A question about evolution

[YemSalat]

Hi everyone!

 

I am a student of Computer Science and I have always been interested in the evolution theory.

I've got a question an answer to which I have not found so far.

I am very curios how the evolution, or should I better say some abstract living creature 'decides' which would be the next step in progression of its organism.

This is not a question about the natural selection and perhaps would be better explained with an example. For instance, if we take the evolution of an eye, it can be divided into several steps: from a simple surface of light-detecting cells into a half-cup, then into a cup, then into a sphere with just a small hole on the top. It all seems very reasonable because the progress is gradual and the benefit is obvious for the creature itself.It is the next step which I can not grasp - the step where the eye gets a lens. As highly evolved species we now can definitely say that that step is obviously beneficial. But how did the abstract organism know that it would be? How did its body start producing another kind of cells which acted as a lens? How did it know that it is the lens that would improve its vision? I would really appreciate if you could answer this for me or at least point me in the right direction.

Thanks in advance!

Edited September 13, 2012 by YemSalat

[iNow]

There is no decision. There is no knowledge. After many countless generations, mutations happen. Some are better than others, and some have a real impact on survival and offspring propagation. Those who had beneficial mutations tended to be more successful than those lacking those beneficial mutations. The mutations were selected for, and mutations continued... building each new generation on what came before. Iterative improvement through countless generations... not decisions, knowledge, nor changes in cells within one single organism.

[Ringer]

In addition to what iNow has said, remember that just because something functions in the way it does now doesn't mean it has always functioned that way. As an example think feathers (I'm going to speak of evolution as a thing because it makes it easier for communication, it is not an actual physical entity). Evolution probably wouldn't use something that would necessitate such a large jump and so many different mutations for a singular purpose like flight. So why would something need feathers without a keeled sternum, aerated bones, etc.? Well feathers also work well as an insulator, much like hair on mammals (possibly why birds and mammals are two of the only endothermic organisms). Though they were originally used as insulating material many predators with feathers could jump and attack prey from above or jump on top of large prey to kill it easier. On the flip side prey could now climb and/or jump from higher elevation and escape predators much easier than those without feathers. Since these feathered animals survived better using feathers in a way that was just a side effect those that were born to use then in more extreme ways also tended to survive and reproduce more. Keep building on that and you get birds that use feathers for what we think of them for, flight.

[YemSalat]

Thanks for your replies! Makes much more sense now.

 

So do you think that it is safe to assume that the lens of an eye could have first appeared just as a result of a completely random mutation and in fact was not a lens at all. For example it could be just a kind of a protection screen made of transparent cells which allow the light in but don't allow in any 'rubbish'? And after millions of iterations with natural selection applied this protection evolved to become a lens.

 

Do you think it sounds reasonable?

[NIF]

building on what Ringer and iNow said:

evolution happens by chance. each time there is an offspring born (well, formed in the womb), it has the chance to have its genes altered in a manner that is different from either of its parents genes. aka: it has a mutation.

Unlike in the movies, a single mutation will not turn a human into a lizard hulk (but how we wish it were so). most mutations are so small and suttle that they go completely un-noticed. such as immunity genes. that being said, there are some mutations that can cause a domino effect within the body resulting in very noticeable changes in the offspring, such as Dwarfisim.

 

the mutations themselves happen completely by chance. (not including outside factors such as radiation)

However, deciding what mutations to keep is not random. instead it is controled by the very compex system that is commonly dulled down to "survival of the fittest".

most of the time the survival of this mutation IS based of fittness. its the Biggest lion that gets to propogate his genetic code.

But sometimes it is based on other factors. an example is the redhead. once apon a time there were NO redheads, then one day a pretty young lass is born with red hair. She grows up, and has lots of babies because lots of people are attracted to this strange new hair color. and this totally over looks the fact that she will burn to a crisp on a clowdy day. so although redheads are "less fit" they have survived and propogated simply because they can.

 

Enough of that, lets get back to your specific question on how individual compex steps in the evolutionary chain happened. well there are Two answers to that question. both are very simple:

1) these evolutionary jumps were made the same way every other part of the creature was made. the progressive adition of mutations (genetic level) resulted in the final, benificial, mutation (organ level) currently seen today. By the combined effects of chance mutations and logic based selection.

2) such a thing never happened. and could never happen. evolution is a flawed theory proof by this fact and many more.

 

Although I am not giving the creationists (or even just anti-evolutionists) any justice with how I worded opinion 2, you will find that the majority of people will give you an answer that boils down to one of these two.

 

Aww. looks like you posted a reply as I was typing up one for you.

Do you think it sounds reasonable?

personally, not in the slitest. (all you did was jusmp from "how did it form a lens" to "how did it form a protective cover that could let light in but keep 'rubbish' out")

But many evolutionist will disagree with me...

[YemSalat]

So what is your explanation then?

