September 7, 2012
to be posted on

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concerning: More or Less
ECONOMIST vol. 404 no. 8800 September 1, 2012 page 77

A mark of good journalism is being willing to emphasize an important issue that nobody else wants to touch, and you have done this in your report of the work of Anna Goodman.  You also get kudos for refraining from exaggeration; in fact you engage in understatement.  Goodman’s work indicates from information collected in Sweden that the demographic transition whereby richer people have fewer babies (and this effect increases with generations) makes little sense from a simplistic evolutionary perspective.  Received wisdom is that prosperous people have fewer babies but invest more in them, enhancing their reproductive chances. Goodman finds that indeed those children do well, but their own children are fewer than the average for the grandchildren of poorer people.  Since the birth rate for Swedish born women is about 1.81 – below replacement – rich Swedes must have a birth rate below that. 

Of the theories of evolution my favorite is Aristotle’s: Things happen by chance, and what works may persist.  On the face of it, a persistent birth rate so low must be accomplishing one thing: the erasure of the population.  Why this had to evolve is a little subtle.  Speciation is vital to any form, since things always change and a new niche cannot be optimally exploited unless some existing form can bud off a new species to specialize in it. 

Let’s say it takes 2,000 years for speciation to occur.  Two critical chromosomes that have been in mutually isolated gene pools for that long cannot have fertile offspring when they are reunited.  But if the population size is 1,000 randomly mating individuals, it still takes about 2,000 years for them to get together.  The population dies.  This obviously does not work, and accordingly nature has allowed a mechanism to emerge that does a running census.  If the kinship of a couple is too low, so is their fertility.  This eliminates a local population in about 10 generations but permits the species at large to survive. 

Rich people have a wider social horizon than those in the tiny bands in which we evolved and rich people frequently take advantage of their opportunity to marry outside the local group of under 1,000.  As you point out, no individual suffers at first.  But eventually there will be demographic changes so severe and destabilizing that everybody will suffer.

One would think that courtesy would require warning folks. 


M. Linton Herbert MD 

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