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From: kevin@chromo.ucsc.edu (Kevin McLoughlin)
Newsgroups: soc.men,sci.bio
Subject: Re: Sexual selection
Message-ID: <2402@saturn.ucsc.edu>
Date: 17 Mar 88 04:55:29 GMT
References: <1566@mmm.UUCP> <3138@arthur.cs.purdue.edu> <1164@microsoft.UUCP> <3455@medusa.cs.purdue.edu> <3232@zeus.TEK.COM> <13400@sri-unix.SRI.COM> <913@bingvaxu.cc.binghamton.edu> <25443@cca.CCA.COM> <914@bingvaxu.cc.binghamton.edu>
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Reply-To: kevin@chromo.UUCP (Susan Nordmark)
Organization: Physics Asylum, University of California, Santa Cruz
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In article <914@bingvaxu.cc.binghamton.edu> vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes:
>But presumably the above scenario was in effect throughout homonid
>evolution, and modern dimorphism is the "residual" effect of that.  

With the proviso that sexual selection works in two ways: 1) females
create a selection pressure for males to look like they can provide
good genes and (in hominids maybe also) help and companionship in the
hard work of raising a primate child to adulthood
2) males compete with each other for the sexual favor of the
females, which creates another selection pressure on males for 
traits that are important in this male-male competition process 
(dog-and-pony-show, really). A lot of (2) may be why males are
usually bigger than females in mammals: in some species (deer)
they fight, in other species they just try to scare and impress each
other with a mouthful of big teeth (chimps, baboons), colorful 
or hairy accouterments to the body (lions, orangutans, human males), 
aggressive show-offy behavior acting as IF they're the meanest 
SOB around (most mammalian males), etc.

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.

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