Liquid water is transparent to most of the visible spectra, whereas it absorbs infrared.

Similarly, the air is almost transparent to the visible spectra too.

Could these be the reasons why our eyes evolved to "see" the visible spectra, and not IR or UV?

(Also, are there other animal species for whom water is not colourless?)

  • $\begingroup$ Human eyes are too big to see UV. Animals that can see UV have eyes of a few millimeters. Frogs and snakes are vertebrates that can see IR using an enzyme related to vitamine A, althouth mammals mostly just see color. Sea mammals only see green. The most recent photoreceptor change in primates is the acquisition of red photoreceptors to see fruit in trees, so we can't say that changes in vision have co-incided with their investment in marine and riverine environments. $\endgroup$ – aliential Jun 23 '20 at 5:29

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