Do complex life-forms in this universe automatically develop a pair of eyes?

[steffen]

I would like to get some selective answers to the question on the end of the following text.
I am not a creationist or something like that and I know my issue is tangenting some other threads. Anyway I am not looking for a wide range of general points, but only “technical” opinions about this particular question/opinion, and for this reason I concentrate on eyes.

Looking at the forms that life has developed on this planet, it seems as if there is something involved that is not based on coincidence, but on unavoidable logic. For example: A pair of organs for visual perception.

All vertebrates, fish, mammals,birds, reptiles, amphibians, are using this tool (with few exceptions of later atrophy), as well as most of the more complex invertebrates. And they all are using a pair of such organs. It doesn’t matter if you look in the face of a bird, a lizard, a snail or an ant, you will always see this pair of visual organs.

Thinking of that like an engineer, it seems that this construction (a pair of optical /visual- sense eyes) is something that has to be used inevitable when constructing a complex animal that is meant to successfully live on land or in the water. The optical /visual perception has too many advantages; to abandon this option would not be a clever thing for the engineer. Furthermore it would not be clever to use only one eye or more then two of these organs. The best way is to take two / a pair of eyes. This way the stereoscopic vision is provided while a third or fourth eye would not bring a real advantage relative to the effort.

It looks like in general this pair of eyes had to develop this way out of logic, the same as a car would always be equipped with round wheels and not with quadratic or triangular “wheels”.

Btw, the same as with the eyes, the engineer would construct legs for the land animal and fin-like tools for those in the water, as this are the best tools for locomotion in /on the particular element (with very few exceptions existing like tail motion).

So, now the question:

Is there any logical argument possible, why / how on some other planet in this universe living things would not develop a pair of eyes when reaching a similar complexity as here on earth?

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[Dave Allen]

Well a lot of cave and tunnel dwelling animals have no need for eyes, and tend to lose them.

So a theoretical alien subterranean ecosystem would conceivably include a number of eyeless animals (or equivalents of animals).

Also there are a number of animals with more than two eyes - such as spiders, scallops, scorpions and the like. There is even a species of deep sea fish with two eyes that function as four eyes due to their unusual shape.

[steffen]

Well a lot of cave and tunnel dwelling animals have no need for eyes, and tend to lose them.

So a theoretical alien subterranean ecosystem would conceivably include a number of eyeless animals (or equivalents of animals).

OK, there are even vertebrates where the pair of eyes has become stunted, but in the big picture this seem to be few exceptions which have descented from landliving species which had used the pair of eyes. And even the regressed eyes are still existend.

So when you say "a number of eyless animals" in a theoretical alien subterranean ecosystem, do you mean something like here on earth (some specialized animals where the eyes have more or less regressed) or could there be an evolution of liveforms until the same complexity as we have it here on earth and they did not have at all developed eyes during their evolution?

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[Dave Allen]

Either or really. If a theoretical ecosystem could exist with its own energy source (such as hot vents under dirty ice - as some people like to suppose exists on some of the moons of Jupiter) then there would be no need for eyes - they would just get in the way.

[xris]

Originally Posted by Dave Allen

Either or really. If a theoretical ecosystem could exist with its own energy source (such as hot vents under dirty ice - as some people like to suppose exists on some of the moons of Jupiter) then there would be no need for eyes - they would just get in the way.

As we have never seen examples of that why should we conclude that life could evolve in that manner. Its a sensor to the environment for understanding , eyes, ears may be the basic necessity that appear to evolve then become redundant through lack of use. Light might be a necessity in creating life , so it always originates in light then deteriorates to occupy an environment where they survive on creatures that rely on light.

[pantheras]

Originally Posted by steffen

This way the stereoscopic vision is provided while a third or fourth eye would not bring a real advantage relative to the effort.

Is there any logical argument possible, why / how on some other planet in this universe living things would not develop a pair of eyes when reaching a similar complexity as here on earth?

________________________
www.basicrule.info

Why you dont have 1 eye in advance at the back of your head? I think that would be pretty usefull.
Not for us now, thats why it will not happen, but imagine world, where are primates constantly attacked by piranha-birds from back of their head. These primates still doesnt understand how to use tools, even are not wearing any clothes. And piranha birds are so intelligent to know that the most succecsfull attack is silent from the back, then go away to not get hurt.

[Dave Allen]

Originally Posted by xris

As we have never seen examples of that why should we conclude that life could evolve in that manner.

I'm not sure why anyone 'should' believe anything regarding a wholly hypothetical model. I don't think it's a question of belief so much as an aknowledgement of the likelihoods involved.

All I'm really interested in explaining here is that it's not necessary to see eyes as integral to being a 'complex' organism (whatever that is).

On our planet there are ecological niches where having eyes is a positive disadvantage - they take energy to build and can be damaged or subject to infection. Animals that live in caves or in the deep sea or tunnels often lose their eyes (whether they are relatively complex or not) or may never have evolved them in the first place.

On our planet such niches are not as common as they could be on another planet or moon, and are linked closely to niches were eyes are an advantage.

So from our vantage point eyes are smashing things because earth's ecosystem is so reliant on light in the main - and we still have lots of blind organisms here. In fact, most life on this planet does well without eyes - it's not just the animal kingdom that need be considered complex.

But because that's the way it is here it doesn't mean that's how it might be in every habitable planet or moon imaginable.

