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From: petrich@netcom.com (Loren Petrich)
Subject: Re: Colors (was: Dialects (Was Re: Shakespeare's Future))
Message-ID: <petrichE6t2Jv.H5M@netcom.com>
Organization: Netcom
References: <5fen7r$12i$1@unlisys.unlisys.net> <5flsht$fqc@news.fth.sbs.de> <5fmddl$sso$1@unlisys.unlisys.net> <5fn331$5u2@nntp5.u.washington.edu>
Date: Mon, 10 Mar 1997 02:21:31 GMT
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In article <5fn331$5u2@nntp5.u.washington.edu>,
Mary K. Kuhner <mkkuhner@phylo.genetics.washington.edu> wrote:

>I have been told that octopuses do not have different color receptors,
>but instead identify color by how much the light is bent going through 
>a prism..  

	I wonder if that's a misunderstanding of something -- octopuses 
have camera-like eyes, with no "prism" in sight.

>Color vision is weird stuff.  It has apparently been re-evolved many
>times in evolution.  It's not even constant among primates; some monkeys
>have a weird system in which only certain females are trichromats, while
>the rest are dichromats.  It's been speculated that dichromats may be
>better at spotting certain textures, whereas trichromats are better at
>picking out color contrasts; since monkeys live socially, perhaps they
>divide labor that way.  ("You spot the leopard, I'll look for the
>fruit.")

	An alternative possibility: they were caught in the middle of 
evolution -- either one receptor is being introduced, probably by gene 
duplication, or else one receptor is being phased out by natural 
selection (if there is not much incentive to distinguish certain colors, 
that can happen).
-- 
Loren Petrich				Happiness is a fast Macintosh
petrich@netcom.com			And a fast train
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