Re: Why are blue cones rare in humans?

<claudiusdenk@xxxxxxxxxxxxx> wrote in message
news:1169538527.808161.294930@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

The entire mammalian system initially evolved
for nocturnal activity (and sleeping by day)

References?

Any book on mammals. Almost any website
on them. Of course, no human was around at
the time, and the fossil record does not inform
us whether the animal was nocturnal or diurnal.
But since all living mammals are warm-blooded
and since mammals evolved into a world
dominated by cold-blooded (and therefore
diurnal) reptiles, the conclusion that they
evolved into nocturnal niches is inescapable.

and the great majority of mammals still occupy
niches that are predominantly nocturnal.

References?

http://en.wikipedia.org/wiki/Rodent
"Rodentia . . . over 40 percent of mammalian species belonging
to the order."

http://www.angelfire.com/pa/bats/batbody.html
"Of the nearly 900 species of living BATS, they comprise 30% of all living
mammal species known"

Nearly all bats are nocturnal, as are the vast
bulk of rodents. That's 70% of mammals for
a start. Examine the remaining orders and,
apart from primates, you will find that the
great majority are primarily nocturnal.

Their
primary need is to able to find their way around
at night, and spot predators (or prey). Colour
vision is largely irrelevant in dim lighting, so
they don't have it.

That's why most terrestrial mammals, especially
carnivores, can see better than humans at
night. (Jim McGinn please note.)

What's the that in your "That's . . ."

The collocation of facts stated in the previous
paragraph.


Paul.


.

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