August 14, 2012
to be posted on

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I am most happy that it appears you have a new column “Baby monitor” (ECONOMIST vol. 404 no. 8797 August 11, 2012 page 67).  Well done.  The issue is so important it does merit your move.  I shall try to curb my enthusiasm and not chatter on for ten pages.

I did notice that while it is by now a truism that when people are making financial choices they do not act as rational agents.  It is also widely felt that in politics people do not act in their own rational self interest.  For instance on page 46 you mention that the cultural wishes of voters are anxieties to be calmed rather than legitimate demands to be addressed.  But when it comes to love and children your Baby monitor column presents people as the ideal of ratiocination.  Nothing if not imaginative, are we?  (I intend no reference to page 56.)

When people abandon reason, their actions become hard to predict in investment strategy and in politics.  But in reproductive issues there is a better rule than even rational choice, which after all is hard to analyze.  Young hands may help on the farm, but are they really cheaper than hired help?  Adults deliver more work per calorie consumed (they aren’t growing) and need less supervision (they have experience).  Perhaps children are to be the providers for the parents in old age, but the value of that must be compared with the cost and discounted at a rather high interest rate.  I don’t even know any anthropological studies that offer hard numbers, much less subsistence farmers. 

When one gives up rationalizing reproductive events, there is a very good alternative.  It’s all consanguinity, what Patrick Bateman has called “optimal outbreeding.”  The same pattern is visible in animals (On the Regulation of Populations of Mammals, Birds, Fish and Insects, Richard M. Sibly, Daniel Barker, Michael C. Denham, Jim Hope and Mark Pagel SCIENCE vol. 309 July 22, 2005 page 609) and in humans (An Association between Kinship and Fertility of Human Couples Agnar Helgason et al. SCIENCE vol. 329 no. 5864 February 8, 2008 page 813 – 816 AND Human Fertility Increases with marital radius. Rodrigo Labourian and Antonio Amorim.  GENETICS volume 178 January 2008 page 603 AND Comment on “An Association Between the Kinship and Fertility of Human Couples,” Rodrigo Labouriau and António Amorim SCIENCE vol. 322, page 1634b December 12, 2008)  With that much evidence this is not a curiosity.  This is a law of biology. 

Good luck with the new column.  I hope you find occasion to see how the interplay between consanguinity, fertility, demographics and history plays out. 


M. Linton Herbert 

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