As far as I understood the mutation does not have to be beneficial, it just has to be 'little' enough so the creature still has a chance to mate and spread its genes. I definitely have 'cut out' some of the steps between the protection screen and a lens, but that's where in my opinion the natural selection kicks in to sort out all the randomness.

[NIF]

Your explanation fits close enough into the theory of evolution. Im not sure what the leading hypothosis is, but it very well might be exactly what you said

 

So what is your explanation then?

Of the two points I gave, My view point would definately fall into the second catagory.

 

But for me to explain in detail WHY I think this over the 'scientific' explanation. we would have to start a new thread for irreducible complexity. and from there the conversation would branch out into new threads for: radiometric dating methods, evolutionary jumps and missing links, ...... and so on

 

all this can happen in good time, but as of this Monday Im off line for 2 weeks, so didn't think it prudent to start a new thread just yet ;-)

[Ophiolite]

NIF, your understanding of fitness is flawed. (More accurately, it is wrong.)

 

Fitness is not about strength, or health, which your post #5 implies it is, but about suitability for its environment. Change the environment and you change what is suitable, what is fit.

 

You argue that it is the biggest lion which gets to procreate. Do you have citations to back that up? Are you sure it isn't the one with the shaggiest mane, or the higher proportion of fast twitch muscles, or the more aggressive perosnality? You have made an assertion based on an assumption. I'd like to see the data that supports that assumption.

[jp255]

View point 2 is not an explanation. It is merely a dismissal of view point 1. So the question as to what is your explanation is, is still unanswered.

 

What is it which you specifically disagree with about the theory of evolution? you posted in the current human evolutionary pressures thread which I find a little odd. Does this mean that you think natural selection is likely? but you disagree with the evolution of complex traits which you criticise due to irreducible complexity? Do you disagree with the concept of speciation as well?

[YemSalat]

NIF, I agree that is probably not the best place (this topic) to discuss other points of view because the topic is based on the theory of evolution. However just out of curiosity I would like to ask, does your point involve a creation of some sort in any way?

 

And to be honest I am not entirely convinced by my own version of what could have happened.

Evolution is definitely not my field of expertise and I might be wrong about making such a claim, however I find it really hard to believe that the mutations are completely random.

Lets look at the situation with an eye like this: what is the chance that new transparent cells are going to grow? Pretty little. What is the chance that they are going to grow on the right spot? On the eye, not on the legs, or stomach, etc.? Does it mean then that those cells could have appeared in any other place by means of random mutation and have been wiped out by generations of natural selection?

 

I think that there should be some mechanism (entirely natural, no transcendent being involved) that 'tells' the cells of the creature how and where to grow. For example - if cells on a certain region of the creature's body are applied with pressure on a continuous basis - those cells will eventually get harder to resist it, and the creature will get a sort of a 'shield' in that area.

I suppose something similar might happen to the eye.

 

Am I completely wrong and this is all just random mutations and natural selection?

[iNow]

[YemSalat]

iNow, I've seen that video and it actually produced the original question with which I came to this forum. If the answer is right there in the video, would you mind 'sticking my nose' into it, as I might be ignorant enough not to notice it.

[iNow]

The video reinforces the point that successive generations have iterative changes via mutations, and that each generation begins on the successes that came before them in previous generations. The discussion regarding "how might the lens have evolved" begins just after 6:10 in the video. Also, my apologies but I am not sure to which question you are referring.

[swansont]

evolution happens by chance.

No, not really. There is a random component, i.e. mutations, but the outcomes after natural selection is added are not random.

[YemSalat]

So basically it is the same explanation that I gave in my second post. It is all very reasonable.

The question however is slightly different, I am not asking how did the lens appear.

 

What I am asking is (in a nutshell) - how does the eye 'know' that the protection screen from which the lens evolved should be transparent? Is the answer - random mutation preserved by natural selection?

Edited September 13, 2012 by YemSalat

[iNow]

What I am asking is (in a nutshell) - how does the eye 'know' that the protection screen from which the lens evolved should be transparent?

It doesn't. The point is that some organisms will get a transparent "protection screen" due to their genetics while other organisms will get a more cloudy or occluded one due to their genetics.

 

The ones who were unfortunate enough to be born with a cloudy layer above the lens will not be able to see as well. This will make it more difficult to find food, more difficult to avoid predators, and more difficult to find mates. Over the course of many generations, the organisms with occluded lens will start to die out... They will continually decrease in numbers. The organisms with transparent (or helpful) screens will do better at surviving and passing on their genes to offspring and soon will be all that's left across the population... The ones with mutations that made them more successful.

[YemSalat]

Yes, but how does this information about the screen gets into the genes in the first place?

I mean how does the creature 'know' that the screen needs to let the light in (be it cloudy or clear), otherwise the eye would stop functioning. Does it mean that genes have the 'knowledge' of the eye and what it is for and how it works?