[xris]

Originally Posted by Dave Allen

I'm not sure why anyone 'should' believe anything regarding a wholly hypothetical model. I don't think it's a question of belief so much as an aknowledgement of the likelihoods involved.

All I'm really interested in explaining here is that it's not necessary to see eyes as integral to being a 'complex' organism (whatever that is).

On our planet there are ecological niches where having eyes is a positive disadvantage - they take energy to build and can be damaged or subject to infection. Animals that live in caves or in the deep sea or tunnels often lose their eyes (whether they are relatively complex or not) or may never have evolved them in the first place.

On our planet such niches are not as common as they could be on another planet or moon, and are linked closely to niches were eyes are an advantage.

So from our vantage point eyes are smashing things because earth's ecosystem is so reliant on light in the main - and we still have lots of blind organisms here. In fact, most life on this planet does well without eyes - it's not just the animal kingdom that need be considered complex.

But because that's the way it is here it doesn't mean that's how it might be in every habitable planet or moon imaginable.

Im just thinking Alan that life initially needs daylight to exist, can you give an example when it started blind. Evolution has allowed certain creatures to occupy caves but they still need to sustain themselves from creatures or vegetation that needs light. If life needs light its only natural that it uses that spectrum to communicate with its environment.

[steffen]

Dave Allen wrote:

I'm not sure why anyone 'should' believe anything regarding a wholly hypothetical model. I don't think it's a question of belief so much as an aknowledgement of the likelihoods involved.

All I'm really interested in explaining here is that it's not necessary to see eyes as integral to being a 'complex' organism (whatever that is).

On our planet there are ecological niches where having eyes is a positive disadvantage - they take energy to build and can be damaged or subject to infection. Animals that live in caves or in the deep sea or tunnels often lose their eyes (whether they are relatively complex or not) or may never have evolved them in the first place.

On our planet such niches are not as common as they could be on another planet or moon, and are linked closely to niches were eyes are an advantage.

So from our vantage point eyes are smashing things because earth's ecosystem is so reliant on light in the main - and we still have lots of blind organisms here. In fact, most life on this planet does well without eyes - it's not just the animal kingdom that need be considered complex.

But because that's the way it is here it doesn't mean that's how it might be in every habitable planet or moon imaginable.

When you say most life on this planet does well without eyes, you are absolutely right. Anyway my question was more meant about if there is something like standard- tools the most complex life forms would automatically choose during their evolutionary process.

Still, as we are talking about eyes, your other points are primary as without light there would be no eyes. For me this leads to the next more detailed questions(beyond the last question of xris): Is it thinkable / theoretically possible/realistically possible that live without light could blossom into the complex forms as on earth?
To be honest, for me this is quite unthinkable. The precondition for developing huge complexity of single species seems to be a huge variety of colleteral life-forms. The wannabe- complex life-form must have been through an unimaginable high number of different kind of experiences/challenges. I can not see the possibility of this to happen on the ground of a dark ocean, even with lots of hot vents or under earth-surface. To make my point more understandable: On our planet, life-forms have developed to live under all thinkable conditions: in water without light, in water with light, on/in land without light, on land with light. The only condition of life at the hot vents would be in water without light. (Btw: Are the hot vents existing for billion of years?)

OK, we do not have a prove for what could develop if there would be a huge area with very long lasting hot vents under ice – but at least the permanent life under our earth’ surface seems to be not really capable to develop the complexity as it can be witnessed in our light-area. (Not even on the approach.).
I absolutely understand it is very important not to define a concept without rethinking all possible options. But yet I do not see any realistic alternatives to develop life as complex as on earth without conditions similar to those on earth. And at least on this planet the "two-eye strategy" was seemingly some kind of must-be standard for the most complex life-forms.


Pantheras wrote:

Why you dont have 1 eye in advance at the back of your head? I think that would be pretty usefull.
Not for us now, thats why it will not happen, but imagine world, where are primates constantly attacked by piranha-birds from back of their head. These primates still doesnt understand how to use tools, even are not wearing any clothes. And piranha birds are so intelligent to know that the most succecsfull attack is silent from the back, then go away to not get hurt.

Under similar evolutionary circumstances as here on earth, I would assume that it is far too late for the victims to develop the third eye when the piranha birds start their hunting method. It would take very long time to closure such an extreme development and soon it is accomplished the piranha birds would change their hunting strategy and all efforts were done for nothing. It would be much more reasonable to concentrate on developing behaviour patterns to avoid the attacks. This should be possible in-between few generations.

To me the two eye concept seems to be the optimal solution in general while specific challenges can be solved with particular changing’s of not so basic characteristics / behaviour patterns.

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www.basicrule.info

[Dave Allen]

Originally Posted by xris

Im just thinking Alan that life initially needs daylight to exist, can you give an example when it started blind.

I'm not Alan.

I suggest you find something about hot vents - which are thought to be linked with the process of abiogenesis. It is certain that energy is required for life and that most of the Earth's energy is derived from the sun, but some is volcanic and life exists in underwater volcanic areas without light.

Deep sea life also does without light - but only on parasiting/scavenging other creatures.

On a certain moon of Jupiter (Titan I think - not sure) volcanic action is observed in patterns on the icy crust. It is thought that maybe the core of the moon is hot enough to maintain a layer of liquid water underneath the surface of the ice - and hot vents could provide an ecosystem there.

If life needs light its only natural that it uses that spectrum to communicate with its environment.

Light is certainly an abundanrt source of energy here - but eyes aren't always needed - plants and fungi react to light - but they don't use eyes to sense it.