Humans eyes have evolved to perceive light only between approximately 350-700nm, because that form of light is most common to our lifes. Other animals can perceive lights with slightly different fequencies. Can eyes theoretically evolve in a way that they can observe all light as we know it today? If not what would approximately be the maximum amount of frequencies that can be perceived?

  • $\begingroup$ Hmm, interesting question. I think there are 2 aspects. 1: As the range of frequencies increases then input of signals increases which needs a better brain. 2: Since visible spectrum has wavelength in range of nm but otherwise like radio are in metres to KMS in wavelength, I think neurons( or other special cells) could not act like antenna , so there will be limit . $\endgroup$
    – JM97
    Mar 27 '17 at 15:12
  • $\begingroup$ "...approximately 350-700nm, because that form of light is most common to our lifes." This is not correct. It just so happens that we evolved to see in this spectrum. $\endgroup$ Mar 27 '17 at 22:27
  • $\begingroup$ @anongoodnurse it is certainly no coincidence that it just happened this way. I am on my phone so I cannot link it, but there are charts that show the amount of light that reaches earth. Most of it is light between 350-700nm. It is crucial for survival to see colour and therefore we evolved into seeing it. $\endgroup$ Mar 28 '17 at 5:53

There are some limits on what light can be detected biologically based on physics and chemistry. Although there are animals that can sense more UV or more infrared than humans, they are still subject to these limitations.

How Vision Works

The way most types of vision operate is by using photons to cause a conformational change in an opsin protein by influencing a chemical bond in a sensitive molecule (a chromophore, for example retinal, which changes from 11-cis to all-trans) bound to the opsin. To sense a particular wavelength of light using this mechanism, it is necessary that the energy of the light is sufficient to cause this chemical change in the opsin-chromophore, without being enough energy to destroy the molecule entirely by breaking a bond.

Sensing low-energy (long wavelength) light

Longer wavelength light ('infrared') is also known as heat. Detecting "heat" photons is difficult because they don't have much energy. Therefore, you need a molecule that is very sensitive. It turns out that the opsin-based vision strategies use chromophores that are too stable to sense long wavelength light.

Some snakes have particular sensitivity to infrared, for example the pit viper. However, these animals do not "see" infrared using their eyes: they have another specialized organ called the pit organ. The pit organ uses receptors that are much more like the heat receptors in your skin than the photoreceptors in your eye, but the pit organ uses a pinhole camera effect to organize the incoming light onto a very sensitive heat-sensitive membrane.

Humans of course are able to sense infrared, too, but the same way: through the skin rather than the eyes, and at low resolution. However, if you stand outside in the sun and close your eyes, you can probably still "see" the direction of the sun: one side of your body will feel warmer than the other! In a way, this is like a form of low-resolution "vision" if you want to define that term very broadly. The snake's infrared sensitivity is more like this sensation than eyesight.

When you get to very long wavelengths, for example radio waves, the wavelength is too long and too low-energy to even be relevant at a molecular level: these forms of light will travel right through cells, and individual photons don't carry enough energy to influence molecules in ways that can be sensed by biology.

Sensing high-energy (short wavelength) light

Very short wavelengths of light have the opposite problem: too much energy. Ionizing radiation (from the upper ultraviolet range and shorter) has enough energy to actually free electrons and create ions. This type of radiation damages biological molecules, including DNA, so organisms have a lot of good reasons to avoid these types of radiation. Exposure to short-wavelength radiation can also cause bleaching (permanent destruction) of photosensitive molecules and potentially damaging heating of tissue surrounding pigments, in addition to direct effects on other molecules in the cells.

Insects and other organisms that can see into the UV range see mostly in the near-UV range, >300nm, not too far from our own vision range (roughly corresponding to "UVA"). However, it isn't true that humans can't see these wavelengths due to some lack of sensitivity of our photoreceptors: instead, UV light is (at least partly) blocked by the cornea and lens, presumably to protect the retina from damage!

Humans and other organisms do have some sensitivity to damaging UV wavelengths, just not through vision. Instead, humans and other organisms sense UV based on the damage done within cells, which recruits repair mechanisms and apoptosis to prevent damage from leading to cancer.


The chemical processes behind vision determine the range of potential wavelengths that can be sensed. Animals on earth are able to sample from this entire range. Mechanisms to sense wavelengths outside that range would require wholly different approaches, and maybe even a unique biochemistry. The mechanisms would have to be so different that we probably wouldn't refer to those mechanisms as "vision" (for example, even the infrared sensitivity of the pit viper isn't really though of as vision) but we would come up with a new term, such as "radio sensitivity" or "radiation sensitivity" just like we have different names for "hearing" relatively high-frequency pressure waves with the ears but we have "vibration sensitivity" for low-frequency pressure waves felt through the skin.

  • $\begingroup$ A very informative answer. However is it possible that some species could evolve a "sight" process not based on opsin? For example could a species evolve a structure capable of receiving AM radio? This article (seas.harvard.edu/news/2016/12/…) describes a very small radio that is "biocompatible". Although using "sight" to describe this wouldn't match the current meaning of the word very well. $\endgroup$
    – Χpẘ
    Mar 27 '17 at 19:17
  • $\begingroup$ @Χpẘ Yeah this is exactly what I was referring to in my Summary: I think the pit viper is a great example of a place where we might colloquially say vision, but if I search Google Scholar for "pit viper infrared" the scientific literature mostly if not exclusively refers to vision only in quotes; the other terms used are "infrared detection" or "infrared imaging"; it's a stretch to call it vision because it isn't from the eyes. $\endgroup$
    – Bryan Krause
    Mar 27 '17 at 20:00
  • $\begingroup$ @Χpẘ Also as far as biocompatibility in the article you linked, what they are referring to is that diamonds don't cause an allergic/foreign body response. No known biological mechanism can create diamonds nor substitute single carbon atoms in a diamond with nitrogen. $\endgroup$
    – Bryan Krause
    Mar 27 '17 at 20:04
  • $\begingroup$ Yes, but that doesn't mean an evolution isn't possible. Another example, IBM has built a radio out of a carbon nanotube. Looking at the future from the point of view of earliest life, I'd venture that it wasn't predictable that human sight was in the future (setting aside for a moment the question of who would've been making predictions!). The OP says "eyes theoretically evolve" which is fairly ill-defined. "Evolution" is not even limited to earth based evolution. Second "theory" could refer to a host of disciplines, such as physics, genetics, etc. Third, meaning of "eyes" would likely change. $\endgroup$
    – Χpẘ
    Mar 27 '17 at 20:30
  • $\begingroup$ @Χpẘ There is "possible" in a science fiction sense and "possible" in the sense that it could happen from known biological principles. I agree that if one leaves behind known biology in favor of non-earth based life origins and completely different biological paths that a lot is "possible" but it mostly belongs on WorldBuilding.SE, not Biology.SE. $\endgroup$
    – Bryan Krause
    Mar 27 '17 at 20:33

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