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Monkey see (colors), Monkey do (was RE: Marsupials see colors)
> From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of
> T. Michael Keesey
> On 3/27/06, Guy Leahy <firstname.lastname@example.org> wrote:
> > This is interesting... This would appear to knock more
> > holed in the hypothesis that black and white vision is
> > predominant in mammals because they started out as
> > nocturnal animals in order to avoid competition with
> > dinosaurs (who were hypothesized to be primarily
> > diurnal, although that might not be true, either.)
> It looks like only one marsupial species has been investigated:
> _Sminthopsis crassicaudata_, the Fat-Tailed Dunnart. Isn't it also
> possible that trichromacy is a synapomorphy of some metatherian
> subclade that includes _S. crassicaudata_?
Apparently in honey possums and wallabies, too.
> After all, trichromacy
> evolved at least twice among placentals (platyrrhine and catarrhine
If only it were that simple...
The following is discussed in "The Howler Monkey's Tale" by Dawkins & Wong in
Dawkins' _The Ancestor's Tale_ (and refs therein).
New World monkeys have odd sex-linked trichromatism (distinct from human
sex-linked color-blindness: male color-blind humans are genetically
trichromatic, apparently, but one of their opsins doesn't operate correctly).
Blue opsin genes are present in both sexes, and are not sex-linked. Red and
green opsins are on the X chromosome.
So a male will have blue and either red or green. And females have blue and one
of the following: only red, only green, or red and green.
And that's merely for the presence of the gene: not whether it's activated or
not! But assuming both copies are active, any population of New World monkeys
In howlers, a gene duplication and/or translocation has resulted with both R &
G on X, making them trichromats.
Thomas R. Holtz, Jr.
Senior Lecturer, Vertebrate Paleontology
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
Building 237, Room 1117
College Park, MD 20742
Phone: 301-405-4084 Email: email@example.com
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796