UppsalaDragby said:
I'm not really sure what you think is "kinda strange". Nothing in the comment you quoted conflicts in any way with my earlier comment about it being a faith issue, does it? So what do you consider to be "kinda strange"?
You said, "
there is absolutely nothing that indicates that the number of digits in any living organism should be considered the result of UCA rather than the number that a designer could have determined. So what I think you need to do is not simply provide evidence that might be considered consistent with such a theory, but to provide evidence that explains why it is the best possible explanation."
So let's clear this up. First, can you agree that when you say "designer", you're referring to God? Second, remember that I'm not trying to disprove creation by God; I'm demonstrating how UCA is a
scientifically valid and reasonable conclusion that stems from the data (the key word there is "scientifically"). If you think "design" is a plausible
scientific alternative explanation, then I need you to describe that in more detail. For example, what is the mechanism behind "design"? How can we scientifically investigate the designer, the mechanism, and other aspects of this alternative? How do we tell the difference, from a scientific perspective, between something that was "designed" and something that evolved?
And??? As far as I can see there are all kinds of things that happen in the embryonic stages of different kinds of animals that DON'T appear in the adult versions of those animals. A larv turns into MUSH before it becomes a butterfly. Does that mean it "looks like" butterflies evolved from mush? Now come on River! I can gladly agree that loss of digits might be the result of some kind of evolutionary process. That doesn't concern me too much! But whether or not tetrapods should be considered tetrapods depending on the number of digits they have is up to the classification system we employ. Isn't it?
No, whether or not something is a tetrapod is determined by the number of limbs (4) and the presence of a vertebrae.
If I was the designer and I understood all things then I guess I would have a good answer to that. But you are forgetting one very important point here! What we observe today is not necessarily consistent with the original design. As far as I can see from a Christian point of view, God did not "design" a cursed environment. He did not design sin. He did he design death. And he did not design sicknesses and diseases.
With that in mind it is practically impossible for any proponent of design to have a universal explanation that explains all the anomolies and bizarre phenomenon we see in biology. Losing digits during the transition between embryo and adult stages IS an anomoly, and yet you are treating it as though it was the norm - something we can see in all kinds of animals. We don't, so what does that "look like"? It looks like countless organisms are missing these kinds of "throw-backs" doesn't it? Why is that?
Is there any possible discovery or experimental result you can think of that
isn't consistent with "design"?
We can always pick out evolutionary explanations for these things just as we can always claim that they are a result of design. Just as I said, it is a faith issue, and whatever evidences we collect for our convictions is most likely a result of the worldview we possess.
Definitely from the creationist side, yes. That explains why all the creationists are from very specific religious backgrounds. From the scientific side however, that's not the case. There are, and have been, millions of scientists from all sorts of different countries, ethnicities, religions, etc. who have all reached the same conclusion that evolutionary theory is the best and only scientific explanation for the data. If that conclusion were entirely, or even mostly, based on a person's worldview, then we would expect scientists to break out along those lines. But they don't....at all, and that strongly suggests that the
scientific conclusions about life on earth are based on something other than worldview.
And when we look through the scientific literature we see what that something is....the data.
If it was difficult for evolutionists to point out things that "make sense" according to a theory that is very easily tweaked then you would have a point. If, rather than a loss of digits during the embryo-adult transformation there was a gain in the number of digits, rather than a loss, then there would STILL be an evolutionary explanation that any proponent of that worldview would be satisfied with. It took me about three seconds to come up with one! So what does that prove? As I pointed out, it might be some kind of throw-back.
Well, that's a nice imaginary scenario I guess, but it's not really much of a rebuttal. I'm sorry, but appealing to things you imagine might happen isn't at all convincing.
But as far as I can see there is nothing in post #197 that suggests that either of us are free from assuming that "Maybe that's just how God made things"!
And again, I'm not defending the position of "and God didn't do any of this".
No, we are not. We are not seeing evolution doing anything other than the kinds of things both of us agree on - adaption - confined within differnt families of animals.
