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From: mrh@cybvax0.UUCP (Mike Huybensz)
Newsgroups: net.origins
Subject: Re: Isolation and Unique Species
Message-ID: <512@cybvax0.UUCP>
Date: Mon, 29-Apr-85 13:56:53 EDT
Article-I.D.: cybvax0.512
Posted: Mon Apr 29 13:56:53 1985
Date-Received: Wed, 1-May-85 05:46:13 EDT
References: <217@ihnet.UUCP> <995@uwmacc.UUCP>
Reply-To: mrh@cybvax0.UUCP (Mike Huybensz)
Distribution: net
Organization: Cybermation, Inc., Cambridge, MA
Lines: 16

In article <995@uwmacc.UUCP> dubois@uwmacc.UUCP (Paul DuBois) writes:
> I understand how evolution explains most of these, but I have to ask
> about one:  what is the explanation for larger animals on islands
> than on the mainland?

Predation is an important selective pressure.  If larger animals tend to
be preyed upon more successfully (because they are easier to spot, can't
burrow as well, or whatever), there will be selection to keep a species
small, despite contrary pressures (such as larger animals being able to
defend territories more effectively.)

Move the animal to an island where there are no predators for the animal,
and selection for larger size can act freely.
-- 

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