Something I don't understand about evolution

[Balt]

The basic idea behind evolution is that beneficial mutations give an advantage to the mutated organism and that helps it to pass on its genes, correct?

What I don't understand is how mutations that are not immediately beneficial get passed on. For example, our eyes. A very complex organ that obviously could not have been the result of one or (probably) even hundreds of mutations. It must have taken many many years and many many mutations to even get limited eyesight. What was the benefit before all of those combined mutations could come to fruition?

I suppose it's possible that the development of eyesight was the incidental result of other unrelated beneficial mutations, but that seems a bit of a stretch.

For the record, I believe in evolution and I have no interest in discussing religion in this thread.

 

[Born2bwire]

I'm not sure on the answer but one way to look at it is that your eyes are just electromagnetic radiation sensors. All they are doing are responding to relative intensities of radiation within a small bandwidth. But there are other processes in your body that respond to radiation. For example, ultraviolet rays spur the tanning of your skin via the production of melanin. So at the basic level, eyes were probably a basic sensor or response to radiation that related something about the environment.

 

[compuwiz1]

Whaaaaaat? Don't you believe in God, man?

 

[jjzelinski]

I just tr to relate the emergence of vision to current organisms that have very poor eyesight, like deep ocean creatures. Their eyes are primitive but still serve a very important purpose. Now if something about their natural habitat were change in a way that demanded better visual acuity I would think the creatures that contained mutations that were associated w/ better eyesight would have an advantage over those that don't posses those mutations. I also don't assume that the organisms that have the "single" mutation of visual acuity to be limited to that particular mutation, they may have several other mutations as well that get carried on due that single advantage.

 

[ppdes]

http://en.wikipedia.org/wiki/Evolution_of_the_eye

 

[Jeff7]

Uh oh, here we go again.
This will be a bit more brief than I'd like it to be.

Yes, the eye can be a result of incremental adaptations. If you look at the final product of anything reasonably complex, it's going to look pretty amazing. The Mars Exploration Rovers, for example, are very complex machines. But the technology used was, in some cases, decades in the making. Some of it was based on Viking technology.
Or the space shuttle - it was on the drawing board since the Apollo days. Our eyes seem complex, where certain components, like the lens, are by themselves quite useless. But then, a liver or pancreas by itself would also be pretty useless.

Evolution is a very long process of incremental growth. We see the end result and attempt to judge it based on our own short lifespans, not on the much larger timescales that evolution works on.

In the natural world, you can see varying degrees of complexity in light-sensing organs. Planarians have eyespots which can only sense light and dark. Insects have more complex vision, which can identify objects, and differentiate between wavelengths. Reptiles have eyes, the covering of which is little more than a specially adapted scale.

So let's take those eyespots. I guess they're like a very rudimentary retina. A lifeform which would have some sort of protective covering over this, even just a small layering or thickening of cells, would have a better chance of preserving its vision, and thus would be able to live longer by avoiding predators more effectively. This gives it a better chance of passing on the genes for this protective covering - now you've got slightly more complexity and capability. Maybe it has a muscle in an odd place which allows it to constrict the light hitting the retina - a form of an iris. This life form would then be able to prevent its "eyes" from being overwhelmed by excessively bright light, and again, be more likely to avoid predators.
So here after many generations, you've got something that went from having exposed retinas, to something with a very primitive cornea and iris.

That's how it begins, and how it progresses. I've got a post around here somewhere that's quite lengthy, which deals with this sort of thing. I don't remember the thread it was in though. I'll try to hunt it down.



Or just check out the Wikipedia link.




Ok, here we go. Hopefully that's the right page; I have my posts/page set to something other than the default. That page, and maybe the one before it, should have my posts. They deal more with the formation of life from nonlife, but they illustrate the long processes, and myriad of iterations required for these processes to take place.

 

[RichUK]

Life on earth has been evolving for over 4 billion years.

 

[compuwiz1]

Originally posted by: RichUK
Life on earth has been evolving for over 4 billion years.

Yes, we went from having tails, climing trees and living in caves, to where people like you and I can type and argue about things in this thread.

 

[jjzelinski]

Originally posted by: RichUK
Life on earth has been evolving for over 4 billion years.

That's a heck of a lot of opportunity for incremental change considering the relatively small life span of the organisms on the planet. Even if every creature on earth had a life span of 100 years, each evolutionary branch would have 40,000,000 opportunities for mutation

 

[91TTZ]

Originally posted by: Balt
The basic idea behind evolution is that beneficial mutations give an advantage to the mutated organism and that helps it to pass on its genes, correct?

What I don't understand is how mutations that are not immediately beneficial get passed on. For example, our eyes. A very complex organ that obviously could not have been the result of one or (probably) even hundreds of mutations. It must have taken many many years and many many mutations to even get limited eyesight. What was the benefit before all of those combined mutations could come to fruition?

I suppose it's possible that the development of eyesight was the incidental result of other unrelated beneficial mutations, but that seems a bit of a stretch.

For the record, I believe in evolution and I have no interest in discussing religion in this thread.

If you ever look at pond water, some real simple organisms have a light sensor on them. They can't really see anything, but they can detect light.

I'm sure there were many variations in between them and animals with eyes, such as organisms with 2 light sensors on them that can detect which side the light is on.

 

[Jeff7]

Originally posted by: jjzelinski

Originally posted by: RichUK
Life on earth has been evolving for over 4 billion years.

That's a heck of a lot of opportunity for incremental change considering the relatively small life span of the organisms on the planet. Even if every creature on earth had a life span of 100 years, each evolutionary branch would have 40,000,000 opportunities for mutation

Even more than that, as I'd certainly hope that each creature would mate before its death was immediately imminent.

