DNA, PRO or CON for Evolution

[Milken]

I feel like you are tackling a bunch of issues so I'm breaking this up into points:

 

1) Homology is when a specific trait is structurally similar in different organisms due to descent from a common ancestor' date=' right? So, yes, by definition, homology is evidence that evolution occurred. In mutation accumulation experiments, it is possible to verify in "real-time" that homologous traits do occur. [/quote']

 

Yes, I disagree with something scientifically being true by definition. Like saying "Because I said so". The real definition is "homology- the science of similarity", especially since homology was invented by a non Darwinist, with the intent of showing common design.

 

2) Is homology the only evidence for evolution? Of course not! But I'm pretty sure you already knew that' date=' so I'm wondering why you bothered to ask that question. If you really didn't know that, then I suggest you do a google search for the various kinds of evidence that support evolution. I've already mentioned one (mutation accumulation experiments).[/quote']

 

I've heard of other evidence, everyone kept taking about the samething.

 

3) I believe your conclusion that' date='

 

is logically incorrect.

 

Similar genes are homologous if they are derived from a common ancestor. There are many mechanisms that "cause" homology in DNA sequences: divergent natural selection of different organisms, gene duplication events coupled with mutation accumulation, mutations that change the coding in areas that don't affect function, genetic drift, etc. Likewise, developmental pathways are homologous if they derive from a common ancestor. [/quote']

 

How does two genes being similar prove they came from a common ancestor? It's an inference.

 

 

But it's illogical to say that developmental pathways and similar genes cause homology. Because' date=' as Halucigenia said, they could be similar because of convergent evolution, not because they are homologous. (Convergent traits are "analogous".) Does that make sense? [/quote']

 

Well, evolutionists definitely have different views, so some have illogical views. The article was mentioning similarity not specifically homology. There's a difference. Convergent evolution is another way of saying they're similar and it's a coincidence. The examples have similar/interchangeable genes, and different look/method of function.

 

4) Now' date=' if your question is, why are sequences assumed to be homologous if we don't have direct evidence? That's an interesting question. As stated before, we have physical real-time evidence that all the "mechanisms" of evolution occur - i.e. mutations, migration, natural selection and genetic drift. We also have physical evidence that homology occurs.

 

So, we use the information derived from the physical evidence to make assumptions about how evolution is occuring. For example, we could say that every single type of change that could occur will occur with equal frequency (e.g. point mutations, transversions, transitions etc.) Alternatively, we could say that certain changes occur more frequently than others (e.g. G tends to be mistaken for C more often then A). Then we make a model that fits the assumptions. Then we compare our sequences using that model.[/quote']

 

The physical evidence shows slight anatomical change, that, with fossils involved is extrapolated into timing when traits evolved via molecular clock, This also being done on the assumption that it happened in the first place.

 

I'm not going to get into all the different ways you can model evolutionary history and thereby answer the question' date=' is the trait homologous? If you're interested, I suggest you look up "parsimony" and "maximum-likelihood" to start you off. [/quote']

 

I know, it's intricate. I will.

 

5) My last point is that I don't think that anyone ever says' date=' "this tree is proof that these organisms are homologous". What they say is, "this tree shows poor/strong evidence that these organisms are derived from the same ancestor. Moreover, other evidence supports this hypothesis as well, blah blah blah.[/quote']

 

NO! I don't think anyone is THAT stupid!lol

[Halucigenia]

Not the same type, basically the exact same type. Part of Neo-Darwinism suggests homology is due to the genes. Your statement seems to contradict this, help me out.

Certainly, I don’t contradict the fact that sometimes homology is due to genes, just that, as I pointed out the example of the mammalian/squid eye is not an example of homology. The homeobox genes are involved in “patterning” the development of organisms not in the development of specific functions, features or tissues. This is what makes them reusable in different types of organisms, from mammal to squid with similar types of eye, to insects with very different types of eye. The organisms in question have not had to re evolve their homeobox gene, just use it in different ways to produce novel, sometimes similar by convergence not homology, eye structures.

