[gurps] BioTech-- Eugenics Question

[Wyrm]

midnightwind at comcast.net wrote:
[snip]
> One question that might help-- does anyone know approximately how many generations it takes for a beetle species to go from flight to flightless when placed in an environment that is highly selective against flight, for example?  Does that number even come close to modeling a similar circumstances in humans?  How quickly would I have almost all 7-foot humans if we only allowed seven-footers to reproduce with each other, and nobody else?  Is it 1-2 generations, or 10, or more?  I think probably only 1-2, to be honest.  But, that's why I'm asking-- and a collection of attributes is a lot more complicated...
> 
> Anyway, thanks for the insights...
> 
> -vk

It would entirely depend on the incidence of beetles currently born 
flightless the nature of the air born threat, when in the life cycle 
they begin to breed (i.e. before or after they fly), and why they fly in 
the first place.

If flight=death and they do not breed first... the population will 
approach zero rapidly. Now IF there are flightless reproducers (some 
wingless recessive mutation) they will become more dominant in the 
population.

If they breed before flying the population has no reason to change... 
reproduction has occurred and the adults are now expendable. There might 
even be a population boom if the as yet flightless young had to compete 
with the now vanished adults for food.

Any lasting change is going to take several dozens of generations at 
LEAST, unless there is some dramatic overwhelming mutation that gives 
one gene line a massive breeding advantage.

Do not forget that many insect families have many complete generations 
in one of our years and a change like this only seems rapid to us.

There is a pod cast on silent crickets in the Hawaiian islands where a 
predator exists that is drawn to the mating call of the males with 
"normal" squeaky wings.

http://www.cbc.ca/quirks/archives/06-07/sep30.html
Scroll down to "quiet crickets".