[extropy-chat] Why Progress Might Slow Down

[Robin Hanson]

[Hi folks.  I've been off the list for a while, but thought I'd rejoin in 
order to mention
the following interesting development.  RH]

The human race has made tremendous progress in the last century, and 
honestly there's a lot
we don't know about how this has been possible.  In particular IQ scores, 
lifespans, and many
other things have been improving at rates we do not really know how to 
explain via the
usual suspects.

I've just been made aware of the following paper, that suggests many of 
these improvements
have been driven by travel and urbanization induced wider mixing of human 
mates, which
reduces the expression of recessive alleles.

It is at least a plausible theory, and it has the clear implication that 
these improvements
will run out as the population approaches "panmixia".  Progress might then 
continue, but at
a slower rate than it otherwise would.  (Even so, of course, other kinds of 
progress may make
growth rates then higher than now.)

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http://www.dienekes.com/blog/archives/000354.html

The secular rise in IQ: Giving heterosis a closer look
by Michael A. Mingroni, forthcoming in Intelligence

Although most discussions today start from the assumption that the secular
rise in IQ must be environmental in origin, three reasons warrant giving the
genetic phenomenon heterosis a closer look as a potential cause. First, it
easily accounts for both the high heritability and low shared environmental
effects seen in IQ, findings that are difficult to reconcile with
environmental hypotheses. Second, numerous other highly heritable traits,
both physical as well as psychological, have also undergone large secular
changes in parallel with IQ, which is consistent with the occurrence of
broad-based genetic change like heterosis. And third, a heterosis hypothesis
for the trend can be tested in several straightforward ways. The paper also
provides a hypothetical example, based on data from a real population, of
how heterosis can result from demographic changes like those that have taken
place throughout the developed world in recent history and shows that under
certain conditions, even a small demographic change could cause large
genetically based phenotypic changes.
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Robin Hanson  rhanson at gmu.edu  http://hanson.gmu.edu
Assistant Professor of Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030-4444
703-993-2326  FAX: 703-993-2323