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From: newman@batcomputer.tn.cornell.edu (Bill Newman)
Newsgroups: sci.bio,alt.romance,soc.men,soc.women,soc.singles
Subject: Re: Are Humans Naturally Monogamous?
Message-ID: <1990Nov23.174050.10587@batcomputer.tn.cornell.edu>
Date: 23 Nov 90 17:40:50 GMT
References: <4836@lure.latrobe.edu.au> <1990Nov22.191009.20772@watserv1.waterloo.edu> <1990Nov23.015509.14871@massey.ac.nz>
Organization: Cornell Theory Center
Lines: 39

In article <1990Nov23.015509.14871@massey.ac.nz> A.S.Chamove@massey.ac.nz (A.S. Chamove) writes:
>birds are naturally monogamous.  Non-monogamous behaviour is Very Rarely
>observed.  The males of these species can impregnate as many fertile
>females as they can have sex with, but there is no evolutionary advantage
>for them to do so (and they do not!) probably because the female needs
>the help of the male/father to rear the offspring.
>
>Normally in large animals, the female does not need the help of the male
>to rear the offspring and they are rarely monogamous (see for example
>chimpanzees, gorillas, all large monkeys (larger than a cat).  THis does
>not seem to be true of large birds (largest is the monogamous swan).
>
>-- 
>-----------------------------------------------------------------
>Arnold Chamove
>Massey University Psychology
>Palmerston North, New Zealand


It is true that non-monogamous behavior is seldom observed in birds.
However, with the advent of fast and cheap DNA "fingerprinting" techniques
for paternity testing, it has become possible for us to 
find out what the birds are doing when they think no one is watching,
and it appears that in many monogamous species, extra-monogamous sex
is not Very Rare after all.  Despite Chamove's contention, there
_is_ an evolutionary advantage for male birds in fertilizing many
females: sperm is cheap, and even if the male can only help one female
raise his offspring, a reasonable number of the other offspring may
survive.  (Especially if some other male, unequipped to do
DNA fingerprinting, helps raise them.)  There was even some speculation
about evolutionary advantages for females, but I found the logic somewhat
murkier and I don't remember how it was supposed to go.

I can't cite the reference, but I think this result made it into
several non-technical periodicals in the last two years; I believe
I saw it first in the science section of _The Economist_.

  Bill Newman
  newman@theory.tn.cornell.edu