Ah, and that's where you're wrong. If all we had to go one was the anatomical pattern among tetrapods, then you might have a point. Fortunately (and as I said earlier), there's a lot more to this story than I think you're aware of.
What actually makes the tetrapod limbs (and what makes them occur in the same patterns across such a wide variety of animals, from humans, to lizards, to whales, to birds)? By studying embryonic development we find that tetrapod limbs are made by a series of genes called
Hox genes (you probably should read and understand that Wiki entry). And when we study and compare Hox gene activity and tetrapod limb development in a variety of organisms, we see a very striking pattern of similarities and divergences. We find that at the earliest stages of development, the same genes are activated in the same ways in all tetrapods. Interesting. But when we look at fish fin development, we find that they also activate the same genes in the same ways in the same early stages! Hmmmm......
Why would fish use the same set of genes in the same ways in the early stages of fin development, as tetrapods use in their limb development? At the very least, that justifies hypothesizing that the reason is because tetrapods evolved from ancient fish, and tetrapod limb development is an evolutionary modification of ancient fish fin development processes. So we look and study more.
From the fossil record we know of a group of ancient fish called "lobe-finned fish". In the lobe-finned fish, the fins extend from the body via a stalk that is articulated to the shoulder and pelvis via a single bone. Sounds familiar, doesn't it? Not only that, but many lobe-finned fish that exist today use their fins to walk on land (e.g., lungfish)!
So based on that data, we can get more specific with our hypothesis. Not only are tetrapods descended from fish, but from a specific group of fish, i.e., the lobe-finned fish. And of course, we study even further.
Again we go back to looking at Hox genes. When we study Hox genes and limb development in zebrafish and lobe-finned fish, we see something else striking. When zebrafish Hox genes stop developing fins, lobe-finned Hox genes continue. And not only do they continue on to later stages of development, they do so in the same pattern as tetrapods! It's only in the very last stages of limb development that tetrapods continue on to make things like primate hands or bird wings.
So you see the pattern. Finned-fish, lobe-finned fish, and all tetrapods start off with the same early limb developmental processes, including using the same set of genes. Lobe-finned fish and tetrapods share the same later limb developmental processes, including the same set of genes. Tetrapods share the same late limb developmental processes, including the same set of genes. This pattern and the genetic data behind it is entirely consistent with our hypothesis that tetrapods evolved from ancient lobe-finned fishes.
Ah, but we're not done yet!
Naturally if our hypothesis is accurate, we would expect to find some evidence of this evolutionary history in the fossil record. And we can even get reasonably specific with our expectations. From the fossil record, we see that ~400 million years ago (MYA) there were no tetrapods, but there were fish (including lobe-finned fish). But later on the record shows the existence of a handful of primitive tetrapods ~350 MYA. So from this information, we predict that we should be able to find fossils showing the transition between lobe-finned fish and early tetrapods, and those fossils should occur between 350-400 MYA.
So paleontologists go out and start looking. And I think you know this part of the story....they found exactly what was predicted! We have a very, very good series of fossil specimens from that time showing stages of lobe-finned fish to tetrapod evolution. I'm not going to describe all of them (because there's a lot of 'em), but you can look at the following to see what I'm talking about.
Wiki Page
UC Berkeley
And if you'll notice, even in those fish-tetrapod transitional fossils we see the same bone pattern...one bone, two bones, little bones, digits. But wait, there's yet another pattern! The fossil record also shows the following pattern as we move forward in time...
Lobe-finned fish, but no tetrapods
A few lobe-finned fish--tetrapod transitionals
A few primitive tetrapods
More early tetrapods
A continued period of tetrapod diversification
This pattern can even be put into graph form. (It's too big to post here, but you should really go look at it)
Ok, we now have strong supporting evidence from genetics, embryology, anatomy, and the fossil record supporting our hypothesis that tetrapods evolved from lobe-finned fish between 400-350 MYA. On that basis we can say that our hypothesis is supported by the data from diverse fields of science, and therefore it's reasonable to conclude that it's accurate.
