
Human Eyes Are Wired Backwards - CrocodileStreet
https://theconversation.com/look-your-eyes-are-wired-backwards-heres-why-38319
======
ggreer
Please take the article with a _huge_ grain of salt. Hundreds of millions of
years ago, vertebrate eyes originally evolved backwards. Evolution hill-
climbs, so the backwardness (and ensuing disadvantages like the blind spot)
can never be fixed. Tricks with glial cells are nature making the best of a
bad deal.

Also, the author's ignorance of biology concerns me. In one comment, he
thought that color-blind people saw in grayscale. If you know how human cone
and rod cells are set up, such an idea seems preposterous.

~~~
wyager
>Evolution hill-climbs, so the backwardness (and ensuing disadvantages like
the blind spot) can never be fixed.

Well, there's some randomness in there too. I'm sure genetic local maxima get
busted sometimes.

~~~
Retra
The problem with randomness is that it is overwhelmingly likely to produce
worse performance, not better. So much so, that it is practically impossible
to improve through random effects.

~~~
zck
Random mutations don't have to produce better performance to end up with
better results. They just need:

1\. To move you to a "bigger hill". Imagine going from no eyes to skin spots
that are slightly more delicate than regular skin, but are precursors of
light-sensing skin cells^1. Over the course of generations, eyes can evolve.

2\. To not be too deleterious. One spot of more sensitive skin won't cause the
mutation to be immediately evolved away from; it's just not that bad for the
individual.

When you say it's "practically impossible to improve through random effects",
what is "practically impossible"? How have you weighed that against the number
of individuals in a population, the number of random mutations each offspring
has, and the length of time we're talking about? The question isn't "what are
the chances a blind fish today has a baby with eyes tomorrow?" This question
both understates the number of trials evolution has to generate something, and
pins the target of evolution. Instead, we should ask "over millions of years,
what are the chances that a given population evolves something useful?"

[1] I'm not claiming this is exactly how eyes evolved.

~~~
Retra
There are two different concepts at play here. The first is the notion of
optimization by randomness and the second is evolution by natural selection.

For the first issue, there are is a simple way of seeing what I'm talking
about; If you are trying to optimize an algorithm for _given_ results, there
are three broad techniques which I will categorize for simplicity as 'stupid',
'random', and 'smart.'

For instance, if I wanted to sort a deck of cards, I could just shuffle it
until I had a sorted deck. That's 'random.' This is not the worst you can do,
and only if you do worse can random be an improvement. To do worse, you have
to actively prevent the deck from becoming sorted. (For example, by using an
algorithm that guarantees a 1-3-2 order at the start.) Randomness is not
optimization, and stupidity is optimization away from the goal. Smart is
convergence on a goal.

However, evolution is not a goal directed process. Those who exist are simply
those who lived long enough in the environments they happened find themselves.
Randomness doesn't improve any organism or any feature of any organism: it
only improves _diversity_ , which allows for more niches to be filled. I mean,
maybe this increases the availability of food or the amount of space per
organism or something, but it doesn't actually improve organisms. It improves
the environment by making it less hostile to life in the abstract.

So it has nothing to do with hill climbing or optimization per se.

~~~
zck
I think we're talking past each other. I'm not really sure what claim I made
you're responding to. I was responding to this claim you made, with the
context of "evolution":

> ...it is practically impossible to improve through random effects.

It's true that evolution is not aimed at a specific target. I made that point
in my comment.

>Randomness doesn't improve any organism or any feature of any organism: it
only improves diversity...

Here is a list of examples of beneficial mutations:
[http://www.gate.net/~rwms/EvoMutations.html](http://www.gate.net/~rwms/EvoMutations.html)
It includes things like "adaption to high and low temperatures" and "12% (3
out of 26) random mutations in a strain of bacteria improved fitness in a
particular environment."

The claim is that random mutations can occur -- at some rate, low though it
may be -- and are more likely to be kept through natural selection.

~~~
Retra
You're probably right. Maybe I was just stretching to bring up a point that
might be irrelevant.

------
dribnet
Article fails to mention: the eyes of the squid and octopus are very similar
to ours in overall structure, but are not "wired backwards". So it seems that
any explanation of why backwards is actually "vision-enhancing" is incomplete
unless it also explains why it would _not_ be enhancing for the squid. (though
perhaps a justification could exist based on different wavelengths and
lighting conditions underwater)

~~~
pygy_
The vertebrate eye evolved under water as well (in fish).

------
sorokod
Related: "Why we have blind spots - and how to see the blood vessels inside
your own eye"

[https://www.youtube.com/watch?v=L_W-
IXqoxHA](https://www.youtube.com/watch?v=L_W-IXqoxHA)

------
ozim
When I read this, I felt anxious about amount of time it takes to evolve eyes
compared to my lifespan. Feeling so small.

