Why are blue cones rare in humans?

[Marc Verha]

http://www.newscientist.com/article.ns?id=dn664

[John Roth]

Marc Verhaegen wrote:
> http://www.newscientist.com/article.ns?id=dn664

Uh, Marc - blue cones aren't rare in humans. The most
prevalant form of color blindness is due to a loss of one of
the red cones, and that's because the gene is on the X
chromosome.

http://en.wikipedia.org/wiki/Color_vision

Color vision is interesting. It turns out that mammals in
general only have two types of cone while reptiles, insects
and birds have four. Somehow, early mammals lost two of them.
Why? No idea.

Old world monkeys picked up a third type, while new world
monkeys didn't.

Lots of animals have cones that are sensitive to different
parts of the spectrum. Pictures of how the world actually
looks to various species of bird can be fascinating: there's a
fairly famous picture of a black-eyed Susan (a kind of flower)
that shows a band around the outside that's only visible in
the ultra-violet. Trying to figure out what various birds and
other animals actually see is a current (if somewhat minor)
research topic.

There are a few people with four varieties of cone. What I
find amazing is that their brains get properly wired to handle
four color vision.

John Roth

[Paul Crowl]

"John Roth" <JohnRoth1@jhrothjr.com> wrote in message
news:1169310593.028284.184140@m58g2000cwm.googlegroups.com...

> http://en.wikipedia.org/wiki/Color_vision
>
> Color vision is interesting. It turns out that mammals in
> general only have two types of cone while reptiles, insects
> and birds have four. Somehow, early mammals lost two of
> them. Why? No idea.

The entire mammalian system initially evolved for nocturnal
activity (and sleeping by day) and the great majority of
mammals still occupy niches that are predominantly 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.)

> Old world monkeys picked up a third type,

Primates are nearly all diurnal, so can profit from colour
vision. They sleep at night, in places fairly safe from
predators.

> while new world monkeys didn't.

Nope. It's only MALE new world monkeys which lack colour
vision. Female ones have the standard primate pattern. It
is a sensible division of labour. Male monkeys can act as
watchmen or guardians at night, and see the python or
jaguar approaching. Females can find the best fruit and
leaves by day.

I find it surprising that Old World primates did not evolve
that system. Possibly it was one of those accidents of
evolution, but then vision is such a crucial faculty -- in
almost all species -- that we would expect every detail of
its workings to closely reflect the requirements of the
particular niche.

Paul.

[claudiusde]

Paul Crowley wrote:
> "John Roth" <JohnRoth1@jhrothjr.com> wrote in message news:-
> 1169310593.028284.184140@m58g2000cwm.googlegroups.com...
>
> > http://en.wikipedia.org/wiki/Color_vision
> >
> > Color vision is interesting. It turns out that mammals in
> > general only have two types of cone while reptiles,
> > insects and birds have four. Somehow, early mammals lost
> > two of them. Why? No idea.
>
> The entire mammalian system initially evolved for nocturnal
> activity (and sleeping by day)

References?

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

References?

> 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 . . ."

>
> > Old world monkeys picked up a third type,
>
> Primates are nearly all diurnal, so can profit from colour
> vision. They sleep at night, in places fairly safe from
> predators.

What's your point?

>
> > while new world monkeys didn't.
>
> Nope. It's only MALE new world monkeys which lack
> colour vision.

So what.

Female ones have
> the standard primate pattern. It is a sensible division of
> labour. Male monkeys can act as watchmen or guardians at
> night, and see the python or jaguar approaching. Females can
> find the best fruit and leaves by day.
>
> I find it surprising that Old World primates did not evolve
> that system. Possibly it was one of those accidents of
> evolution, but then vision is such a crucial faculty -- in
> almost all species -- that we would expect every detail of
> its workings to closely reflect the requirements of the
> particular niche.
>
>
> Paul.

[Deowll]

"pete" <vincent@triumfunspam.ca> wrote in message
news:ep3rb6$9ek$2@nntp.itservices.ubc.ca...
> on 20 Jan 2007 08:29:53 -0800, John Roth
> <JohnRoth1@jhrothjr.com> sez:
>
>>Marc Verhaegen wrote:
>>> http://www.newscientist.com/article.ns?id=dn664
>
>>Uh, Marc - blue cones aren't rare in humans. The most
>>prevalant form of color blindness is due to a loss of one of
>>the red cones, and that's because the gene is on the X
>>chromosome.
>
>>http://en.wikipedia.org/wiki/Color_vision
>
>>Color vision is interesting. It turns out that mammals in
>>general only have two types of cone while reptiles, insects
>>and birds have four. Somehow, early mammals lost two of
>>them. Why? No idea.
>
>>Old world monkeys picked up a third type, while new world
>>monkeys didn't.
>
>>Lots of animals have cones that are sensitive to different
>>parts of the spectrum. Pictures of how the world actually
>>looks to various species of bird can be fascinating: there's
>>a fairly famous picture of a black-eyed Susan (a kind of
>>flower) that shows a band around the outside that's only
>>visible in the ultra-violet. Trying to figure out what
>>various birds and other animals actually see is a current
>>(if somewhat minor) research topic.
>
>>There are a few people with four varieties of cone. What I
>>find amazing is that their brains get properly wired to
>>handle four color vision.
>
> Do you have a reference for that? I confess I find it rather
> hard to believe - it suggests there are people around who
> see colours the rest of us don't get to experience. They'd
> get to invent their own names for them...