 

I might be asking something completely irrelevant, I apologize. If my ignorance is obvious to you, please provide some resources that I can read on the subject.

[iNow]

Yes, but how does this information about the screen gets into the genes in the first place?

I mean how does the creature 'know' that the screen needs to let the light in (be it cloudy or clear), otherwise the eye would stop functioning. Does it mean that genes have the 'knowledge' of the eye and what it is for and how it works?

 

I might be asking something completely irrelevant, I apologize. If my ignorance is obvious to you, please provide some resources that I can read on the subject.

As a result of combinations from both parents.

 

I think most of your confusion comes from trying to think of this happening all within one person... As if one persons genes magically decide what happens. It doesn't. It happens across countless many generations. Your genes encode stuff. How that code gets expressed depends on the environment. Some of those expressions are good, some are bad. It might not be bad enough to be detrimental to existence until you get to your great great great great great great great great great grandchild, though.

 

http://evolution.berkeley.edu/evolibrary/article/evo_01

 

http://simple.wikipedia.org/wiki/Evolution

[YemSalat]

I do realize that it takes a lot of generations for the actual changes to occur.

Do you mean there was a process of trial and error with a transparent and completely non-transparent screen that took place?

[akh]

I do realize that it takes a lot of generations for the actual changes to occur.

Do you mean there was a process of trial and error with a transparent and completely non-transparent screen that took place?

 

Simplistically, yes.

 

"Trial and error" between different individuals of a population, not of the individual by itself.

[iNow]

I guess you can call it that. Mutations happen. Different traits appear. That is a fact. Some traits are beneficial. Some are detrimental. Others have no noticeable impact. The ones that are beneficial tend to do better and get selected for. The ones that are detrimental tend to do worse and are selected against. That is a form of trial and error, sure... why not... except there is no master or researcher running any experiments or tests... It just happens that way.

 

* Cross posted with akh

[YemSalat]

So there is no way an eye (or genes, or the creature - all metaphorical) can 'know' that the screen should be transparent?

 

And while I am here, I always wanted to know if this is true - they used to say that if you take a cow and pull its left eye off, then pull its cub's left eye off, then its cub's cub's eye off and so on and so on.. Eventually over a number of generations you will get a cow with only one right eye. Do you think it could be true? Does it mean that genes have an influence from external conditions?

[akh]

So there is no way an eye (or genes, or the creature - all metaphorical) can 'know' that the screen should be transparent?

 

And while I am here, I always wanted to know if this is true - they used to say that if you take a cow and pull its left eye off, then pull its cub's left eye off, then its cub's cub's eye off and so on and so on.. Eventually over a number of generations you will get a cow with only one right eye. Do you think it could be true? Does it mean that genes have an influence from external conditions?

 

Correct, there is no "knowing" involved. It just happens that a clear lens is advantageous to the individual. There could be an environment were a completely transparent lens is a disadvantage too.

 

If you pull out the eye, it does not change the genetics. The genes will still code for two eyes, that will not change. There is not influence from external conditions, or at least not in the way you posed the question.

[iNow]

So there is no way an eye (or genes, or the creature - all metaphorical) can 'know' that the screen should be transparent?

I have no idea what you're trying to ask here. This question is meaningless. It's like asking if a truck knows it might be used to haul lumber.

 

And while I am here, I always wanted to know if this is true - they used to say that if you take a cow and pull its left eye off, then pull its cub's left eye off, then its cub's cub's eye off and so on and so on.. Eventually over a number of generations you will get a cow with only one right eye. Do you think it could be true?

No, this cannot be true. You are not changing the genes of the cow by manually pulling out it's eye. The only way that future offspring may only have one right eye is if you continually breed cows that have successively smaller and smaller left eyes... Until finally multiple generations later the offspring are no longer born with left eyes. This is because you are selecting for genes that create animals with less prominent left eyes... not because you are stabbing those eyes with a fork after they are born.

 

If I cut off your right arm, and the right arm of your son, and the right arm of your grandson, and the right arm of your great grandson, do you think your great great grandson will somehow be born without a right arm? This comparison is no different from your comment about ripping out the eyes of cows.

Edited September 13, 2012 by iNow

[Ringer]

So there is no way an eye (or genes, or the creature - all metaphorical) can 'know' that the screen should be transparent?

 

No more than you know where to develop your arm.

 

And while I am here, I always wanted to know if this is true - they used to say that if you take a cow and pull its left eye off, then pull its cub's left eye off, then its cub's cub's eye off and so on and so on.. Eventually over a number of generations you will get a cow with only one right eye. Do you think it could be true? Does it mean that genes have an influence from external conditions?

 

Look up the experiments on Lamarckian inheritance and it will show that this does not happen. It was a prevailing theory before natural selection took hold, if only because there wasn't really any other. There are some ways environmental pressures and acclimation can be passed on (epigenetics), but it has more to do with genetic switches and can get pretty damn confusing.