[ExI] re end of world

Anders Sandberg anders at aleph.se
Fri Sep 11 07:16:32 UTC 2015

On 2015-09-11 01:09, Rafal Smigrodzki wrote:
> Are you sure the variance would stay the same? Wouldn't removing 
> 99.9570883466% of the population from the reproductive pool lower 
> diversity?

Yes, but my crude simulation did not measure the variance decline. 
Obviously if we select just the two best individuals and have their 
offspring be the population diversity is going to be very small.

The selection formula states that R = h^2 S, where S is the difference 
in the mean trait in the selected parent generation to the population, 
h^2 is heritability and R the shift in new population mean. So for IQ, 
if S=150-100=50 and h^2=0.5-0.8 we get R as 25-40.

The variance change depends on the way the genes affect the trait, so it 
is not entirely obvious. If the population has no inbreeding, then 
removing X% of individuals will remove X% of all genes. If each gene is 
has a N(0,1) effect on the trait and there are M genes affecting the 
trait, we should expect the trait to be distributed as N(0,M). Removing 
X% doesn't change this, but the genes of different individuals now 
become correlated.

Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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