Following up on my evolution comment in class. The frequencies that are absorbed the least in liquid water are the visible light band. https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File:Absorption_spectrum_of_liquid_water.png
Keenan is also right by saying the sun outputs the most light in the visible light band.
So the reason humans see visible light could be a combination of the two facts.
Also, in my searching, I learned many birds see UV light because berries often reflect UV light. http://www.pnas.org/content/100/14/8308.full
@ans Nice! Also some discussion of this coincidence here
Meanwhile, I’m going to grab a UV lamp to help me hunt for berries. Mmmm...
Humans were unable to "see" ie. distinguish the color blue until fairly recently, historically speaking. I always thought this was cool to think that our distant ancestors looked up at the sky and saw something probably completely different from how we see things.
Human vision is constantly evolving. Perhaps in the future after using LED screens for so long, our cones will evolve to precisely make a basis formed by the frequencies of RGB of our LED screens.
@kc1 Scary thought - makes me want to get outside and enjoy the sunshine! :-)
Continuing from @kc1 -- even now we don't all have the same color perception, and the systems we've talked about in class are fairly Westernized. I just saw this cool documentary about the Himba tribe in Namibia, who have like a totally different sense of color perception.
Basically, they can't differentiate between blue and green really, but shades of green that we would see as really difficult to differentiate they can tell apart in a split second!