new start

On Wednesday 17 September 2003 16:53, Al Globus wrote:
(...)
> Apparently it takes about 20 generations for severe selection pressure
> to change a population. Unfortunately, I can't give references, but
> I've seen several discussions of different experiments that reached
> approximately this result.
(...)

If by "change" you mean "producing new caracteristics by mutation" then then
yes, it would take many generations.

However, if by "change" you mean "changing the frequency of alleles", then
with enough selection/pressure you can get substantial change in even ONE
generation.

For instance, suppose that you have a herd with black sheep and white sheep.
Suppose that, for some reason, you want just black sheep. You know the
Mendelian rules for determining the colors. Then you'll mate your sheep in
such a way that in the next generation there will be a predominance of the
black color.

As far as I have followed this rather off-topic thread about eugenics, you are
talking about changing the frequency of some caracteristics - intelligence,
it seems - in human populations. If you just want to increase the percent of
people with IQ above 130 then fine, probably you can do that in few
generations (because you would have just to manipulate allele frequencies);
but if you want people with IQ 500 (whatever that means) then you'll have to
wait for a looooong time (because you would have to produce a new species
with new genes, it seems).

Lucio Coelho