# Our Visual Spectrum in regard to the Sun.

**URL:** <https://boards.straightdope.com/t/our-visual-spectrum-in-regard-to-the-sun/229572>\
**Category:** Factual Questions\
**Created:** [February 16, 2004, 11:27pm UTC](https://boards.straightdope.com/t/our-visual-spectrum-in-regard-to-the-sun/229572 "2004-02-16T23:27:00Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [February 17, 2004, 8:41pm UTC](https://boards.straightdope.com/t/our-visual-spectrum-in-regard-to-the-sun/229572/21 "2004-02-17T20:41:57Z")

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One possible source of confusion, regarding “seeing” in the infrared, is that many species of snakes could loosely be said to “see” in the infrared. But they don’t use their eyes for infrared, they use heat-sensitive pits in their cheeks (hence the term “pit vipers”). I don’t think that this has anywhere near the resolution of true vision, though.

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**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\
**Post date:** [February 18, 2004, 12:43am UTC](https://boards.straightdope.com/t/our-visual-spectrum-in-regard-to-the-sun/229572/22 "2004-02-18T00:43:59Z")

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> [@](#):
>
> That works out quite well for things that live underwater, too. But it’s not enough to assert that humans see in that range because we evolved from things that lived underwater. Many insects managed to evolve a radically different set of visual apparatus, for example.

Different yes, but also evolved from aquatic ancestors, and also using the same approximate wavelengths. Yes some insects can see into the NUV, but so can some birds. And birds of course are vertebrates with that aqueous filter. What this proves of course is that the aqueous filter isn’t all that is playing the role here, although as I made quite clear, it is important.

There is no doubt that our aquatic past plays a vital role. Perhaps our receptors for specific wavelengths are more recent in origin. But the salient point is that we still ultimately rely on rhodopsin for our visual system. And that particular pigment goes all the way back to the monerans. An almost identical pigment still exists in the purple sulfur bacteria, and that is getting pretty primitive. We have an evolutionary hurdle to overcome if we want to exploit wavelengths that aren’t useful underwater. That legacy, combined with the ‘aqueous filter’ means that our vision is more constrained by what is available underwater than what the sun produces or what makes it through the gaseous atmosphere.

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