Doubting Didymus

Luvluv. I've noticed that every time we give you a simplified hypothetical, you ask for more specific information. When we increase the detail of the information we are giving you, such as peez's last post, it ends up being too complex for a layman to fully grasp. I certainly don't think of you as the enemy, and in fact I have seen few people on the anti-evolution bus as open to ideas as you seem to be. I'd like to try filling you in on the neccesary basics of cell biology and genetics that you will probably need if you are going to be satisfied with our explainations. If you don't mind, could you give me an idea of how much you know about basic cell biology by telling me if you know about any of the following:

The structure and properties of phospholipid cell membranes.
The position and function of proteins in cell membanes.
What a protein is made of.
How DNA templates code for proteins.
What basic genetic mutations are, and what they do to proteins.

It would be my pleasure to give you any basic information you need about these ideas, because these are the things I think you need to know about in order to understand my hypothetical 'signal protein becomes receptive to light' scenario, that peez also took up.

MrDarwin

And I think that's the way evolution operates, in virtually all cases. "New information" (whatever that means) arises by using "old information" in new ways but the information serves dual purposes during the interim, as with the evolution of wings from forelimbs in early birds: the limbs could be used for walking and grasping [i]and climbing and flying, but over time, flying was such an enormous benefit that the wing became more specialized to optimize that function, at the expense of the others--a morphological transition that is documented in the fossil record. Likewise, we can trace the origin of tetrapod limbs from the fins of fish; but as far as we can tell, these limbs were not used for walking on land in the earliest tetrapods, but were really just another kind of fin, even though they had the framework of the terrestrial tetrapod limb already in place.

Now, we can take that back all the way to the earliest vertebrate or chordate, and say, where did that precursor to the wing-leg-fin come from in the first place? And truthfully, that's something we don't know (yet)--but we have a pretty good record of what happened after that point.

Regarding luvluv's questions about photocells, my background in chemistry and physiology is shaky at best (my specialty is morphology) and 20 years behind me, so I can't really answer your questions to your satisfaction. But I'd like to point out that virtually all animals are sensitive to light to some degree, even unicellular protists--in a sense, the entire organism acts as an "eye". So I suspect that the ability to detect light probably predated the evolution of multicellular animals. And secondly, I'm willing to bet that the pigments or other chemicals involved in photoreception, or compounds extremely similar to them, serve other functions in the cell--because things do not appear from nowhere, without precursors of any kind.

MrDarwin

luvluv, I didn't mean that as an insult. I meant to underscore that biologists are not abandoning evolution in droves, precisely because the work we do every day convinces us of its truth. This is certainly the case for me, and is one of the reasons why I am critical when non-biologists (or even people with biology degrees but who aren't actively involved in biological research) claim that evolutionary theory is fatally flawed. If it were, don't you think that the people who study and use it every day would figure that out for ourselves? I have yet to meet a single biologist who delved into some problem only to conclude, "evolution isn't true."

Albion

It certainly does, doesn't it? I'm also wondering how relevant this "information" stuff is to biology in the real world if information is defined in terms of types of complexity and complexity is defined in terms of information. It might give ID creationists lots of stuff to argue round in circles about, but philosophy isn't biology.

There's documented evidence of a bacterium that was grown for generations on a substrate containing nylon, and after a number of generations, it (as in "a descendant of one of the original individuals") developed the ability to digest nylon. This came about by a gene duplication followed by a mutation (just a point mutation, I think, but I may be remembering wrong) of one of the duplicate genes. Ok, so in IDspace, the gene duplication wasn't adding information because it was just straight copying and then the mutation wasn't adding information because it was just a copying error. But at the end of the day you have a bacterium that can digest all the things its parents could digest but it can digest nylon as well. So the ID people have managed to define things such that they can dismiss any notion of increased information and hence claim that no real evolution is taking place. Well, all that suggests to me is that ID-type information is pretty irrelevant to evolution in the real world.

Albion

And in making that definition, you've specifically excluded evolution (which depends on variation of previosly existing functions) from contributing to information. In that case, it's hardly surprising that macroevolution doesn't exist in ID space, then, since it's been excluded by definition. But what have you really proved when all you've done is to define it away?

pangloss

This is probably one of the most frustrating and ridiculous issues which now seems to be the darling of the creationist/IDist crowd. As has been alluded to, the definitions of information as it pertains to biology offered by the creatioonist crowd as so vague orinappl;icable that it defies reason as to why they would actually think they even have an argument. IUn additon, the definitions employed by individual creationists seems to fold and twist as needed, depending on the issue.

In some of my 'information' discussions with creationists, the following gems have been offered (all paraphrased):


Gene duplication is not an increas eof information because it is just making more old information.

