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From: mrh@cybvax0.UUCP (Mike Huybensz)
Newsgroups: net.origins
Subject: Re: Why ain't life homogenized today?
Message-ID: <752@cybvax0.UUCP>
Date: Mon, 16-Sep-85 11:36:25 EDT
Article-I.D.: cybvax0.752
Posted: Mon Sep 16 11:36:25 1985
Date-Received: Thu, 19-Sep-85 07:31:08 EDT
References: <2649@vax4.fluke.UUCP>
Reply-To: mrh@cybvax0.UUCP (Mike Huybensz)
Distribution: net
Organization: Cybermation, Inc., Cambridge, MA
Lines: 38

In article <2649@vax4.fluke.UUCP> hopeful@fluke.UUCP (Buford Wanttruth) writes:
> "WHY IS LIFE NOT HOMOGENOUS TODAY WITH
> MYRIADS OF INTERGRADING FORMS MAKING CLASSIFICATION IMPOSSIBLE?

Good question.  There's a good answer too.

Let's assume for the moment that you miscegenated with a sheep, and the
ewe gave birth to your firstborn son, the smartest offspring a sheep ever
had, and the wooliest offspring of any human ever.  This new creature grows
up into a fine example of thinghood, but has some problems.  It can't
compete well with either humans or sheep.  The rams butt him away from the
ewes, and he can't fight back because he hasn't big horns or enough brains
to use tools.  Human females laugh at him because he is too hairy and stupid.
Your offspring will likely have less success at reproduction than if you had
bred with something human.  And thus you will have fewer grandchildren than
if you had bred with something human.

This is a general phenomenon, due to specialization.  Offspring between two
different specialists are not likely to be able to compete well with either
parent species in parental habitats.  Thus, it is beneficial to specializing
organisms to stick to their own kind, and not waste their reproductive
energies on mates that will produce inferior children.

This is the driving evolutionary force producing barriers to reproduction
between species.  Assume for a moment that somehow two species have come
about, and meet in a zone where hybridization takes place.  Natural selection
will favor individuals in both species which do not miscegenate, no matter
what the reason (wrong smell, whatever.)  These characteristics will be
selected for, and spread throughout the populations, eventually forming
the barriers to reproduction that we know today.

This process is visible between quite a number of sibling species, such
as the leopard frogs, various grasshoppers, white-footed and deer mice,
voles, etc.  Individuals from where the species overlap will not miscegenate.
Individuals from where the species don't overlap will miscegenate.
-- 

Mike Huybensz		...decvax!genrad!mit-eddie!cybvax0!mrh