[ExI] IQ and beauty

[rex]

John Clark <johnkclark at gmail.com> [2015-10-08 09:13]:
>    On Wed, Oct 7, 2015  Dan TheBookMan <[1]danust2012 at gmail.com> wrote:
> 
>      ​> ​Well, an issue here is whether the particular trait or set of traits
>      is determined by a gene or set of genes in the first place.
> 
>    ​That would be a more complicated example especially if the various genes
>    were a long distance from each other on the chromosome, but the end result
>    would be the same because females who had a gene or genes for liking long
>    tailed males probably had a mother who also had a gene or genes for liking
>    long tailed males and probably mated with such a bird. Therefore a bird
>    probably has a gene or genes for both producing a long tail AND a gene or
>    genes for liking a long tail. And that is the recipe for a disastrous
>    positive feedback loop.  

Got an real example? I ask because it's easy to construct "just so" 
evolutionary arguments, but no so easy to find real examples, e.g., group
selection exists in theory, but the conditions required for it to work
are so restrictive that real examples are virtually non-existent.

>    Ronald Fisher ​, probably the greatest biologist since
>    Darwin, tested ​the idea ​with the African long-tailed widowbird ​
>    back in the 1930s​ . The tails of ​widowbirds ​of​ average length
>    (but still too long for ​optimal​ aerodynamics) were cut several
>    inches shorter and released back into the environment and their
>    behavior followed for many years. Just as predicted those
>    widowbirds lived longer than average but had fewer descendants.
>
>    ​It was also​ found ​that when ​widowbirds with unusually short tails
>    ​had​ artificial tails ​surgically attached to bring them up to
>    average length they didn't live as long as ​their​  fellow ​ short
>    tailed birds without the prosthesis but ​they ​had more descendants.
>    ​​And​ that too was as predicted. 

But it doesn't follow that this would lead to extinction. After a
positive feedback loop operates for a while it may alter the
environment in such a way that the formerly positive feedback is now
negative. Voila, you have semi-cyclic behavior instead of extinction.
There are many examples of semi-cyclic population levels, but extinctions?
 
>      ​> ​What I've heard used as an explanation is having a outsized tail
>      anving is kind of proof to the peahen that the peacock is fit overall
>      because a less overall fit male with the same large tail would likely
>      end up as dinner or otherwise in dire straits.
> 
>    ​Maybe, but for whatever reason the female is choosing to mate with birds
>    that have grossly un-aerodynamic tails, and that does not bode well for
>    the future of the species. 

In theory. 

-rex
-- 
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