 

[Itchrelief]

If the mutation is not negative, it may not be selected out and persist in a percentage of the population. If it gets mutated again, and this time it is a positive mutation, the percentage of individuals with that mutation will probably increase.

Also, the mutation may be inherited together with beneficial mutations due to the genes' proximity to each other on chromosomes or other factors, thus the neutral mutation can also persist in this way.

Often times, physical features are not a case of nonfunctional eye precursor 1 -> nonfunctional eye precursor 2 -> nonfunctional eye precursor 3-> eye, but more a case of light detector -> improved light detector with directional resolving abilities -> eyeball -> focuseable eyeball. Or you may have something that wasn't even used remotely like an eye but mutated to become an eye. So, the precursor structure is not always nonfunctional.

Don't quote me on a biology exam or you will probably fail.

 

[jjzelinski]

Originally posted by: Jeff7

Originally posted by: jjzelinski

Originally posted by: RichUK
Life on earth has been evolving for over 4 billion years.

That's a heck of a lot of opportunity for incremental change considering the relatively small life span of the organisms on the planet. Even if every creature on earth had a life span of 100 years, each evolutionary branch would have 40,000,000 opportunities for mutation

Even more than that, as I'd certainly hope that each creature would mate before its death was immediately imminent.

Exactly. Even under the most simplified of terms the opportunity for mutation is almost innumerable.

 

[Jeff7]

Originally posted by: jjzelinski
Exactly. Even under the most simplified of terms the opportunity for mutation is almost innumerable.

And let's not forget that there's not just a single line of organisms developing at once. Millions of life forms reproducing more than once in a lifetime for billions of years - you're talking LOADS of iterations.

 

[Kadarin]

Originally posted by: Itchrelief
If the mutation is not negative, it may not be selected out and persist in a percentage of the population.

Exactly. When it occurs, a given mutation may be neutral in terms of a survival advantage given to the species, and so it would get passed on. Later, the environment may change (i.e. a new disease is introduced where only individuals with this particular mutation have immunity), and this previously neutral mutation now becomes an advantage.

 

[Itchrelief]

Originally posted by: Kadarin

Exactly. When it occurs, a given mutation may be neutral in terms of a survival advantage given to the species, and so it would get passed on. Later, the environment may change (i.e. a new disease is introduced where only individuals with this particular mutation have immunity), and this previously neutral mutation now becomes an advantage.

Now to conceive of a situation in which small wangs would become a reproductive advantage...

Dangit, guess I'm focked

 

[DangerAardvark]

Originally posted by: Itchrelief

Originally posted by: Kadarin

Exactly. When it occurs, a given mutation may be neutral in terms of a survival advantage given to the species, and so it would get passed on. Later, the environment may change (i.e. a new disease is introduced where only individuals with this particular mutation have immunity), and this previously neutral mutation now becomes an advantage.

Now to conceive of a situation in which small wangs would become a reproductive advantage...

Dangit, guess I'm focked

Small wang = being able to fit in more holes.

 

[GagHalfrunt]

Originally posted by: compuwiz1

Originally posted by: RichUK
Life on earth has been evolving for over 4 billion years.

Yes, we went from having tails, climing trees and living in caves, to where people like you and I can type and argue about things in this thread.

And someday mankind might actually evolve into an intelligent species.

 

[Eeezee]

Originally posted by: Balt
The basic idea behind evolution is that beneficial mutations give an advantage to the mutated organism and that helps it to pass on its genes, correct?

What I don't understand is how mutations that are not immediately beneficial get passed on. For example, our eyes. A very complex organ that obviously could not have been the result of one or (probably) even hundreds of mutations. It must have taken many many years and many many mutations to even get limited eyesight. What was the benefit before all of those combined mutations could come to fruition?

I suppose it's possible that the development of eyesight was the incidental result of other unrelated beneficial mutations, but that seems a bit of a stretch.

For the record, I believe in evolution and I have no interest in discussing religion in this thread.

If you more closely examine how the eye works, it's actually a very simple organ. Being able to see light is a particularly useful mechanism for survival. All you have are rods and cones. You can imagine less evolved organisms having less evolved eyes, which perhaps don't see as well or don't distinguish colors as easily.

Evolution is not Mutation->Eyeball, it's mutation->A single rod/cone-->mutation>clumps of rods/cones->many mutations later->eyeball

 

[0roo0roo]

yea in the oceans, eyespots aka just light sensitive cells on the skin would be better than nothing. shadow and light, good for hiding or detecting some motion.

i think birds have better eyes than us, their retina isn't wired from the front. same with their lungs

 

[DrPizza]

Balt, the type of question you're posing is typical of the type that creationists/intelligent design people like to use in order to persuade their audiences that evolution is a myth. Unfortunately, many in their audiences are convinced by their arguments. At the same time, science, under attack, is usually quite capable of demonstrating why the creationist assumption is incorrect. And, in the case of the evolution of the eye, they've pretty much debunked all indredulity that it needed to be a one step deal. *sigh* So the creationists have moved on to other targets. Again and again, they find processes they don't understand or cannot conceive of to provide evidence that God created things just the way they are now. This is commonly referred to as "God of the gaps." The most unfortunate aspect is that most creationists have a LOT of gaps in their knowledge. If they don't understand how anything came to be, they automatically attribute it to God.

At the same time, more and more proof of evolution (and more significantly, a lack of even one fact which would prove evolution is incorrect) does not imply any proof of the non-existence of a God. It merely provides more evidence that the Bible is not to be taken literally.