From: le01167@portal.lasc.lockheed.com (Ron Nadel (x2025))
Newsgroups: sci.bio
Subject: Re: Evolution
Keywords: Sexual Selection
Date: 18 Aug 92 16:06:47 GMT
Distribution: usa
Organization: Lockheed Aeronautical Systems Co. - Rye Canyon
News-Software: VAX/VMS VNEWS 1.41

In article <1992Aug17.230830.23118@voder.nsc.com>, pad@galaxy.nsc.com (Paul Denny x8349) writes...

>I read Richard Dawkins' book The Blind Watchmaker several years ago
>and it argued that the reason for the evolution of such things as 
>Peacock tails (that do not seem to very suited to survival) was due to
>a genetic preference by females for the trait. This leads to an increased
>likelyhood of reproduction for males with longer tails with offspring that
>have longer and longer tails (males) and more and more preference for long
>tails (female).
> 
>In isolation this argument seems to work but it seems to me (not a biologist)
>that it excludes the possibility of females with a preference for tails that
>are good for surviving with - these females would mate with "sensible" males
>and their offspring would do better than the females with a "silly" preference
>and hence win the battle to survive.
> 
>Where am I going wrong?
> 
Some of the above is difficult to understand, so if I do not answer your question,
post again.

Sexual selection based on some anatomical display is a common theme throughout the
animal kingdom: the stag's antlers, the red rump and facial coloration and prominant
genitals of baboons, coloration and courting "dances" in many birds, and weird hairdos
of human teenagers.  All these "schemes" depend on appearence, not function.  The idea
is to attract a mate for the moment.  How is the intended partner supposed to "know" 
what is functionally advantageous, sensible, or silly?  Even with the amount of 
intelligence we humans think we have, our sexual selections frequently do not take any 
"sensible" factors into account - we respond strongly to our attractions and think about
it afterwards (and if you disagree with me on that point, well, I don't know what to say).

The ideas of "sensible" and "silly" need to be defined by you, I think, with regard
to tail detail.  Think about high school dating.  The rebellious young boy with
no plans for college ("silly") may hold a stronger attraction for the girls than a nerd
with a future all planned out ("sensible") - it worked that way when I was in high school
I can tell you.  Now if the name of the game is getting a mate, then concepts such as 
"silly" vs. "sensible" don't enter in.

Think of it this way:  birds' tails were selected for most likely because of the advantages
conferred on the individual by improved balance and filght aerodynamics.  Now since the thing
is sticking out there anyway, if a particular individual has a more attractive one, it will be
easier to attract a mate and pass on one's genes.  But size can be an important advantage, too.
So some groups evolved into large species (emus, ostrich, pea fowl, etc) and flight required 
too much energy or was just not possible any longer, but there's still that tail sticking out
there.

One last point.  The idea of gradual adaptations (longer and longer tails) is beginning to 
lose favor in evolutionary thinking.  You might read Stephen J. Gould's several collections
to get a feeling for some of the latest ruminations.

Ron
Newsgroups: sci.bio