The human eye has evolved to become sensitive only to visible part of the electromagnetic spectrum. Why? Why is infrared vision disfavoured for us by evolution but not for some other animals? I am not an expert of biology but curious.

  • $\begingroup$ First hit on google. There are some complete answers there and elsewhere! $\endgroup$
    – S Pr
    May 10, 2019 at 14:25
  • $\begingroup$ I searched google. I found this answer on quora quora.com/… It says that "because that’s what we evolved to use to find food and mates, and to identify threats to survival. ". But it doesn't make sense to me. Humans also have survival threats at nights. $\endgroup$ May 10, 2019 at 14:31
  • $\begingroup$ 99% of all the photons in the universe are from the cosmic background radiation, echoes from the big bang, the rest is infrared, save for 0.001% of the photons which are visible. We can sense IR with our skin, UV requires small eyeballs, and yes i want IR vision. $\endgroup$ May 12, 2019 at 5:19

1 Answer 1


Actually, it's got nothing to do with evolution or even human biology.


What’s in a name? That which we call a rose, By any other name would still smell as sweet. William Shakespeare.

First, try to define visible yourself. Next look at the definition of it in various respected dictionaries; in our context it means

that can be seen

Consider the case of Goffin's cuckatoo, they can see as far up to as ultra-violet spectrum. They don't speak English (or Portuguese for that matter) but for them visible would mean "what they can see".

So, coming back to your question, even if we had capability to see, say, infrared spectrum, visible would have meant: VIBGYOR + infra. And then we'd have complained about not being able to see bacteria with naked eye :P

  • 1
    $\begingroup$ I think it's pretty clear the OP is not asking for the pedantic answer, nor does the pedantic answer have anything to do with biology. $\endgroup$
    – Bryan Krause
    May 10, 2019 at 16:52
  • $\begingroup$ @BryanKaruse sorry for that. But OP didn't show effort on their part and the question text lacked necessary specifications. Also, OP admits lack of expertise, a bio-physics answer would be pedantic for OP. $\endgroup$
    – RinkyPinku
    May 10, 2019 at 17:00
  • $\begingroup$ shall I find a cockatoo speaking portuguese on YT? :D $\endgroup$ May 12, 2019 at 5:20

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