civilization atop the raw material of “human nature”. And all of that could be stripped away by a big enough cataclysm, leaving a very different sort of humanity in its wake.
Many species of animal have been observed to exhibit culture, i.e. behaviors that an individual learns from its social group (as opposed to behaviors that are transmitted genetically, i.e. instinct). Rats have made it onto the list:
If rats exhibit culture, then it seems likely that mice do too.
When certain rules are placed within a society and this results in societal norms changing and those rules are enforced over multiple generations, even if the rules are lifted the societal norms will continue to exists it may take something else to force the societal norms to change.
Example: China’s one child policy which began in 1980 that limited families to only having one child. This was enforced with monetary fines, withholding of government benefits and in many cases forced abortions. This policy continued til 2016 (36 years) when the government permitted families to have two children. However, birthrates did not increase. So China increased the policy to permit three children per family in 2021, and eliminated the fines for families that exceed the limit. The birth rate in China has continued to fall at about 2.2% per year since 2016. It has become a societal norm to have only one child, if you are going to have a child at all.
If China wants to see their population increase, they are going to have to offer incentives to have more children, or punishments for having so few children.
Good example. Thank you.
Another possible factor in China’s situation is the decline in birthrates seen in every society as it urbanizes and enrichens itself. Pre- the one-child policy, most Chinese were peasants, where more kids = more security in old age. Now that the policy has been rescinded, one heck of a lot of Chinese are (sub-)urban. And especially the folks in the prime childbearing age range. Children in that scenario are much more a cost- and hassle-center for you now than they are a retirement elder-care asset for future you 40-60 years later.
Or at least that’s what’s been seen in nearly every industrializing / urbanizing society for the last 150-ish years.
That’s not meant to pooh-pooh your point that social norms a) evolve, and are b) sticky. I’m just pointing out another way in which the Chinese government are trying to push a string here and will need big incentives to make it work.
This experiment came up in a web comic ( Freefall, if you must know). I’d never heard of it except indirectly, since I’d heard the results discussed before. Anyway, I got to wondering: Has anyone tried to reproduce it?
John Calhoun designed several artifical environements for mice and rats, if that counts as replication. Here is a recent article from The Guardian about Universe 25:
I don’t understand what is so hard to believe about his findings: the offspring of people affected by severe trauma exhibit the influence of that trauma in their behaviour and it shows in their biochemistry. Cite, one of many. Just search for “epigenetics of holocaust survivors” if you want more.
No it doesn’t. Replication means some other researcher performs the same experiment to see if they get the same results.