Re: A full spectrum of opinions

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

 From: rowe@lepomis.psych.upenn.edu (Mickey Rowe)
 > All of the opsin genes, for the rod as well as the cones appear to
 > have evolved from the same primordial gene. 

Not only that, but many humans have multiple copies of these genes,
often with slight allele differences between the copies.

 >...  The
 > genes for the cone pigments started diverging from each other to yield
 > the one coding for our short wave sensitive opsin and the gene that
 > would lead to those coding for our long and mid wave sensitive opsins
 > about 200-300 MY ago.

Or about the time that the Synapsids were diversifying in the Permian
and Early Triassic.

 >  Our mid and short wave opsins diverged from
 > each other around 30 MY ago.  (These numbers are all from Jacobs.)

Or in the Neogene - the second half of the Cenozoic.  This is
very recent, and pretty much confirms the dichromatic nature
of early mammals.

[This is even after the origin of the anthropoid primates -
what we call monkeys and apes].

The fact that birds have four color pigments, and that these
are the same four color pigments as found in lizards (that is
they diverged near the base of the sauropsid radiation, or before).,
strongly indicates that not only did dinosaurs have color vision,
but that they had four color pigments, like modern birds.

 >... Dinosaurs probably not only had more visual pigments than us,
 > their pigments were probably very different from ours and screened by
 > oil droplets like those in bird, lizard and turtle retinas.  It's also
 > reasonable to believe that they were sensitive to polarization.  Which
 > reminds me... I should be writing my thesis instead of this message

This does seem likely - any feature found in *homologous* form
in both lizards and birds is almost certain to have been present
in dinosaurs.


This is why I suspect that to our eyes the coloration of dinosaurs,
at least when in full seasonal display, would have been similar
to what we see in birds and the more colorful lizards.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.