The statement says the same gene not genes (maybe a mistake). This co-opting involves more than just tissue right. So, the same gene co-opts different eye structures in different animals. How does that "prove" the eye evolved? If your statement is true, it proves that the a single gene does not have autonomy over a trait. Which suggests DNA has an overall blueprint already in mind, that makes the tissue form properly.

I was using the plural as there are many genes that have homeobox sequences, it may be that there is a single gene (singular) that is identical in many organisms that us used for eye development, but I doubt that this is the only gene involved. The same gene co-opting different tissues and circuitry etc. facilitating the evolution of novel optical structures that are used for similar function does not suggest an overall blueprint IMHO, but suggests a complex flexible interaction of processes with no pre determined goal, just as one would expect from evolutionary processes.

It's difficult to detect the exact motives of a designer, I never met'em. In everyday life the same 'general' process is often used to make different things via different materials. Not a big deal to me. . .

The point is that these examples are not variations on a single design using different materials, but totaly different "designs" that look superficially similar, not something that you would expect from a single designer. I was just comparing the pro for evolution with a con for an alternative - design. If there is an alternative explanation for DNA other than evolution I would prefer an explanation that actually explains someting, design just does not provide an explanation IMHO. You do not seem to be offering any alternative explanation.

Did I say the octopus didn't count?

Post #9.

I'll need a better example than a squid it doesn't count.

I just rate the squid's eye as a good example myself.

Convergent evolution' date=' the eyes are only similar in that they see, and controlled by the same interchangeable gene, doesn't show much change. [/quote'] No, I think that you misunderstand, the mammalian eye and the squid eye are very similar in form but have significant differences in anatomical detail. This shows a huge amount of change.

Since they don't have a common ancestor the genes shouldn't be so similar, unless genes do not necc account for similarity.

The point is that they did have a distant common ancestor, shown by the similarities of those homeobox genes and their DNA in general, however these particular genes do not account for the similarity of the eyes as they do not have a common ancestor with a common structure for the eye, the eyes evolved independently.

In this case it is the fact that the DNA has similarities, but that these similarities do not cause homology that refutes your argument

Is homology the only DNA "proof" for evolution?

this is what I was getting at.

[jeskill]

Yes' date=' I disagree with something scientifically being true by definition. Like saying "Because I said so". The real definition is "homology- the science of similarity", especially since homology was invented by a non Darwinist, with the intent of showing common design.

[/quote']

 

I think you misunderstand and are confusing the definition of homology with structures that are homologous. We define what homology is and then look at structures and test if they're homologous. But structures aren't homologous by definition.

 

I've heard of other evidence, everyone kept taking about the samething.

Seriously, look at mutation accumulation experiments. Some authors have sequenced parts of the genome before and after the experiment and have found differences in the sequences that can only be attributed to mutations.

 

How does two genes being similar prove they came from a common ancestor? It's an inference.

 

That's exactly my point. Similarity does not equal homology. Similarity can occur because of convergent evolution. That's why you have to be really careful when you're picking which traits to compare when constructing an evolutionary history.

 

 

 

Well, evolutionists definitely have different views, so some have illogical views. The article was mentioning similarity not specifically homology. There's a difference. Convergent evolution is another way of saying they're similar and it's a coincidence. The examples have similar/interchangeable genes, and different look/method of function.

Convergent evolution is not a coincidence -- it occurs when two different organisms evolve in similar habitats. For example, cacti and euphorbia look very similar, but their traits are not homologous. Rather, both plant clades live in harsh desert environments and have adapted similar features to deal with it. If you look at the DNA sequence of genes encoding for convergent traits, the sequences will invariably be completely different.

 

 

The physical evidence shows slight anatomical change, that, with fossils involved is extrapolated into timing when traits evolved via molecular clock, This also being done on the assumption that it happened in the first place.

The physical evidence also shows genetic change over time, not just anatomical change. Again, look at mutation accumulation experiments. (Sorry, I'm just really into the coolness of those experiments ).

I think you're using the word "extrapolation" incorrectly. Fossils are dated using particular methods and compared with molecular data. I don't think anything is "extrapolated".

 

Re: you're last statement: assuming what happened in the first place?

[jeskill]

I think Halucigenia makes a great point that it'd be unlikely that a designer would design parallelisms (ie. traits that look similar and have similar functions but are encoded differently).

