From: andrick@sun.rhrk.uni-kl.de (Ulf Andrick [Biologie])
Subject: Re: sexual selection
Keywords: peacock tails
Reply-To: andrick@sun.rhrk.uni-kl.de (Ulf Andrick [Biologie])
Organization: University of Kaiserslautern (Germany)
Date: Tue, 1 Sep 1992 18:20:13 GMT

In article <1992Aug24.125723.139700@rrz.uni-koeln.de>,
aeg03@rrz.uni-koeln.de (Jan T. Kim) writes:
> In <94338@bu.edu> colby@bu-bio.bu.edu (Chris Colby) writes:
> 
> >In article <josh.714267691@mowgli> josh@cqs.washington.edu (Josh
Hayes) writes:
> 
> >>The trait cannot go to fixation unless
> >>there is a correlation between the advertisement and the property
> >>advertised.
> 
> >Sure it can, the fitness boost due to sexual attractiveness can
> >overshadow the fitness loss with regards to survival. There's a
> >paper by Lande that models the population genetics of this, I
> >believe. I'll look it up later (I can't right now or I would.)
> 
> Obviously, if the females favor males with any  arbitrary  trait,
> this  male  trait  can  be fixed if it adds to the overall mating
> success (i.e. if the  males  with  the  trait  can  produce  more
> offspring in their shorter lives than those without the trait can
> in their longer lives).
> However, it seems to me that the female trait to select for  such
> males cannot be fixed if you start with a population with females
> indifferent towards this trait.  Then,  if  females  appear  that
> prefer  males  with some trait that lowers their survival chances
> their (male) offspring will be less fit  than  the  offspring  of
> those females that don't care about the trait.
> So, how could the female preference for males with  funny  traits
> evolve?  I  think  the  answer to this question is the key to the
> understanding of the evolution of  the  funny  male  traits  too.
> Some ideas [deleted]

I think that this `prima causa' which makes that all those signals
have not vanished, though they impose a handicap onto the individuals,
is the need of finding and recognising* some mature partner at all, 
apart from the problem which one is the best. This might be a trivial
idea, but it seems to be a little neglected in the whole discussion.
Note that the task of recognising objects, as performed by the central
nervous system, is NOT trivial. 

Seeing some of the wild speculations on how certain traits might 
indicate a good genome, I wonder if there is not sometimes too much 
significance attributed to the selection by the partner.
In species with sexual or permanent territoriality of the males,
it might be more important who gets the best territory, i. e. that
one where females are most likely to appear, than a selection
performed by the females. In social species, ranking systems may
provide for a selection more than the females. The female
recognition mechanism needn't be optimised to recognise the best 
partner. E. g., the female might be attracted by an especially 
conspicuous male, but then mate some less attractive sattelite
lurking about near the territory owner.

Such a small selective pressure on the female recognition system
may allow that it responds to an over-optimal stimulus more than
to the normal habitus, which has to evolve towards a compromise 
between attractiveness and usefulness for survival.
 

Footnote:
* Martin Luther uses the verb `erkennen' (to recognise) in his bible
  translation when referring to the sexual act. This gives the `tree
  of recognition', the fruit of which Eve offers to Adam, a special 
  meaning, which one would not think of first. Is this the same in 
  the English version of the bible? 




Ulf R. Andrick                                  andrick@rhrk.uni-kl.de
Tierphysiologie
FB Biologie
Universitaet
D-W 6750 Kaiserslautern