Path: utzoo!attcan!telly!lethe!torsqnt!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zds-ux!gerry
From: gerry@zds-ux.UUCP (Gerry Gleason)
Newsgroups: sci.bio
Subject: Re: Paranormal phenomena and evolution
Message-ID: <545@zds-ux.UUCP>
Date: 14 Feb 91 00:27:20 GMT
References: <1435@gtx.com> <6735@harrier.ukc.ac.uk> <104@tdatirv.UUCP> <6747@harrier.ukc.ac.uk> <106@tdatirv.UUCP>
Reply-To: gerry@zds-ux.UUCP (Gerry Gleason)
Organization: Zenith Data Systems
Lines: 28

In article <106@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes:
>In article <6747@harrier.ukc.ac.uk> sss3@ukc.ac.uk (S.S.Sturrock) writes:
>> The capacity to be
>>tall may have been around for a long time but it was not expressed, it is
>>now.  Depends on what you consider to be evolution, for instance two
>>groups of organisms might be identical genetically (at least within their
>>gene pool) but have behavior differences which mean they will never cross
>>breed, is that evolution?  If we start getting bogged down in just the
>>genetic change scenario we may be simplifying the situation too far.

>No it is not evolution, it is an environmental barrier to breeding, that
>may, with time, lead to the gradual evolution of intrinsic breeding barriers.
>Only if the behavioral differences have a genetic basis would a biologist
>claim that evolution had occurred.

This discussion prompted me to speculate about just how the evolutionary
pressures sort out on this issue.  I would think that the average height
previous to the recent change would have been in some sense optimal, and
probably hadn't changed much for a while.  Doesn't this mean that there
is the possibility that there is now an evolutionary pressure toward being
shorter?  I know it would depend on the nature of the pressure and whether
it is still operating.  Say that being 4 inches taller increases your risk
for heart attack or other conditions.  Wouldn't the actually taller population
be selected back toward the "optimum"?  Then if the behavioral conditions
are removed the population would immediately become shorter than it originally
was.

Gerry Gleason