(this despite the fact that gene duplication can increase the amount of protein expressed, which can do things like alter phenotype or produce pesticide resistence)


Gene duplication followed by subsequent mutation is actually aloss of information because you are "degrading the original code"

(the nylon digestion refutes this - however, I believe this idiocy is actually borrowed from "Not by Chance" author Lee Spetner)

The only way to increase information is to increase enzyme specificity. If an enzyme is altered such that it can act on two substrates, it is actually a loss of information because it was specific for its original substrate, and making it so it can use two substrates decreased its specificity.

(no comment)


Even if a duplicated gene gains a new function, it is not an increase in information because the probablity of a change to an existing sequence is higher than the probability of the original sequence arising in the first place, and the lower the probability, the higher the information content.

(if anyone can see anything resembling logic in that, please let me know)


An insertion of a retroelement is always a loss of information because (as usual) it messes up the original code.

(I was told this after I had presented a citation for a paper in which an insertion in the promoter region of a gene in some mosquitoes caused an overexpression of a normally occurring protein and this alone provided them with a "new function" - the ability to metabolize insecticide)


Then, of course, we get all this mumbo-jumbo about "sequence space" and "universe of possibilities" blah blah blah.


Not to mention the grreatest idiocy of them all, by Werber Gitt, "information scientist", who claims in his creationist book that all information must come from a conscious mind.

If that is not an argument via definition, then I don't know what is...
:banghead: :banghead:

Oolon Colluphid

Ah good, a design argument!

Sorry, but there’s plenty of reasons to rule one out. Unless you are only bothered about the genetics of the first organism... that is, unless you are happy to leave to random mutation plus natural selection the formation of the wonderful apparent designs in nature (eyes, ears, wings and so on)... which I rather doubt... then you have to face the fact that the ‘intelligent designer’ behind these things also designed many other things very stupidly, clumsily, wastefully and pointlessly. I have a little list somewhere, if you doubt this...
Fundamental error of understanding No.1: evolution is not about accidents. Mutations are random, selection by definition is not. A slight change in the previous version may be an accident, a mutation, but whether its owner survives or not is the antithesis of random. No intelligence is needed, any more than it is required to cause certain things to pass through a sieve and others not.

For that is what natural selection is: a series of sieves. What you get out the end of a long line of sieves is stuff that’s good at getting through sieves.

What you get out of the end of the series of sieves that is natural selection is stuff that’s good at surviving and reproducing in a given environment.

To push that analogy a little further, any change in what’s going through the sieves -- say, a change that makes the sieved particles less sticky -- will get into the next round more readily, more successfully, than the stickier rivals. The stuck-together bits are on average left behind more often. Several sieves later, and the less-sticky bits are in the majority. The ‘population’ of particles has evolved.

No intelligence is required. It is simply that an accidental change can result in an utterly non-accidental effect: a change in survival and reproduction. And if (since, with genes) the change is heritable, any improvement will prosper relative to the unmodified version.
Well, if sight was designed, then how come the vertebrate retina is wired in backwards, how come the nautilus has a very good pinhole-camera eye but no lens, how come there are creatures with eyes that do not work living in places where no eye is necessary at all...?

TTFN, Oolon

Secular Pinoy

The sieve analogy is quite good, and I've used it myself. But selection implies intelligent choosing and evolution does not imply that, so I would prefer to call the process, yes you've already heard it before, Natural Filtration.

Peez

You seem to think that the protein is only capable of reacting to one specific thing. This is false. Anything that opens the channel will result in a reaction. Physically jostling it could do so, passing an electrical current through it could do so, heating it could do so, and light could do so as well if the protein has any colour. It is simply a question of the protein absorbing energy, and this energy causes it to reposition itself. Note that it still reacts to sugar, it is not (yet) specific to light (or touch or heat, etc.). Also note that all of your nerve cells will react to stimuli that are not the same as the one that they are "specific" to (pressure can cause your photoreceptors to react, electricity can cause your touch receptors to react, etc.). There is no "gigantic leap" "smuggled in" here.First, it is not that the protein is a different colour per se that makes it sensitive to light, it is simply having a colour. What being coloured means is the substance is absorbing light, which means that it is absorbing electromagnetic energy. This energy will, at the very least, cause the protein to vibrate more, which can easily cause it to change shape (a protein is a long chain of amino acids folded in a particular way, and the folding is not rigid). How the protein channel opens is it changes shape. There is no assumption being made here, big or otherwise.Please define "precursor" in this context. All the senses involve cells made up of cytoplasm in a cell membrane. You seem to be asserting that a light-sensitive protein cannot be produced by a small change in a protein that is not light-sensitive. Why? What is it about such a change that seems miraculous to you?

Peez

luvluv

Hey kids, sorry, I've been having problems with my cable modem so I'm having to switch to dial up for the time being. I've been without internet access for the better part of the week so excuse me if it takes me a while to catch up. I'm not going to let this thread die, so don't worry about that.