If you study the development of centipedes you might find out that all the segments are related so if legs evolve on one segment, it’s more than likely the other segments will also have legs.

http://www.salk.edu/labs/mnl-t/clh/pede2.html

I have a related question. Is it possible in principle for a vertebrate to develop a functional set of extra limbs? Like, a bird with an extra pair of wings? I realize nothing like this has ever actually happened, or if it has there apparently isn’t a fossil record of it, but is there any concrete reason that couldn’t happen?

Hmm well it’s not quite the same but search Google for the dolphin that has pelvic flippers.

There are also quite a few cases of children born with an extra arm or two, so yes it is possible.

On the worm / centipede front, research onycophorans.

Just because worms don’t have legs, it doesn’t mean they don’t have appendages. Look at polychaete annelids.

@homeworkkid

Look up hox genes and what they’ve done with fruit flies.

The question was "Can an organism develop an extra pair of functional limbs?" and the answer is yes, but depending on how the mutation happened your limbs might not be in the spots you want.

But what you want to know is about an example of an adaptation of a functional component that is also beneficial? Well lookup the panda’s thumb. Dr Gould had a whole book dedicated to that subject.

How can you tell that it’s a mutation? Morphology.

The genes for related but different physical structures are themselves related but different, but the timeframe means that we aren’t seeing the actual transitions, we’re reconstructing them.

or you can always do DNA comparison between worms centipedes and whatever and get a phylogenic tree to show who originated from who. There are a lot of premade models of mutation, gene drift and all the other evolution causing agents. You basically then compare your data to them.

Right, so we examine a panda’s paw. At the place where there is supposed to be a wrist bone we find an enlarged bone that functions as a thumb. What conclusions can we draw?

What do you mean by just created that way? Are you proposing that pandas are created and unrelated to anything else genetically?

http://www.talkorigins.org/faqs/comdesc/

Come back with specific questions when you’ve finished reading up on how phylogenetics, radiocarbon dating and evolution works. Otherwise we’ll be talking in different languages.

How about this: Rather than turning this into another creation/evolution "debate" why don’t we just continue to address the original topic? It’s an interesting question, and one I’d like to see explored more.

It’s a poor analogy because no one claims that potassium and chlorine are the "parents" of salt. But composition-wise you’d have to agree that one is created from components of the other. Somehow somewhere potassium and chlorine have to be involved to make KCl.

And to me it seems more like you don’t quite understand how relatedness is compared. You say that mice and men have 90% in common. I’m not sure if the number is accurate but for the sake of argument lets say it is. But because there are only 4 bases , if you have two unrelated sequences you still get 25% similarity. So what does a 90% or 95% threshold of similarity mean? Is 90% really closely related or not?

Plus you specified that the genes are 90% common. Some 95% of your DNA is non-coding. Are those differences going to be a factor?

We’ve seen the hox gene being mutated to create whole legs in fruitflies, how hard would it be to enlarge a wrist bone? Granted the fruitfly is a lot more simpler, but why can’t the same mechanism be used to explain the panda’s thumb?

Let’s say that epigenetics was at work here. What is the extent of its power? Do we have analogous cases ? If everything could be explained through epigenetics why do we have different DNA?

The "kinds" argument has more holes in it than a sieve. First of all, how do you define "kind"? Is it a genus? A family? An order? No one has ever given a clear definition, and I suspect it is so that they can simply wait for proof of an evolutionary lineage to be proven, and then claim that it doesn’t matter because all the species involved are of the same "kind." I could just as easily claim that all vertebrates are the same "kind," and so it should be no problem to accept man’s common ancestry with apes. It’s a simple yet illogical fall-back argument that you can cling to even when your case has been disproven. I’m sorry, but in this forum we’ll need legitimate scientific theories, and scientific terminology, not vague references to "kinds."

And since you mentioned the Bible, I would suggest you read it a little more carefully. I’ve read Genesis more times than I can remember and I am at a loss to figure out where it disagrees with modern scientific theory. In fact, the two are remarkably compatible.

You know what, on second thought, you’re right. Perhaps we could start a thread in the off-topic to handle the debate that this has become?

Are you saying it’s not meaningful to classify the polar bear and the grizzly as different simply because they can interbreed? I assure you, just because there are many definitions and some of them ill fitting does not mean they are useless.

