Collapse of Complex Societies, byTainter - Roman, Mayan, Chacoan:
Someone prompted me to read this book (The Collapse of Complex Societies.  Josheph A. Tainter.  Cambridge University Press.  Cambridge.  Eighteen printing, 2009) suggesting it might have valuable data.  It certainly does.

Tainter is interested in collapse, as his title indicates.  In the book he considers a number of explanations that have been entertained in the past.  One he quotes is by R. H. Towner, who postulates something to the effect that mothers of geniuses tend to be frigid and that when social growth means they are no longer required to have children the geniuses cease to appear and the civilization dies.  I hope Towner is wrong, because it will require a genius to make public what I am telling you, and nobody ever thought my mother was frigid.  Towner does, however, seem to have got the point that babies might have something to do with social survival.

For Tainter, the central issue is that a society, a civilization, is a problem solving machine.  And it has to function.  It must be able to put the goods on the table.  Over time, stresses of infinite variety require that the society keep developing new administrative protocols, increasing its complexity to the point where the society perishes.  This is analogous to my own argument that genetic complexity can only be increased within finite bounds, and I am quite sympathetic with his arguments generally.  One thing I noticed was that from time to time he mentions almost parenthetically that the birth rate of some society or a key component of the society fell.  It makes me think of a grade D movie in which a man is skulking through a cemetery hiding from the police and from time to time peers over his shoulder wondering what that slobbering sound is.

Tainter’s main focus is on Rome, the Mayans and the inhabitants of Chaco Canyon, each group having accomplished impressive things in terms of mass organization and construction.  I have never analyzed them because no single one seemed to have undergone enough cycles to make a statistically interesting result.  So I propose to lump them together.  He gives useable dates for the Mayans and Chacoans.  For Rome he just gives the dates of emperors, which does not help, so I must turn elsewhere for data about Rome. 

For Rome, I have taken the BBC timeline, choosing the years in which there was a major change in regime, not that things were often tranquil in between. 

BBC Ancient Rome Timeline

By Dr Dominic Berry

Foundation of Rome, 753 BC to expulsion of kings and founding of republic, 509 BC to end of struggles with patricians, 287 BC to first emperor 27 BC, citizenship extended to all free inhabitants of empire, 212 AD to capital moved to Constantinople 324 AD, fall of western empire. 476 AD. 
244, 260, 239, 112, 152.

The Lowland Classic Mayan dates are on page 153.  Protoclassic, 50 BC – 250 AD Early Classic 250 AD to 550 AD, hiatus, 550 AD – 600 AD Late Classic 600 AD – 800 AD Terminal Classic 800 AD – 1000 AD.
300, 300, 50, 200, 200.  The rounding to the nearest 50 years has already been done for us.

The Chaco Canyon dates are on page 180.  When a range is given, we choose the last date of the range.  Basketmaker III, 500 AD – 750 AD Pueblo I, 750 AD – 900 AD Early Pueblo II 900 AD – 1100 AD Late Pueblo II, 1000 AD – 1050 AD Early Pueblo III, 1050 – 1150 AD Late Pueblo III, 1150 AD – 1225 AD.
250, 150, 200, 50, 100, 75. 

At a glance we can see that the Roman and Mayan regimes averaged about 200 years in longevity while the Chaco Canyon periods last about 100.  I suspect that means we should not be splitting Pueblo II and Pueblo III, but since early and late Pueblo II overlap it is not clear how to lump them.  At all events, here is what we get when we group all three together and graph the results.




Experience of survival Roman, Mayan and Chaco Canyon regimes lumped together. 

The shape of the curve is much like the curve for Mesopotamia.  I suppose that before any group emerged as dominant in any of these societies it already had a history of being a significant sized population with mutual socialization.  At all events, the line adds further evidence, if it were needed, to the effect that urban civilizations in any century and on any continent face a single dominant threat.  The only such threat must be demographic, must in fact be a lowered birth rate and this infertility can only be because of the genetic effect of a large gene pool. 

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