~~~
meric
I hope my cells don't evolve during my lifespan, because if they do it means I
have cancer.

~~~
schiffern
Don't worry, the cancer will then evolve politicians, who will hail that
evolution as an unprecedented innovation, claiming that only further
innovation and economic growth will solve cancer's problems. They'll point out
how cancer cells are special compared to other cells: how they've conquered
the natural causes of death and overcome many logistical obstacles to build a
complex high-density society with a rich history and lots of diversity.

Intrepid cells (no doubt sick of the crowding in their native tumor) will
sometimes set out to explore and colonize the unruly wild parts of the body.
It will be hard, but a few of those colonists will succeed in establishing
far-flung outposts.

Surely there will be a few environmentalist cancer cells that oppose the
"development" of the body, but the common perception among cancer cells will
likely be that those cells are just standing in the way of progress, and
anyway that the body is so vast that a single cancer cell can't do very much
to effect the outcome.

 _/ remove tongue from cheek_ ;)

------
Balgair
That the retina has the receptive cells under the 'cabling' is not novel and
is well studied. The authors here introduce the study of the glial 'supporter'
cells and their refractive indices as wave guides for light to the receptive
cells. This is actually pretty cool! Most neuroscience and physiology hasn't
considered this as an advantage before, just a quirk of evolution that the eye
is 'backwards'. Also, for other readers out there, the structure of the retina
may be a good reference
([https://en.wikipedia.org/wiki/Retina](https://en.wikipedia.org/wiki/Retina)).
To note: there are regions of the retina that differ in cone/rod
concentration. The Fovea, the center of our vision, is entirely cones, while
the outside is almost entirely rods. Also, the receptive cells have many
synapses where data is processed before it going to the optic nerve. The
retina acts similar to an FPGA in that the whole data set is compressed before
transfer.

------
ars
This has always been listed as a "proof" that God did not create people
because why would he mess up this design?

~~~
cbd1984
Which isn't how this works, philosophically speaking.

The best argument for evolution isn't a listing of how badly-designed we are,
it's a simple observation that the one simple principle of natural selection
through modified descent _suffices to explain us_. We don't _need_ any other
hypothesis. Therefore, the principle of parsimony kicks in and other, more
complicated, hypotheses are ruled out. Not absolutely, but fairly strongly, at
least until we find things that our current hypothesis cannot explain, which
hasn't happened yet.

~~~
alphapapa
The idea that, since a certain explanation appears to suffice, it must
therefore be the truth, is an obvious fallacy.

Besides that, there are many people who disagree that it suffices to explain
us.

~~~
zzalpha
Well, the GP was really just obliquely calling back to Occam's Razor.
Evolution is a very simple process that explains biological complexity,
compared to creationism, which requires a sentient creator to have invented
the universe wholesale.

Of course, Occam's razor should be treated as a guide... it's no proof.

------
walterbell
From the article, _"..we also noticed something rather curious: the colours
that best passed through the glial cells were green to red, which the eye
needs most for daytime vision. The eye usually receives too much blue – and
thus has fewer blue-sensitive cones."_

From another article on the same site, [https://theconversation.com/a-dark-
night-is-good-for-your-he...](https://theconversation.com/a-dark-night-is-
good-for-your-health-39161)

 _" Light from the Sun is strong in blue, short wavelength light ..when it
comes in the evening or during the night, it fools the body into thinking it’s
daytime. We now know that this bright blue light has the strongest effect on
lowering melatonin during the night. Your tablet, phone, computer or compact
fluorescent lamp (CFL) all emit this kind of blue light."_

~~~
bjwbell
That's why I take melatonin tablets ~20min before bed. It's one of the best
known methods to improve your sleep and overall well being.

[http://www.gwern.net/Melatonin](http://www.gwern.net/Melatonin)

------
sidcool
The human eye has always made me wonder of the sheer complexity of the human
body. It's an amazing epitome of evolutionary success...

~~~
zzalpha
Epitome? Nah. The human body is flawed in any number of ways. This article has
some interesting notable examples:

[http://www.smithsonianmag.com/science-nature/the-top-ten-
dai...](http://www.smithsonianmag.com/science-nature/the-top-ten-daily-
consequences-of-having-evolved-72743121/)

Humans are optimized in some very specific ways, but at the expense of some
serious downsides.

As a related aside, I think its this misunderstanding that confuses people
into preferring creationism. If one holds the anthropocentric view that humans
are the peak of biological evolution (itself a meaningless concept...
Evolution is about fitness, it's not directional), believing in creationism is
a lot more understandable.

~~~
vinceguidry
From the article:

> One of the reasons it is so difficult to stop hiccupping is that the entire
> process is controlled by a part of our brain that evolved long before
> consciousness, and so try as you might, you cannot think hiccups away.

I can. Reliably. I concentrate in the general direction of my diaphragm, and
often times I can stop the third hiccup before it happens. I have to wait
until the second hiccup before I know I'll have to use the technique. The only
time I can't do it is when I've been drinking, which is, coincidentally, when
I get them the most. I can't concentrate the way I need to, it's like that
part of my brain is shut off.

~~~
maxerickson
For fun, maybe try to "count" with the stops. 3rd hiccup, 4th hiccup, 5th
hiccup.

That would be a much more compelling anecdote about control.

~~~
vinceguidry
When I'm drunk enough to not be able to stop my hiccups, they usually go away
naturally without me even noticing them as I sober up. I eventually give up
trying to control it after I notice it's futile, and the awareness that I'm
even having them goes away. The hiccups themselves barely register and are
quickly forgotten.

A couple of times I've gotten home realization dawns that I'm still hiccuping.
Two, three hiccups later, they're gone. There's something about being alone in
my room that makes me more capable of doing the technique than when I'm at the
bar.

------
mirimir
Very cool! I've often wondered about that.

