Path: utzoo!mnetor!uunet!husc6!uwvax!dogie!uwmcsd1!ig!agate!saturn!chromo!kevin
From: kevin@chromo.ucsc.edu (Kevin McLoughlin)
Newsgroups: sci.bio
Subject: Re: Sexual selection
Message-ID: <2418@saturn.ucsc.edu>
Date: 18 Mar 88 21:46:48 GMT
References: <1566@mmm.UUCP> <3138@arthur.cs.purdue.edu> <1164@microsoft.UUCP> <2402@saturn.ucsc.edu> <4776@ecsvax.UUCP>
Sender: usenet@saturn.ucsc.edu
Reply-To: kevin@chromo.UUCP (Susan Nordmark)
Organization: Physics Asylum, University of California, Santa Cruz
Lines: 35

In article <4776@ecsvax.UUCP> hes@ecsvax.UUCP (Henry Schaffer) writes:
>...
>> Susan Nordmark writes:
>> So dimorphism MAY be a result of direct female choice for big males
>> but PROBABLY is more likely a result of the games males play with
>> each other.
>> 
>and if the result of winning in these games increases the chance of acceptance
>by a female (i.e., increases the chance of passing on genes to future
>generations) then the result is the same.

Well, but it's complicated. It's likely that (higher primates again, here)
you have this male-male competition-to-mate process, and within that system
male aggressiveness is selected for (this is the first selection pressure)
because it increases the chances that a male will advance to the top
of the male-male competition hierarchy. (Think of it as a ladder.)
But FEMALES tend to not like super-aggressive males, because they're
dangerous to be around for adult females and infants alike--they
just have a hair-trigger temper. Female choice (the second selection
pressure) is for males who rise to the MIDDLE of the ladder, those
who demonstrate strength and moderate aggressiveness but not too much;
who can also be gentle and nice to be around.
So there's this process in which females continue to select from the
middle of the ladder, but male-male competition still exists as an
opposing force at a strong enough level--in order to drive 
male behavior toward the aggressive end. (why? I don't know. Because
aggressive behavior on the part of males carries risks, and so
there has to be an impetus to do it at all.)

IE, there's two processes and the two sexes have conflicting interests.

-----------
Susan Nordmark
Internet: kevin@chromo.UCSC.edu			
UUCP: ...ucbvax!ucscc!chromo.kevin		Santa Cruz, CA