Newsgroups: sci.bio
Path: utzoo!rising
From: rising@utzoo.uucp (Jim Rising)
Subject: population regulation
Message-ID: <1989Mar15.165132.21617@utzoo.uucp>
Organization: U of Toronto Zoology
Date: Wed, 15 Mar 89 16:51:32 GMT

Carole, methinks that you are confusing proximate effects with ultimate
causes.  The specific examples that you cite presumably have evolved 
because they maximize the lifetime reproductive success of the individual
males and/or females involved (there may be conflicts in their individual
maxmizing strategies, as in the bears that you mention), as Gordon suggests.
Individual maximizing behaviours may on occasion have the effect of 
reducing the overall productivity of the group, but this is incidental
(except under very special conditions) to the evolution of the behaviour.

It's sort of like saying that people have sex because it is fun.  Well,
proximally, that is the reason, but ultimately they were selected to
have sex because it enhanced their individual fitness.
Comparably, a male bear may attempt to kill young because they compete
with him and perhaps his young for resources, and there is low
probability that they are his own offspring.  If this is the case,
it increases his lifetime reproductive success, and it is irrelevant
(to him) whether or not this is good for bears in general.  In this case
it is highly likely that it decreases the female's LRS--but that, too, 
is evolutionarily irrelevant, except that it would select for females
who were able to protect their young.
--Jim Rising
-- 
Name:     Jim Rising
Mail:     Dept. Zoology, Univ. Toronto, Toronto, Ontario, Canada    M5S 1A1
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