From: pockling@fraser.sfu.ca (richard pocklington)
Newsgroups: sci.bio
Subject: sexual selection
Summary: read about sexual selection
Keywords: peacock tails
Date: 18 Aug 92 20:49:12 GMT
Organization: Simon Fraser University, Burnaby, B.C., Canada

Female preference for male traits that may appear to decrease a male
animals survival ability is a well known phenomena.  A look through the
journal Behavioural Ecology will show many          papers on the subject.
A good point to get into the literature is Behavioural Ecology by JR
Krebs and NB Davies 1991 edition.  Both of these should be availiable at 
any good science library.  
To give you a quick overview, females have often be seen to use some 
criteria (many which at first seem arbitrary) to choose their mates.
Males are often less choosy, although in species where males make a
relatively large investment in mating (such as provisioning females
with a large nutricious sperm containing lump called a spermatophore)
they too may exercise mate choice.  In some other mating systems male animals
compete amongst themselves for access to females, or to territories or 
resources that females need.  
In many of these situtations there is directional selection for a certain
trait in males regardless of the other costs or benefits of that trait (such as long tails, bright colours or curly horns).  Once females begin to choose 
a certain type of male, the genes coding for the preference will become 
correlated with the genes that code for the male trait. 

mom with genes coding for a preference for trait 
                          +
dad with genes coding for such a prefered trait
                            =
offspring with both preference genes and trait genes
daughters express preference, sons express trait

This system can lead to the exxageration of the male trait.  How the system starts
is the real [problem, why on earth would females have an innate preference for 
peacock tails, or red bellies or some other silly acoutrement.
This is the point at which sexual selection becomes really interesting.

some current hypotheses are that some good genes (for strenght, spedd etc )
are correlated with the male trait, thus the silly trait started off as a 
marker for some trait and then got sweapt away on the tide of runaway sexual selection
Others think that males that survive with a handicap such as a long tail
must be more "fit" that those woithout, after all, they made it this
far with a huge honking nose, tail, antler rack etc.  they must have
some redeaming feature
The possibility that females have sensory or nervous systems that just 
happen to resond to ceratain wave lengths of colour or sound, allowing
males able to produce such wavelengths either through crosaking, singing or
waving coloured neck-flaps to gain a mating advantage.
One of the wierdest sexual selection hypotheses is that the male traits
somehow reveal information about parasites, this is a complicated one and
I won't get into it here.  

I hope this helps answer the question about peacock tails
            Richard Pocklington      Pockling@sfu.ca


since I haven't figuered out how to make up one of those funky 
sign off do-hickies everyone seems to have I will type one in here

  "Mom, how do volcanoes work?"
  "Why don't you ask dad?"
  "Awwww.  I don't want to know that much about volcanoes."
Newsgroups: sci.bio