June 30, 2013
to be posted on nobabies.net

Luís M. A. Bettencourt
Santa Fe Institute
1399 Hyde Park Road
Santa Fe NM 87501

Dear Luís Bettencourt:
I read with interest your article (Luís M. A. Bettencourt The Origins of Scaling in Cities SCIENCE vol. 340 no. 6119 June 21, 2013 page 1438) and its review (Michael Batty same issue page 1418)  You demonstrate most elegantly how key parameters of cities vary in fixed linear, supra linear or sub linear fashion with great fidelity over several orders of magnitude.  I was much taken with your decision to describe the phenomenon as a network that serves to maximize energy flow rather than as natural networks do seeking to minimize energy flow.  And of course you went straight to the heard with your initial observation that the whole point of the city is social: people mix.

There is a parameter that one day you might pursue.  It is a failure rather than a triumph of the cities.  Cities don’t produce enough babies to endure: never have and unless there is some fundamental change never will be able to.  This observation is ancient and combined with the vision of a future in which we all live in cities gives one pause.

I once saw on the history channel (how one wishes TV could be conveniently referenced after the fact) that in ancient Asia Minor a barbarian once remarked to an urbanite that everybody who drank from a certain well became effeminate.  The rejoinder was nay, people who drink that water live in town, see the benefits of civilization and chose accordingly.  I wasn’t there, but I suspect “effeminate” meant at least in part not siring babies.  The ancient world collapsed, if we believe them for demographic reasons, and when cities arose again there was the belief that they were dangerous; people started carrying weapons.  Of course young men with swords will sooner or later play and sooner or later kill each other.  So I suspect police forces were set up to keep the peace.  Still not enough babies.  Still dueling fatalities.  Dueling outlawed.  Still not enough babies.  Concept of élan vial, some life force depleted in cities.  Concept disproved by Pasteur.  Lack of babies now blamed on infectious disease.  Infectious disease controlled.  Still too few babies.  And we are right back where we started with choice or pollution being fancied without real evidence.  Now we are losing the fecund country folk.  I seem to be the only one worried.

It’s really simple enough.  You don’t have adequate children unless you marry kin.  I’ve put evidence together on my web site
to no avail and even published a paper demonstrating the effect in fruit flies, which I attach.  In a manner of speaking I built a fruit fly city.  They survive but not in the numbers their environment could support and has supported at times.

Some day somebody is going to address this issue in cities.  Your model of the grand mix in which everybody has access to everybody else of course means essentially nobody marries kin.  While you are thinking about the structure of cities you might run across evidence for what I am saying.  If so, do not think you are going mad.  (Although until you see it in your own numbers doubtless you will think me mad.)  It happens and now you have access to data demonstrating it.

Really now, what do you think?


M. Linton Herbert MD

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