Chapter 20

First Summary
There are two advantages of restricting gene pool size.

Urgent selection favors early speciation in turn limiting gene pool size.

Richard Sibly demonstrates a general principle dictating faster growth with smaller animal populations.

Helgason, drawing on Iceland population records, demonstrates higher fertility with closer kinship.

Rodrigo Labouriau draws on Danish data to show smaller towns and closer birth places correlate with more children irrespective of income and education. 

UN numbers show higher birth rates in less developed countries, more in moderately developed countries and least in most developed countries, and all lie exactly on the same curve of fertility against time. 

Captive fruit flies demonstrate an oscillating population size in the absence of any change in room, lighting or nutrition. 

A computer program models the same oscillation as demonstrated in the lab. 

European vole populations follow the same damped oscillation as lab fruit flies and the relevant computer program.

Historical record of regime survivals in Lower Mesopotamia shows all regimes collapsing from population size without regard to internal nor external factors. 

Pooling data from Roman regimes, classical Mayans and Anasazi shows the same pattern as Lower Mesopotamia.  Also, Egypt shows the same pattern except that there is selection at work early in the course of regimes, and a few regimes escape the brick wall crushing Mesopotamia. 

Civilizations in China defy the deadly 300-year barrier in Mesopotamia, but dynasties are destroyed right on schedule.

In Japan dynasties are somewhat less durable than in China, possibly because of powerful noble families, but on first inspection the time course is the same; later analysis proved this to be spurious.

Pre-contact subsistence farmers in the four corners region of the US had a population that flourished and then died out on the same time course as Chinese dynasties, an extreme example of income not determining fertility. 

Mouse populations in Australia show stable low densities like many animals, single cycle events like mice in a lab, and strengthening oscillation like human populations.

Bateson demonstrated that Japanese quails were attracted to moderately close kin, which is a new mating strategy which would confer a fertility advantage and can be compared with mating strategies in other species. 

Rich countries like Sweden have had populations that fell and superficially stabilized, but simultaneously have had an inexorable rise in age of marriage, foretelling an impending demographic disaster due to outbreeding, while autism possibly follows as well.

Virtual pre-zygotic, post-zygotic and combined curves square well with reality.
Lab work suggests that pre-zygotic and post-zygotic fertility regulation are both mediated by methylation, raising the question of whether current folic acid use is safe.
How odd.  This looks like the table of contents.

Chapter 21

Table of contents

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