Path: utzoo!utgpu!water!watmath!clyde!burl!codas!ufcsv!gatech!mcnc!ecsvax!hes
From: hes@ecsvax.UUCP (Henry Schaffer)
Newsgroups: sci.bio
Subject: Re: Rape: and genetic selection (was Re: Rape: a genetic catastrophe?)
Summary: The population is an organizational level inbetween the family
	 and the species, and selection can occur on that level.
Message-ID: <4438@ecsvax.UUCP>
Date: 17 Jan 88 21:03:14 GMT
References: <517@gtx.com> <5129@cit-vax.Caltech.Edu> <2201@bloom-beacon.MIT.EDU> <2288@bloom-beacon.MIT.EDU>
Distribution: na
Organization: NC State Univ.
Lines: 34

In article <2288@bloom-beacon.MIT.EDU>, lazarus@athena.mit.edu 
(Michael Friedman) writes:
> ...
> 
> ... [fnord scenario]
>  If the entire population is nices then everything is fine -
> parasites kill only a few fnords and the species is fine. If the
> entire populations is nasties parasites quickly kill all the fnords
         ^^^^^^^^^^^
> and the species becomes extinct. If the population is mixed the
          ^^^^^^^
> nasties have an advantage and soon dominate the population. The nices
> become extinct and the rest of the fnords follow.
> 
> The key point here is that evolution works for the survival of the
> fittest organism, not the fittest species. In certain cases it can
                                    ^^^^^^^
> drive a species to extinction. The theory has nothing to do with
> individual cells within a larger organism.
> ... 
> 
> These are the official opinions			Mike Friedman

  The slipping back and forth between the terms  population  and 
species  is unfortunate.  Most species are composed of many more or
less isolated populations - and this gives the opportunity for selection
to go on between populations - i.e. selection on the population
level.  There are many names used in evolutionary studies for this concept,
e.g., group selection, the island model, ...  Therefore a population
can easily be eliminated, due to a scenario such as described above, 
without the species becoming extinct.


--henry schaffer  n c state univ