For example some fruitflies are categorized based on the tufts of hair on their middle legs which seems really bizarre but has uses for conservation purposes. Likewise the morphological definition might be used for telling between a wolf and a dog. There’s no use trying to see if a dog and a wolf would mate if you’re confronted in the Alaskan wild.

I admit there is some debate over the exact definitions of scientific terms, but it is clearly understood that species are subgroups of genera, which are subgroups of families, which are subgroups of orders, etc. While there remains some difficulty with certain taxa as to which group or the other they should belong to, for the most part these taxanomical terms have very clear meanings. No one is going to hear "class" and think it means "family." What I ask you to do is tell me exactly which taxanomical level is equivalent to a "kind"; only then can we determine if your arguments have any scientific value or not.

You need to take into account that Wikipedia can be edited by any retard with an internet connection. "Often" is the key word; that definition does not apply to all organisms. For example, it would be pointless and silly to try to categorize asexual species based on whether or not they can interbreed.

Had you read just one more paragraph, you would have found:

As good as it is, this definition is troublesome for organisms that are non-sexually reproducing, for those known only from fossils, or when life histories have not been studied.

As I said before, simple interbreeding is not the only way – nor is it a fully reliable way – to differentiate species.

I already read the species article, and if you scroll down you’ll see the nuances I discussed in my previous post.

So are you implying that "kinds" equals "species"?

Oh please. The word ‘species’ is used by scientists specifically because its meaning is more refined and definable. "kind" can imply ANY relation.
Scientific language is used with the specific intent to narrow down and winnow out extraeneous meanings and thus confusion. So IF YOU WOULD tell me what taxonomic level you are indicating when you say "kinds" and we can continue our SCIENTIFIC conversation from that point.

http://www.talkorigins.org/faqs/faq-speciation.html

Here’s a quote:

The site goes on to list several observed cases of speciation, but I believe the species definition that it gives is perhaps the best one currently available. Basically, it is a population that reproduces. If we are to take the grizzly and polar bears as an example, they would be two separate species, since they do not breed with each other in the wild; they are thus two separately reproducing groups. The same could apply to Darwin’s finches.

Now could you please tell me which taxanomic level is meant by "kind"?

Perhaps in a few rare cases they might, but for the most part they do not.

I’m sure if you turned off a few human genes and re-expressed others, a human embryo could develop into a chimpanzee, and yet both are different species. But that sort of thing doesn’t happen naturally.

Ok sport, you are setting up a straw man here. There are different ways to define species because there are different forms of life. As was pointed out earlier, you wouldn’t want to define an asexual species by what it can or can’t reproduce with.
You have to take a larger ecological look at the populations in question. Each individual species should have its own unique ecological footprint.
By now you’ve probably looked through all the different species concepts and know that "viable offspring" is not the only way to define a species.

So you say it’s vague and subjective, because the rules set down to define species don’t always work in every scenario.

The key is that there ARE rules though, and they can be very detailed. To declare a species, a scientist must undergo rigorous taxonomic definition and then be subjected to peer review.

Do you really think that science (specifically biology and ecology) would have been able to accomlish what it has if we did no more than identify "kinds" of organisms?

I can see it now, the doctor has a patient with a severe infection so he grabs a piece of bread with mold on it and smears it all over the infected area and makes the patient eat the rest. "Hey it’s the fuzzy kind of mold, don’t worry!"

No sir, "kind" is a cop-out because you’re unwilling to aquiesce to the validity of taxonomy, BECAUSE, taxonomy is *gasp* based (at least in part) on evolutionary theory.
I’m not saying it’s perfect (ie polar bears and grizzlies, dogs and wolves), but it’s valid. It’s a system that is capable of correcting itself.

Go ahead, test it. Do an internet search for "Rhinichthys osculus".
Now do a search for "little fish" or "minnows" or "spotted minnows" or "little spotted fish"
Heck do a search for "things that swim"
Those are all "kinds"…

I’m not sure what you’re trying to prove by claiming the word "kind" is on par with taxonomic nomenclature, or other valid systems.

Really I’m at a loss as to what your point is with the whole "kinds" thing.

Oh and with the grizzlies, etc. So it’s vague as to where the species line is going to be drawn… so what? If they’re declared the same species (which i think they are) they will still be given different subspecific eptithets. They will be differentiated in their names, as they should be, because they typically live in very different ecosystems and have very different lifestyles.
I believe how I learned it was that Polars are Ursus arctos arctos and Grizzlies are Ursus arctos horriblis. The point is that no scientist is going to call them the same exact animal.

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