 

Think about the cactus/euphorbia example: It would make sense that a designer would use the same genetic code to code for a particular functional trait. Why create two organisms with the exact same trait that's encoded by a completely different DNA sequence? What a waste of energy!

 

The alternative is that the two organisms evolved the same function independently of each other, but each did it in a different way.

[Skye]

Milken, "evolution" (as in the underlying theory) is a model that is used to understand and describe biological phenomena. Like any scientific theory there is no proof, just a certain authority accumulated by the consistency of the model with observed phenomena and due to its ability to describe those phenomena within a broader context. I'm sure you've read this sort of thing before, so where's the problem?

[Edtharan]

If you accept that DNA controls the development of an organism, that DNA can mutate, and, that an organism that has developed traits that give it an advantage in its environment will tend to produce more offspring in its life than other members of its spiecies, than the only conclusion is that DNA is pro evolution.

 

If you accept these 3 points, than that is all you need for evolution to occure. All of these have been demonstrated in the lab and in wild populations. Therefore DNA has to be PRO evolution.

[Milken]

Certainly, I don’t contradict the fact that sometimes homology is due to genes, just that, as I pointed out the example of the mammalian/squid eye is not an example of homology.

 

I agree it's not homology that's why earlier I was pointing out the difference to someone else, the gene is similar.

 

The homeobox genes are involved in “patterning” the development of organisms not in the development of specific functions' date=' features or tissues.[/quote']

 

What's the difference between "patterning" and development of specific functions, features, or tissues? What does the later? Basically I'll have to look into, definitely worth learning about.

 

I doubt that this is he only gene involved.

 

Well' date=' I don't know if Jonathan Wells is incompetent or not.

 

The same gene co-opting different tissues and circuitry etc. facilitating the evolution of novel optical structures that are used for similar function does not suggest an overall blueprint IMHO, but suggests a complex flexible interaction of processes with no pre determined goal, just as one would expect from evolutionary processes.

 

In other words, the gene isn't soley responsible for similarity like some Neo-Dist postualated.

 

I was just comparing the pro for evolution with a con for an alternative - design. If there is an alternative explanation for DNA other than evolution I would prefer an explanation that actually explains someting' date=' design just does not provide an explanation IMHO. You do not seem to be offering any alternative explanation.[/quote']

 

I thought the explanation is that it looks designed as opposed to it looks like we came from a bacteria. I don't see one being that much stronger, but really I'm looking at pro/con evolution.

 

Post #9. I just rate the squid's eye as a good example myself.

 

My point was that the squid is not a good example of the inverted part of the eye. The invertation causes a blind spot in animals with two eyes but they don't overlap and the inverted part allows more oxygen which is neccessary for the vertabrate eye. Squids aren't vertabrates and they only have one eye so the way the look(almost said design lol) makes sense. Thus' date=' it is a bad example.

 

The point is that they did have a distant common ancestor, shown by the similarities of those homeobox genes

 

Stop, the similarity proves they're similar, not that they had a common ancestor. It proves the gene has always been around or is old though.

 

and their DNA in general, however these particular genes do not account for the similarity of the eyes as they do not have a common ancestor with a common structure for the eye, the eyes evolved independently.

In this case it is the fact that the DNA has similarities, but that these similarities do not cause homology that refutes your argument this is what I was getting at.

 

It's not me that says similarity is in the genes. It's Neo-Darwist. They're arguement is refuted. It also seems evident similarity does not prove common descent because some physicaly similiarites count(cladists) and some genetic similiarities don't count. I need to regroup and flesh this outlol.

 

As for the designer/materials comment. It's resonable for a designer to use the same thing to produce something different. Look at the materials of different kinds of anything, like buildings, a dog house to skyscraper. Anyway, not really the point of the thread. . .

 

You've made some interesting points I think we may be using different definitions on some terms, similarity and homology.

[Halucigenia]

Squids aren't vertabrates and they only have one eye so the way the look(almost said design lol) makes sense. Thus' date=' it is a bad example.

[/quote']Suddenly loses what little credibility I gave you ... though I may deign to reply if I can be bothered.

