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Comment by alok-g | Hacker News Reader

Someone once told me that the visible frequency range matches the spectrum for which water is transparent.

This person also said that this is an indicator of life evolving in water. That seems unsatisfactory though since it has been a long while on land.

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Evolution is the king of good enough. Things that work but have issues usually don't get 'revised'. For one of the funniest examples check out the recurrent laryngeal nerve which connects from your spine very close to your brain to your voice box... with a short little detour all the way down into your neck under your aortic arch back up to your voice box. [0] The main theory is it's a vestige of ancient fish anatomy and even shows up in GIRAFFES where it's over 4 meters long because it takes the same detour all the way down the neck.

[0] https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve#/med...

Wow! Thanks for sharing.

For the optic nerves in humans, a similar questiom comes -- Why does it connect to the rear side of the brain when the front is much closer! This perhaps relates animals having their eyes on the sides of the head and a relatively small brain positioned in a way that the eyes were closer to the rear side of the brain.

I'm far from an evolutionary biologist but AFAIK the majority of our brain is a late addition in the scheme of our evolution from sludge to human and vision is connected to one of the older parts and the new parts are up towards the front. Another case of the iterative nature of evolution, the frontal cortex where most emotion processing happens came about and enlarged a lot through the evolution of chimps that eventually branched off into humans.

Regardless of how long life has evolved on land, our eyes are filled with (mostly) water - so any frequencies that can't pass through water would be scattered and absorbed by the goop inside of your eyeball.

That makes sense. I should have thought of that myself. :-) Thanks!

The human visible frequencies also match the frequencies where the sun has most of its output.

Moreover, they also match the frequencies for which the atmosphere is transparent.

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