Silly Raz question

[Razgovory]

Raz is bored and just letting his mind wander.  He speaks in third person when he does that sometimes, and some people are put off by that.  Anyway, I was wondering, would there be an evolutionary advantage to having three eyes in your face rather then two?  Two eyes give you binocular vision, would a third eye help you gauge perspective a bit better?

[CountDeMoney]

You really should let you mind wander more, like out in the street so it can get hit by a bus.

[Razgovory]

Well you're in a sour mood tonight.

[11B4V]

The Haig. I still remember to this day "I'm in control" and the dems shit themselves.

[Ideologue]

Raz is bored and just letting his mind wander.  He speaks in third person when he does that sometimes, and some people are put off by that.  Anyway, I was wondering, would there be an evolutionary advantage to having three eyes in your face rather then two?  Two eyes give you binocular vision, would a third eye help you gauge perspective a bit better?

Nope.  Eyes like chordates and cephalopod molluscs have are rather expensive, easy to damage and prone to infection.  If there were a strong evolutionary advantage to triple vision, I reckon that we would have seen it in one or the other lines of animals that developed eyes independently.  There's a huge advantage to binoncular vision, but diminishing returns kicks in pretty quickly.

Also, I don't think having three would assist in terms of depth perception since you only need two points for parallax.  But I could be wrong.

[Josquius]

Why arent there any animals (or at least not many, dont come over all internet smart guy and give me an exception) with backwards eyes as well as forwards eyes?

[Ideologue]

For the reasons stated above.  Ability to move is a given (vision wouldn't do an immobile creature much good), so you only need one set of sense organs to see all around, and having another set, while marginally useful, would impose a fitness valley during their evolution.  Also, a lot of animals have very broad fields of vision anyway.

I think there's also probably a good reason to keep the visual organs as close to the processing center as possible, due to latency, but don't quote me.

[Monoriu]

I think it is a matter of comparative utility.  Sure, a third eye maybe marginally useful.  But the resources are better spent on more useful stuff like more brain power, a better immune system, or the enlargement of certain body parts favoured by the opposite sex. 

[Syt]

Well, it might give an advantage if it was covering a different spectrum than our current eyes - say infrared.

[Brazen]

Why arent there any animals (or at least not many, dont come over all internet smart guy and give me an exception) with backwards eyes as well as forwards eyes?

Creatures like chameleons have eyes that can moved independently and are set a little away from the skull on the side of the head so they can see backwards. It suits them because they are passive hunters - they are still or move slowly and wait for prey to approach to within tongue distance. Most other predatory animals hunt on the move so need eyes that face in the direction they are moving. Should something attack predatory animals from behind, they have binaural hearing so they can determine where to turn to see the assault. Some people believe that sharks have a binocular sense of smell.

[Viking]

It's not a silly question.

You don't need a third eye because you can move your eyes. You need three data points to determine the location of anything. First eye gives you the X axis telling you how far left/right the object is. The second eye gives you the Z axis telling you how far away a thing is (by checking how cross-eyed you have to get to focus both eyes on the one object). The elevation of both eyes gives you the Y axis (by checking how far up/down you need to move both your eyes to focus on the object).

Since virtually every creature is built by genes being activated to produce a body part and then being activated to produce a mirror image of that body part (with small modifications) you will never get three eyes. The genes that make the second eye are the same genes that make the first one. This is why most animals have 2 eyes, why some fish have 4 and why spiders have 8. No odd numbers.

[Viking]

Why arent there any animals (or at least not many, dont come over all internet smart guy and give me an exception) with backwards eyes as well as forwards eyes?

There are four eyed fish. Both the fish named the four eyed fish, which actually only has two eyes, but each eyes has two sets of retinas, one for seeing in air and one for seeing in water, and normal fish which evolved two sets of eyes independently (flounder like animals with one set looking up and another looking down).

Only the flounder like fish are not lying on the side, they are actually flat.

[CountDeMoney]

The Haig. I still remember to this day "I'm in control" and the dems shit themselves.

  And I still remember telling Mom that day, "He didn't mean it like THAT!" 

[mongers]

Raz is bored and just letting his mind wander.  He speaks in third person when he does that sometimes, and some people are put off by that.  Anyway, I was wondering, would there be an evolutionary advantage to having three eyes in your face rather then two?  Two eyes give you binocular vision, would a third eye help you gauge perspective a bit better?

I don't know, but it does go against the propensity in nature for symmetry. 
So if the question was about 2 sets of eyes, I could see that as a little more likely.

[Razgovory]

It's not a silly question.

You don't need a third eye because you can move your eyes. You need three data points to determine the location of anything. First eye gives you the X axis telling you how far left/right the object is. The second eye gives you the Z axis telling you how far away a thing is (by checking how cross-eyed you have to get to focus both eyes on the one object). The elevation of both eyes gives you the Y axis (by checking how far up/down you need to move both your eyes to focus on the object).

Since virtually every creature is built by genes being activated to produce a body part and then being activated to produce a mirror image of that body part (with small modifications) you will never get three eyes. The genes that make the second eye are the same genes that make the first one. This is why most animals have 2 eyes, why some fish have 4 and why spiders have 8. No odd numbers.

This is sort of the idea I was having.  I was wondering if having three points of reference (that is eyes), would help.  Kinda like a where you measure the distance of an object in geometry or trigonometry.  I know you wouldn't actually find this in nature (at least on earth), but my question was simply if it would grant a real benefit.