Squids aren't vertabrates..... but octopi are I suppose

The point was that cephalopods are very distant relatives to mammals.

One eye LOL, what makes you think this?

(Only bothering a bit)

[Edtharan]

Squids aren't vertabrates and they only have one eye so the way the look(almost said design lol) makes sense. Thus, it is a bad example.

Yes squid are not vertebrates (backboned animals), they are cephalopods (related to the snail and slug). They are invertebrates (without backbone).

 

Squid have 2 eyes, not 1.

 

Squid and other cephalopods (if you take evolution) share a common ancestor with mamals (mamals are a vertebrate). But this ancestor did not have a functioning eye. The development of the eye in cephalopods and mamals occured after they split from the common ancestor, so the eyes that they have can not be evolved from a common eachother. They eye evolved in these two lineages seperately.

[Milken]

I think you misunderstand and are confusing the definition of homology with structures that are homologous. We define what homology is and then look at structures and test if they're homologous. But structures aren't homologous by definition.

 

I was going by the definition you posted on the first page:.

 

1) Homology is when a specific trait is structurally similar in different organisms due to descent from a common ancestor, right

 

which was my initial understanding. I do see your point though and it's an important and subtle distinction to make. In testing to see if structures are homologous, you're basically just seeing how similiar they are and using the molecular clock, right? What does two structures being similiar have to do with saying common descent is a fact?

 

I hate to have to go back and "figure" it out but I believe the info I posted from Wells uses similarity, not homology. People have seemed to respond using homology as if it's the same thing as similiarity.

 

 

Seriously' date=' look at mutation accumulation experiments. Some authors have sequenced parts of the genome before and after the experiment and have found differences in the sequences that can only be attributed to mutations.[/quote']

 

Well, I agree mutations happen. If I didn't I'd be an IDiot.

 

That's exactly my point. Similarity does not equal homology. Similarity can occur because of convergent evolution. That's why you have to be really careful when you're picking which traits to compare when constructing an evolutionary history.

 

So' date=' do you thing similar genes account for homology?

 

Convergent evolution is not a coincidence -- it occurs when two different organisms evolve in similar habitats. For example, cacti and euphorbia look very similar, but their traits are not homologous. Rather, both plant clades live in harsh desert environments and have adapted similar features to deal with it. If you look at the DNA sequence of genes encoding for convergent traits, the sequences will invariably be completely different.

 

That's the same definition of convergence I'd use. Not that convergent evolution is coincidence but the similarity is not due to homology that's all.

 

The physical evidence also shows genetic change over time' date=' not just anatomical change. Again, look at mutation accumulation experiments. (Sorry, I'm just really into the coolness of those experiments ).

I think you're using the word "extrapolation" incorrectly. Fossils are dated using particular methods and compared with molecular data. I don't think anything is "extrapolated".

 

Re: you're last statement: assuming what happened in the first place?[/quote']

 

No, I used extrapolation because I was poking a little fun at the process = ). Assuming that they descended from a common ancestor.

[Milken]

Suddenly loses what little credibility I gave you ... though I may deign to reply if I can be bothered.

Squids aren't vertabrates..... but octopi are I suppose

The point was that cephalopods are very distant relatives to mammals.

One eye LOL' date=' what makes you think this?

(Only bothering a bit)[/quote']

 

LOL, We both made a mistake. I thought they were so similar. . . I just ASSumed. My point was that the vertabrate eye requires more oxygen with is aided by the inverted retina. What's wrong with you? You gave me a little credibility, why would you do such a foolish thing? You're a disgrace to all hardcore 100% convinced Evolutionist.

[Milken]

Suddenly loses what little credibility I gave you ... though I may deign to reply if I can be bothered.

Squids aren't vertabrates..... but octopi are I suppose

The point was that cephalopods are very distant relatives to mammals.

One eye LOL' date=' what makes you think this?

(Only bothering a bit)[/quote']

 

LOL, We both made a mistake. I thought they were so similar. . . I just ASSumed. My point was that the vertabrate eye requires more oxygen with is aided by the inverted retina. What's wrong with you? You gave me a little credibility, why would you do such a foolish thing? You're a disgrace to all hardcore 100% convinced Evolutionist.