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From: colby@bu-bio.bu.edu (Chris Colby)
Newsgroups: sci.bio
Subject: Re: Paranormal phenomena and evolution
Message-ID: <75075@bu.edu.bu.edu>
Date: 19 Feb 91 07:41:35 GMT
References: <1435@gtx.com> <6735@harrier.ukc.ac.uk> <104@tdatirv.UUCP> <6747@harrier.ukc.ac.uk> <106@tdatirv.UUCP> <545@zds-ux.UUCP>
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Reply-To: colby@bu-bio.UUCP (Chris Colby)
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In article <545@zds-ux.UUCP> gerry@zds-ux.UUCP (Gerry Gleason) writes:

>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.

	Why would you think that? Specifically, why would you think 
that height, as such, is trait? Could it not just be, as mammals, we
need a certain amount of "equipment" (organs, muscles etc.) to
survive and when you add it all up we end up at some height. Also
why, if height is a trait, should it be optimized? What mechanism(s)
would accomplish this optimization? 

> 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.

	What is an evolutionary pressure?

  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.

	I don't really think height is a trait. To me it's kind of
like your chin, it's not something of any use just a byproduct of
how we are put togethor. (Granted severe deviations from the norm
could be deleterious not only to mere survival, but also to the
ability to find a mate and reproduce.) Organisms cannot be "atom-
ized" into traits, each of which is optimized. Each and every trait
effects each and every other trait in such a way that none can
really be optimized (IMHO). It is the organism as a unit that must
"work", not each trait in a vacuum.

	Just a few thoughts to ponder, comment on or start a flame
war over 8-)

>Gerry Gleason

Chris Colby
email: colby@bu-bio.bu.edu