Some people also have an extra gene for the color green and
yes people seem to be rather more variable in color vision
than might be expected. Why don't you just google it?

>
> --
> ==========================================================================

> vincent@triumf[munge].ca Pete Vincent
> Disclaimer: all I know I learned from reading Usenet.

[Paul Crowl]

"pete" <vincent@triumfunspam.ca> wrote in message
news:ep3rb6$9ek$2@nntp.itservices.ubc.ca...

> on 20 Jan 2007 08:29:53 -0800, John Roth
> <JohnRoth1@jhrothjr.com> sez:
>
>>There are a few people with four varieties of cone. What I
>>find amazing is that their brains get properly wired to
>>handle four color vision.
>
> Do you have a reference for that? I confess I find it rather
> hard to believe - it suggests there are people around who
> see colours the rest of us don't get to experience. They'd
> get to invent their own names for them...

It's the same difference, in principle, between 'colour-blind'
people and the rest of us. They'd be able to discriminate
between shades of (say) 'white', or of (say) indigo, which we
would find identical. So, if we were to forge banknotes using
those colours, we'd almost certainly get it wrong in their
eyes, even if we took the utmost care in our own.

Paul.

[Deowll]

"Paul Crowley" <slkwuoiutiuytciuyik@slkjlskjoioue.com> wrote
in message news:GCrth.17618$j7.342344@news.indigo.ie...
> <claudiusdenk@sbcglobal.net> wrote in message news:11695385-
> 27.808161.294930@51g2000cwl.googlegroups.com...
>
>>> 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.

True mammals didn't show up until well into the age of the
dinos. It is dubious to claim that dinos were cold-blooded.
The consensus is that many of the small meat eaters were
warm blooded.

>
>>> 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.

[Paul Crowl]

"deowll" <deowll@bellsouth.net> wrote in message
news:GtBth.1429$p%6.20@bignews7.bellsouth.net...

>> 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.
>
> True mammals didn't show up until well into the age of the
> dinos. It is dubious to claim that dinos were cold-blooded.
> The consensus is that many of the small meat eaters were
> warm blooded.

I don't think anyone doubts that the bulk of dinosaurs,
especially (a) the earlier ones and (b) the larger ones, right
up to the end, were cold-blooded.

The arguments (or the fashions) seem to me to swing back and
forth, and I have seen nothing that indicates a consensus.

The arguments against the theory would seem to be:
(i) A small warm-blooded animal would have evolved
insulation; the only likely form would seem to be
feathers. There's no evidence for them, AFAIR,
outside of birds.
(ii) Why didn't a few such taxa survive the extinction?

Paul.

[claudiusde]

On Jan 23, 9:00 am, "Paul Crowley"
<slkwuoiutiuytciu...@slkjlskjoioue.com> wrote:
> <claudiusd...@sbcglobal.net> wrote in messagenews:116953852-
> 7.808161.294930@51g2000cwl.googlegroups.com...
>
> >> The entire mammalian system initially evolved for
> >> nocturnal activity (and sleeping by day)
>
> > References?

Any book on mammals.

Title? Page #? Quote?

> Almost any website on them.

Why don't you post a link?

> Of course, no human was around at the time, and the fossil
> record does not inform us whether the animal was nocturnal
> or diurnal.

Yes, I know. This is why I was asking the question.

You should be more careful. You've already established
yourself as a person that tends to base his thinking on
evidence that exists only in your imagination.

> 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.

Bad assumptions. Bad conclusions. Bad logic.

>
> >> 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."

Are they all nocturnal?

>
> 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

Okay.

, as are the vast
> bulk of rodents.

Huh?

> 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.

So what's your point as it relates to hominid evolution?

[Rich Travs]

Marc Verhaegen wrote:
>
> http://www.newscientist.com/article.ns?id=dn664

Where in the article does it claim blue cones are rare
in humans?

From the article:

...yet whales and seals seem to have abandoned blue vision
independently.

Most mammals have two types of cells in their eyes, called
cones, that pick out blue and green light. Humans and other
primates have a third cone for red light. ...