Why can't we see infrared?

Diagoras

Unrepentant Francophile
Diagoras
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Sep 19, 2007
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Why did humans not evolve the capacity to see infrared light? Are there animals that can? It seems like it would be a great evolutionary advantage to see a predator's body heat in the dead of night. Could it just be a mutation that never occurred? Is there some sort of physical limitation on the wavelengths our eyes could perceive? Is it not as beneficial as my intuition says it should be?
 
Diagoras said:
Why did humans not evolve the capacity to see infrared light? ... It seems like it would be a great evolutionary advantage to see a predator's body heat in the dead of night. Could it just be a mutation that never occurred?
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I can't answer all your questions, but I will answer the last one. Yes. Just because a trait would be beneficial doesn't make it inevitable that it will appear.
 
Some animals can see well into the infrared and/or ultraviolet compared to humans, enough to help them see in conditions humans cannot.
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http://en.wikipedia.org/wiki/Night_vision

Rattlesnakes and other pit vipers use their eyes to see during the day. But at night they use infrared sensory organs to detect and hunt warm-blooded prey. These infrared "eyes" are cuplike structures that form crude images as infrared radiation hits a heat sensitive retina.
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http://animals.about.com/cs/zoology/a/aa061801a.htm

I presume that fact that humans are not nocturnal might have something to do with it.
 
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Have you ever seen an infrared image?

It's badly lacking in detail, infrared would only be useful at night & we evolved to be dormant at night-time.
 
There are creatures that can sense infrared, notably pit vipers. They don't actually "see" in this range, they sense body heat via the "pits" that lie between eye and nostril.

I don't know of any mammals offhand that have this ability; maybe it's just a variation that's not in the mammalian DNA set.
 
Well... it wouldn't be very useful compared to how much of a disadvantage it would be. Infrared vision in humans wouldn't be like switching night vision goggles on and off, it would be more information on top of the information we get from the visible light spectrum. Now, imagine seeing heat in the daytime near the equator, the infrared waves reflecting off of every object blurring everything into a nondescript nothing.
 
Lots of insects can detect light in the ultraviolet wavelength with their eyes. I don't know nearly enough about biology to know if it would work at the other end, and if not, why not.
 
Having a wider range of colour vision would not be particularly advantageous, since the refractive index of a material (such as the lens, cornea, and vitreous humour of our eyes) will depend on the wavelength of light passing through it. That's why blue text on a red background looks like it's vibrating- your eye cannot simultaneously focus on both the red and the blue. If your eye tried to focus on ultraviolet as well, it would be even less focussed.

I read (in either Asimov or Clarke) that the first artificial corneas were transparent to ultraviolet, thus allowing the wearers to see a far greater range of blue and purple than normal. But the newer ones are UV-opaque, so that it's easier to focus sharply on whatever it is one is looking at.
 
Madalch said:
Having a wider range of colour vision would not be particularly advantageous, since the refractive index of a material (such as the lens, cornea, and vitreous humour of our eyes) will depend on the wavelength of light passing through it. That's why blue text on a red background looks like it's vibrating- your eye cannot simultaneously focus on both the red and the blue. If your eye tried to focus on ultraviolet as well, it would be even less focussed.

I read (in either Asimov or Clarke) that the first artificial corneas were transparent to ultraviolet, thus allowing the wearers to see a far greater range of blue and purple than normal. But the newer ones are UV-opaque, so that it's easier to focus sharply on whatever it is one is looking at.
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I thought that was lens, but you could be right.

Paul

:) :) :)
 
Really interesting question and good responses. I have a good friend who is has done research for many years on eyes of all kinds of animals, in vivo and otherwise. Just fascinating stuff. I will email him and post the response.
 
Madalch said:
I could also be wrong- it's been a long time since I read that article. I'm fairly sure it wasn't the retina, at least.
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You can't replace the retina, a many a blind peoson will tell you that.

Paul

:) :) :)
 
Professor Yaffle said:
Possibly ferrets?

http://adt.waikato.ac.nz/uploads/approved/adt-uow20070126.121529/public/01front.pdf
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It's late on a Friday night so I don't know quite what to make of that. Brilliant parody, or deeply sad in a whole new way? If I were a Kiwi it would probably be easier.

"... their status as potential vectors of Bovine Tuberculosis. There was suspicion that ferrets could detect the infrared light-emitting equipment used ...
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Show me a farmer that isn't unshakably suspicious of the wildlife on his patch.
 
Diagoras said:
Why did humans not evolve the capacity to see infrared light?
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We're already pretty destructive predators. We don't need to go all the way.


Predator1Head.jpg
 
The thing you have to remember is that the mechanism for seeing is going to be pretty vulnerable to mutations (think the various forms of colour blindness). This means that there has to be a fairly strong selective pressure to keep it intact. Now in the case of basic vision and colour vision there is such a selective pressure (no sight is a major disadvantage colour-blindness less so but still enough to be selected against). There may not be enough selective pressure for UV and IR vision to be formed let alone kept.
 
Ron_Tomkins said:
We're already pretty destructive predators. We don't need to go all the way.


[qimg]http://i127.photobucket.com/albums/p144/PREDATOR_x01x/Predator1Head.jpg[/qimg]​
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You've got to feel for Gene Simmons. He isn't aging at all well.
 
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