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Sun 7 Feb, 2010 05:25 am
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?
@steffen phil,
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.
@Dave Allen,
Quote:
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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@steffen phil,
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.
@Dave Allen,
Dave Allen;125715 wrote: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.
@steffen phil,
steffen;125699 wrote:
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.
@xris,
xris;125722 wrote: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.
@Dave Allen,
Dave Allen;125771 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.
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.
@xris,
xris;125785 wrote: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.
Quote: 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.
@Dave Allen,
Sorry Dave , I appreciate basic life might not need eyes to survive , thats obvious but we are, I thought, considering the evolution of life. When life evolves and needs more than simple nutrients to evolve.
@steffen phil,
steffen;125799 wrote: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.
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It does look like eyes have developed a number of times independantly of each other in the evolutionary tree. So I think it's certainly likely that such organs would result from similar processes on another planet.
I'm just not sure its a given.
[quote]Is it thinkable / theoretically possible/realistically possible that live without light could blossom into the complex forms as on earth? [/quote]
What do you mean by 'complex'?
Something like a mole or a fish - I can't see why not.
It's very hard for me to think an intelligent tool-using creature like a bonobo could evolve without sight.
But that's only because tool-use is so sight based in my experience.
Quote: (Btw: Are the hot vents existing for billion of years?)
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Not individually, though at the edge of two continental plates moving apart there would be a persistant area of vents for millions, if not billions of years.
Most species that currently subsist off of hot vents are able to relocate to a fresh vent (or spread their offspring in that direction) when the one they live on starts to give up the ghost.
[quote]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. [/quote]
Well - you haven't defined what you mean by complex.
Even so - we'd not expect to see complex life on earth without some notion of eyes because eyes have been present in important transitions - the early tetrapods had them - so everything that came later had eyes as part of their genetic legacy.
But if the story had been different - who knows?
An alternative that might intrigue you are the sense organs of the Tuatara (as a land dwelling reptile I'd call it fairly complex, and it has a sort of third eye which might have an interesting evolutionary heritage ahead of it):
Tuatara - Wikipedia, the free encyclopedia
Or the heat sensitive pits in snakes, or the sonic imaging of bats and dolphins.
The question is - is it hard to imagine alternatives because the alternatives are impossible - or is it because we humans are so reliant on our vision (we are very visual creatures) that we simply can't imagine having a sense that could compesate for loss of sight?
@Dave Allen,
I do suppose it depends on what you call eyes. If its for detecting your surroundings any detecting instrument could be called eyes. Eyes appear to be the most successful. They can see further than any other instrument, judge distances and can be placed to suit the animals purpose. I cant see anything being superior than eyes, so it would be of evolutionary advantage.
@xris,
xris;125833 wrote:I do suppose it depends on what you call eyes.
I think, technically speaking, it has to be a light-detecting organ to be considered an eye.
I might be wrong - but whilst an insect's compound eye might be as different from your eye as a bat's echo-location equipment - the eyes are still eyes and the echo-location is something different.
Quote: If its for detecting your surroundings any detecting instrument could be called eyes. Eyes appear to be the most successful. They can see further than any other instrument, judge distances and can be placed to suit the animals purpose. I cant see anything being superior than eyes, so it would be of evolutionary advantage.
Within our niche - yes. Whatabout life developing on a theoretical planet shrouded in fog, or tidally locked so that one side was in darkness, or some other scenario where light was low and sight limited?
It might be no advantage to have eyes in such a place.
@Dave Allen,
Dave Allen;125836 wrote:I think, technically speaking, it has to be a light-detecting organ to be considered an eye.
I might be wrong - but whilst an insect's compound eye might be as different from your eye as a bat's echo-location equipment - the eyes are still eyes and the echo-location is something different.
Within our niche - yes. Whatabout life developing on a theoretical planet shrouded in fog, or tidally locked so that one side was in darkness, or some other scenario where light was low and sight limited?
It might be no advantage to have eyes in such a place.
echo might be better in certain circumstance but given the right conditions eyes must be the most efficient.
@Dave Allen,
Dave Allen;125771 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.
Excellent points. A species doesn't waste resources on a device that isn't worth it. There's a sublime economy to organisms. Life can be conceived as organized and self-organized energy and light is only one source of energy
and information.
It's conceivable that in some utterly dark but electrically charged environment, an organism could "run on" the movement of electrons. Life on heat-vents is amazing enough in itself, and encourages an open mind, I think, on issues like this.
@steffen phil,
Have a look for the book
Life's Solution: Inevitable Humans in a Lonely Universe, by Simon Conway Morris. Conway Morris is not a creationist, although he is a Christian (however some seem unable to make that distinction.) But more to the point, he is a professor of Paleontology at Cambridge and a world-renowned expert on the Burgess Shales. Brief review is as follows:
Quote:He uses convergence as his foundation, defining it as "the recurrent tendency of biological organization to arrive at the same 'solution' to a particular 'need'" and offering a multitude of examples, including eusociality, olfaction, and the generation of electrical fields. In outlining the direction and inevitability he believes is inherent in evolution, Conway Morris stacks up compelling evidence in the form of a revealed "protein hyperspace" that limits the possibilities of amino acid combination to a few, often repeated (pre-ordained?) forms. While he skirts a focus on the relentless environmental pressures that result in adaptation, Conway Morris also derides the notion that the gene rules evolution. He accuses his opponents (primarily Stephen Jay Gould and Richard Dawkins) "genetic fundamentalism" who use "sleights of hand, special pleading, and sanctimoniousness... trying to smuggle back the moral principle through the agency of the gene." Dense with examples and complex biological proofs, Life's Solution is not an easy explanation of convergence for general readers. Still, it is a clear and exciting elucidation of the theory that evolution might have predictable outcomes, even for those who find Conway Morris' metaphysical arguments unconvincing.
I have bought this book out of interest but the biological proofs are indeed complex and I have retreated to more cultural history and general philosophy. But it is a serious argument from a well-qualified writer on the exact topic you have brought up.
@steffen phil,
Sometimes I think of mammalian life as "water-on-fire" or burning water. We are wet sacks of slow-burn, aren't we? Eat food, sh*t the ashes. And we are smarter than the average blaze, as we move intelligently (efficiently) toward our fuel.
@steffen phil,
you been snorting blake's ashes again?
@jeeprs,
jeeprs;125922 wrote:you been snorting blake's ashes again?
Does it sound that strange? Is not metabolism a fire? We breath to get oxygen to our fuel. We excrete to get the ash out of the way of our next meal.
The fire metaphor is good, I think, because it's a dynamic metaphor. If we burn too hot, the fire melts its memory/control-device (the brain). If the fire burns too cold, it goes out.
Fire releases the energy pent in molecules. Sounds like digestion. It "spreads." Sounds like reproduction.
I was going to call it "just a metaphor," but it's closer to the "truth" than most metaphors.
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