
The evolution of eyes - sajid
https://www.nationalgeographic.com/magazine/2016/02/evolution-of-eyes/
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mamoswined
I'm surprised they didn't mention jumping spiders (Salticidae), which are
notable because they are inverts, have the ability to see an unusual number of
colors, and unlike the mantis shrimp can be _trained_ on them. Also another
advantage is they can be rewarded with sugar water. Evolutionarily, their
eyesight is a marvel. No other spiders really have anything approaching it.

[https://news.nationalgeographic.com/2015/05/150518-jumping-s...](https://news.nationalgeographic.com/2015/05/150518-jumping-
spider-color-vision-mating-animals-science/)

I have a couple as pets ([https://medium.com/@melissamcewen/how-i-ended-up-
with-pet-ju...](https://medium.com/@melissamcewen/how-i-ended-up-with-pet-
jumping-spiders-187d70a3e296)) and sometimes have managed to get them
interested in videos of other bugs but I'd like to develop something geared
just towards them. There are a couple of things like this used in the lab, but
nothing open sourced that I know of.

~~~
rectangletangle
_unlike the mantis shrimp can be trained on them_

Interesting, IIRC mantis shrimp are considered one of the more intelligent
forms of arthropod. Perhaps it's just not the correct sensory system to
communicate with them through. Evolution is certainly capable of honing an
organ system's acuity independently from the organism's brain/CNS.

On a related note, it's amazing how many times eyes have seemed to
independently evolve. And once they do occur in a species, it takes a lot of
evolutionary pressure to get rid of them. Troglobites or stygobites generally
still have atrophied vestigial eyes, despite being adapted to a purely
subterranean environment. It would seem with the relatively stable ecosystem a
cave would provide, stabilizing selection over a long while would select for
no eyes. However vestigial eyes are still common, which I suspect implies the
metabolic cost to fitness ratio of eyes must be strongly in favor of having
eyes, even if barely functional.

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mamoswined
Yeah I wouldn't be surprised if they were a bit more intelligent than jumping
spiders through it's hard to judge relative intelligence in animals like
these. For mantis shrimp color training probably doesn't resemble anything
they encounter in the wild. For jumping spiders, they use colors for sexual
selection in most species and also color is a major signal for "poisonous" in
their prey — i'm not sure that's the case with mantis shrimp.

~~~
rectangletangle
You are right, it is difficult to compare intelligence here, because it's
predicated on some objective measure of intelligence. It's also difficult
because the ways intelligence can manifest can look very different depending
on the instance. Perhaps a more general term like "sophisticated" would be
appropriate, seeing as they've adapted highly complex responses to a very
dynamic and complex environment.

Biology as a field is riddled with these definition based problems, because
the phenomena it's used to describe are just so intricate. Another similar
problem is the "species problem," where we find countless attempts at an
objective and universal definition for differentiating species, but little
consensus.

In the case of mantis shrimp it's probably the stimulus being too foreign to
the organism for it to have a meaningful response, like you said. So it's
probably just ignoring the stimulus until it to goes away.

It may also be the organism's adaptation to an environment with many diverse
predators (like a shallow water reef would have). So any unusual stimulus is
automatically interpreted as threatening. If they have a tendency to freeze
when exposed to acute stress, it may just be their manifestation of the fight-
or-flight response. This could probably be measured by comparing nervous
system arousal between threatening and foreign stimulus.

~~~
mamoswined
This is one of my fav papers: How (not) to train your spider: successful and
unsuccessful methods for studying learning
[http://www.tandfonline.com/doi/abs/10.1080/03014223.2015.112...](http://www.tandfonline.com/doi/abs/10.1080/03014223.2015.1127263?journalCode=tnzz20)

Because it has all the failed methods for training them that never got
published. Some of them are unintentionally hilarious too. > In our
laboratory, we also used sprays of water as an aversive stimulus—spiders that
moved into one side of an arena received a spray of water. In pilot trials,
there was no evidence of learning: spiders ran wildly when sprayed and then
stopped to groom themselves. If accidentally sprayed too heavily, they became
trapped by the water droplet.

I think more papers like this should exist.

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vvanders
One of my favorite eye related articles talks about The Hobbit and why 48FPS
looks so bad to some people: [http://accidentalscientist.com/2014/12/why-
movies-look-weird...](http://accidentalscientist.com/2014/12/why-movies-look-
weird-at-48fps-and-games-are-better-at-60fps-and-the-uncanny-valley.html)

It turns out our eyes vibrate a bit(~80HZ) to get a higher information density
by injecting noise, increasing sampling above the discrete quantization[1].
His theory is that 48FPS ends up being really close to the nyquist limit and
wreaks all sorts of havok on how we process the film.

[1]
[https://electronics.stackexchange.com/questions/69748/using-...](https://electronics.stackexchange.com/questions/69748/using-
noise-to-increase-effective-resolution-of-adc)

~~~
euyyn
Oh my god that uncanny valley graph from Wired :D

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orf
I've always wondered what having eyes in the back (or side) of your head would
be _like_. Two eyes in the front is kind of like a cockpit, you see forward
and have to turn. Would having an eye in the back of your head be... Behind
you? Would you be aware of the blind spots around the side of your head?

We are very ingrained in having forward facing sight, I think the mere idea of
having eyes in a different position is pretty incomprehensible to us

~~~
conistonwater
Lots of birds and fish have eyes on the side
([https://en.wikipedia.org/wiki/Bird_vision#Extraocular_anatom...](https://en.wikipedia.org/wiki/Bird_vision#Extraocular_anatomy)),
and they seem to be doing okay. Presumably you lose depth perception, so you
can't hunt things, only run away.

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bharath28
Richard Dawkins has talked about this fascinating subject several times in
interviews (and in his books). It is a beautiful demonstration of how
complexity and seemingly magical things can emerge from small changes over
large periods of time. e.g:
[https://www.youtube.com/watch?v=fzERmg4PU3c](https://www.youtube.com/watch?v=fzERmg4PU3c)

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ravenstine
Although this is rather dated, if you liked that article you may also like
Richard Dawkins' talk on the evolution of the eye:
[https://www.youtube.com/watch?v=2X1iwLqM2t0](https://www.youtube.com/watch?v=2X1iwLqM2t0)

It's pretty cool seeing a much younger energetic Richard Dawkins talk about
how the eye evolved multiple times.

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m3kw9
Maybe human eyes will evolve to better read smaller characters over a bigger
area like the ever expanding phone screens

