[ExI] The Catholic Impact (was Re: Origin of ethics and morals)

[Anders Sandberg]

Hmm, what was the selection pressure from priestly celibacy? One source 
I glanced at suggested a density of 0.25% clergy, or one in 40. Assume 
that you need above intelligence to join the clergy: this means that the 
fitness of the smarter people will be 1-(1/40) (assuming they could keep 
it in their cassocks, which was not always true).

Now, intelligence is due to a lot of small gene components with overall 
heritability h^2=0.5 or so. In selection experiments h^2=(R-M)/(S-M), 
where R is the response in the population trait, S is the value it had 
in the selected parent population and M is the population mean. As 
parents for the next generation we have a population with mean 
intelligence S = 0.5*(100-12) + 0.5*(100+12)*(1-1/40) = 98.6 (the first 
term is the under iq 100 people, the second the slightly decreased 100+ 
population, and 12 is the expectation of a half normal distribution). So 
we should expect an IQ in the next generation of (98.6-100)*0.5 + 100 = 
99.3. Not much.

OK, lets make a recursion out of this. Let M(t) be the population mean 
smarts at time t, and assume it is always the upper half that has a 
chance of becoming clergy and that variances stay the same. S(t) = 
0.5*(M(t)-12) + 0.5*(M(t)+12)(1-1/40) = [(1-1/80)M(t) -3/20].

M(t+1) = M(t) + h^2 (S(t)-M(t)) = (1 + h^2 (1-1/80) -h^2)M(t) -h^2 3/20 
= 0.99375 M(t) - 0.075.

Not the nicest formula, and I might have slipped somewhere. But running 
this from M=100 at  the First Lateran Council (1123) to the present (36 
generations) produces an overall reduction of population IQ to 77.37. 
The present IQ of Italy is 102, so I suspect this overestimates the 
continence of priests, the selection effect, heritability and entry 
requirements to clergy.

-- 
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University