Recalibrating Utopia:
I have mentioned before John Calhoun’s paper “Death Squared,” in which he described his experience in raising a large number of mice all in the same cage in Once Was a Utopia for Mice, but I continue to struggle with the implications. 

I expected that the time course of the mouse population would have two peaks.  It did not.  I suspected that this might have been due to Calhoun changing the way he counted his mice just when the first decline should have happened.  He started counting dead mice instead of live ones.  Maybe the mice were eating their dead compatriots.  But then the numbers should have gone up.  That could only have been through further births.  But the last surviving birth was on day 600 and the dip should have started about then.  He could hardly have missed it if further births had some later; it was exactly the kind of thing he was looking for.  So there cannot have been a second rise.

Sorry.  Didn’t happen.

The mouse plague statistics I sometimes cite show two different patterns: a single spike and a generally lower double spike.  I had thought the single spike was occurring when there was an enormous amount of interbreeding between local populations and the double spike was when the plague was natural increase in just one population.  The pattern Calhoun found was a single spike in a single population.  So I stand corrected. 

The single spike in the wild data seems to last a year and the double spike about two years.  But Calhoun describes two phases of growth, an initial exponential rise of 315 days and then a somewhat shorter growth period that was slower.  The frequency of counts of the plagues was not great, so the 315 is a year within the resolution of the data.  So if we assume that the mice in the plagues died out very rapidly – after all they were trying to survive in the wild – after their rapid growth slowed, then the results of the two kinds of study are the same.

But humans don’t face the hazards that wild mice do.  The opinion of those who have considered it is that neither predation nor limited food caused the decline.  That leaves them with disease as the only option; obviously they do not consider declining fertility, although that clearly happens in the Utopia study.

When we try to extend the pattern to humans, we use the captive mouse data, since that corresponds to the human condition to the best of Calhoun’s very capable ability.  We can pull out four numbers:

  1. Date of the start of the study.
  2. Date to the last live birth: 600 days.
  3. Time to menopause in female mice: he gives this as 560 days.
  4. Time for a mouse to have her first litter: something over 30 days; call it 40 days.

Then the numbers for humans ought to be:

    1) Time when middle class people stopped marrying even rather distant cousins.  This is highly problematic.  But the teachings of Eugenics, a now discredited field but once quite popular, include:
a) Don’t let the weaker reproduce.
b) Encourage the strong to reproduce.
c) Don’t mix “races.”
d) Never marry cousins.
The First International Genetics conference was held in 1912, so we take that as the kickoff.
2) Date of the last birth to the middle class, world over I should think: that’s what we’re trying to work out.
3) Time to menopause in women: we will take 40 as an approximation.
4) Time for a woman to have her fist child: let’s say 20 years.

The numbers here are pretty much related to women.  But Calhoun found that it was the males who were the disaster.  While things collapsed, the unmated females simply withdrew to safe corners.  The males either fought like crazy or spent all their time grooming.  It was the males that, when removed and placed with normal females, took no interest in reproducing.  But let’s see how it plays out. 

The time from menopause of the original females to last live birth is 40 days. 
By the time of last live birth the number of new generations that have been added is 600 divided by 40 or fifteen.  If you multiply 15 by 20 for humans, it comes out to 300 years; we should be all right until we approach the year 2212.

That contrasts with prediction reached by comparing the Mesopotamian experience of societal collapse within three hundred years and the founding of the US about 1776, which has our system unraveling in about 2076.  If one notices that the birth rate of middle class countries has been below replacement for about 30 years and the age at first marriage is rising inexorably, you come up with a comparable number.

So the mouse data seem rather equivocal.  But if you take the kickoff date for middle class people to be 1776, then it all works out quite nicely.  Sorry, that’s a poor word choice.

 But is collapse in 2076 plausible?  Men can be strong and active up until about 50.  That’s true for Russian men, who die shortly after, for NFL football players, who do the same, and for Harvard Medical School graduates – or so we were told, although I find it hard to believe as did the professor who said as much.

So if the last man reaches 50 in 2076 he will be born in 2026 to a woman who will be 40 at that time.  She will have been born in 1986 and now be 28.  Well there are women less than 28 having children, so no, it can’t be so.  But if you say that you need some men younger than 30, then she might be 8, and we have no idea whether girls younger than 8 will grow up to have children. 

So it’s too close to call.  Ten years from now it might be clear.

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