But even if we conclude that all this
did happen, that still doesn't address the question of
how it happened (or more to your original question about if it's genetically possible). To answer that we go back to our earlier discovery of Hox gene expression patterns. As you should know by now, Hox genes occur in clusters, and different taxa have different clusters of Hox genes and regulatory regions. And specific to this issue, we also notice that many of these clusters and regulatory regions look an awful lot alike. In fact, they look exactly like some of them are modified copies of other Hox clusters. So we hypothesize that at least one of the evolutionary mechanisms behind the transition from lobe-finned fish to tetrapod genetic copying and rearrangement.
Remember the example I showed you earlier where a population of yeast copied different parts of different genes and re-arranged the copied bits into new functional genes? Those results (and they're not the only ones demonstrating this concept) show that the mechanism we hypothesize above is not only possible, but actually happens. Ah, but we're still not done! Scientists have actually taken modern fish and, by exposing their embryos to certain hormones, changed the Hox gene expression pattern in fin development. The fish ended up developing the early stages of tetrapod limbs! So yet again we have experimental results that support our hypothesis.
Of course this doesn't mean that scientists have the entire step-by-step history of the evolution of tetrapods figured out. There's a lot more to work on, and there are competing scenarios for different aspects. With that said however, hopefully from the above you will get a basic idea of some of the data and why scientists have concluded that tetrapods are the evolutionary descendants of lobe-finned fish.
We can always go back and start disussing definitions of kinds and species if you want, but the fact remains that the evidence of UCA is extremely weak and is subject to the worldview that one adheres to.
I'm sorry, but that's simply not true. First, you are in no position to authoritatively declare what the data is or isn't in evolutionary biology. That's just a fact. Second, as I explained above, the diversity of "worldviews" among scientists who, over the last 150 years or so, have reached the same conclusions about the evolutionary history of life directly contradicts your claim.
There's no other way to put it Uppsala...you're wrong, and
demonstrably so at that.
Oh what rubbish! The very fact that you claim that "all we ever see is evolution" testifies to the fact that you only "see" what evolutionists dictate and ignore the rest.
That's a pretty serious accusation. Do you have anything at all to back it up?
If all we see is evolution generating new traits, abilities genetic sequences.. and so on... then we WOULDN'T see any living fossils, would we?
Sure we would. But if you're disputing the conclusion that the only mechanism for generating new biological traits we've ever seen is evolution, then what other mechanism for generating biological traits do you think we've witnessed?
But boxing these things into an "explanation" is a convenient way of pretending that everything we see is evolution! As I pointed out, what you "see" as evidence of evolution, I see as evidence of design - that God designed living organisms with the ability to adapt to changes within their environments.
And by what non-evolutionary mechanisms do these organisms adapt and develop new traits?
One of the first things that Genesis teaches us about life is that God created it according to his own classification system
No it doesn't. It says God let the earth produce living things that later
reproduced "according to their kinds".
Now we could have another disput about whether or not animals such as amphibians live on land or in the sea, but the fact remains that there is nothing within the realm of science that demonstrates that any kind of living creature completely changed from living in one distinct environment into another. What it all boils down to is what we think we "see".
See above. You're just plain wrong.
OK, so who is advocating "constant tinkering"? I certainly am not, so I don't know where you get that idea from. A complete working system MUST be tinkered with at some stage, otherwise how on earth would anyone consider it to be a creation?
Which is a more complete creation....one where God says "let the earth bring forth life" and the earth brings forth life, or one where God says "let the earth bring forth life" and He then has to go and create life Himself?
So what you are trying to say is that life today is exactly the way God made it in the beginning. Doesn't seem to support evolution at all does it? And quite OBVIOUSLY your argument bounces back in your face, since you can always claim that "evolution made it look that way" (just as you did with the number-of-digits argument earlier on).
I'm sorry, but that response make no sense to me.