One way to tell that organisms are different, is that they can no longer interbreed. One of the predictions of evolution is that if one species was geographically separated into two different habitats, with different demands on the organisms, that eventually, these organisms would no longer be able to interbreed. Have we observed this?
We haven't just observed reproductive isolation, we've made it happen in the lab, with flies. Usually associated with behavioral and physical modifications too. In the wild most observed cases involve plant hybrids or polyploidization events, because that's the fastest way speciation can happen. Then there are cases where we know speciation happened very recently (through historical knowledge but also genetic analysis) and involve dramatic changes in behavior and morphology, in cases such as the African cichlid fish or animals that colonized archipelagos. Note that "very recently" can be very
recently : house mice were introduced to the island of Madeira just a few hundred years ago, and now over a hundred different reproductively isolated groups exist with different morphologies and different chromosome counts. And then there are groups that speciated so gradually they constitute ring species, where every adjacent population can interbreed with each other one but the two populations at each end can't. In this case we still see every intermediate of the speciation event although the event itself happened already.
The issue with speciation is that genetic incompatibility usually comes about through genetic drift, and that happens at a constant rate that can't be forced (except by increasing the mutation rate, which doesn't happen a lot). So the African cichlid fishes for example are very similar genetically - it's unknown whether they'd be genetically compatible, but as far as reproductive isolation goes it's moot because they have complex mating rituals that mean they never mate outside their own species.
I believe you are trying to play a word game and confuse concepts which I am communicating clearly. The "completely different organisms" was qualified, in the same sentence, by the phrase "that cannot interbreed". In bacteria, since they do not reproduce s*xually, there should be other ways of distinguishing between kinds. There is no universal distinction for this in the bible, but I would say prokaryotes and eukaryotes are different enough that they would be considered completely different organisms. This is why I used this example.
I'm sorry you think I'm playing word games; I sincerely don't know what you mean by "completely different organisms". "That cannot interbreed" doesn't narrow things down because there are plenty of groups that cannot interbreed but that I think are very similar. And using prokaryotes and eukaryotes as an example of "completely different" is more confusing still, because prokaryotes and eukaryotes are more different than any two eukaryotes you could come up with. Yeast are more like humans than they are like bacteria. If we take prokaryotes vs eukaryotes as our template for "completely different" then we've got a scale on which humans and tunicates are substantially similar. I don't think that's the scale either of us is interested in.
This statement is not very specific. There are living fossils which, according to evolutionists assessment of the fossil age, have not changed much at all over millions of years. Your statement assumes the accuracy of the "geologic column" dating, which is debatable. Also, there are a wide variety among living organisms, so finding fossils of extinct organisms does not necessarily indicate that genetic mechanisms could explain common descent.
When we look at fossils, we see that different layers have systematically different fossils. Yes, some fossils span a lot
of layers but most don't, and that doesn't change the point that the overall fossil composition is different for each layer. No need for radiometric dating to see that.
And yes, there is a wide variety among living organisms today... But the species makeup of today's biosphere isn't what we see in the fossil record. The highest layers have a species makeup that's very much like today's, and each layer has a species makeup very much like the one above it (with a few exceptions, but even those show a continuity in the kind of species both layers contain), but as we go deeper they get more and more different and fossils that even resemble modern species get more and more rare.
That is exactly what this thread is inquiring about. Proof that there is no genetic limitation is not proof of evolution, it just means that evolution remains possible, but then so does creation.
That is indeed what this thread is inquiring about. And that there is no genetic limitation to species change is indeed not evidence that species actually have changed that much. The evidence for that is the patterns of morphology and genetics we see and what we see in the fossil record.
And creation is always possible. God could have done anything and made it look like anything. If all you're concerned about is that creation be possible then there's no need to look for evidence for or against it.
I would love some evidence that eukaryotes formed from prokaryotes, but you consider this to be unreasonable.
Sorry, I misspoke. I meant that expecting that event to be reproduced in the lab
is unreasonable. As for evidence that it happened, there are genetic and metabolic homologies between eukaryotes and some prokaryotes for one, and genetic and morphological evidence that mitochondria and chloroplasts evolved from endosymbiotic prokaryotes.
As far as I know, this would be the only sign of evolution in prokaryotes.
That's your eukaryotic bias speaking. Prokaryotes are much more diverse amongst themselves than eukaryotes are; I'm pretty sure they're also more diverse amongst themselves than they are different from eukaryotes. Yep, checked Wikipedia : archaea are more like eukaryotes than they are like bacteria.
I wasn't joking when I said I'd seen bacteriologists say there had been no evolution in eukaryotes since they'd arisen. Bacteria have much bigger differences in basic things like cellular metabolism than eukaryotes do.
I am looking for a gain in a new function in organisms, like I said. I believe this last sentence is a straw man. I never said that a gliding squirrel could not come from a jumping squirrel (or vice versa). I would say that plausibility that wings can form in stages is not proof that they did.
Sorry, I didn't mean to make a straw-man, I just wanted to point out how completely different what you were asking was from what I assume you're really interested in (evolution among animals). After all some people believe that eukaryotes and prokaryotes were specially created but everything after that came through evolution (mostly because of how unlikely the evolution of eukaryotes appears to have been). They're separate questions, really.
And I'm sorry but I still don't know what kind of gain in a new function you're looking for. You yourself suggested such a new function (digesting nylon) and rejected it because it was the modification of a previously existing function. But the modern theory of evolution requires
every new function to be a modification of a previous function. If we ever find evidence of a new function arising with no relation to previous functions, evolutionists would be as baffled as you
. It would be evidence against
the theory of evolution in its current form. (common descent is about the only aspect of the theory of evolution that wouldn't affected much either way)
So I really don't know what to tell you here.
I think this topic is in danger of being derailed. The point of this thread was not to rehash the entire creation vs evolution argument, rather to inquire if there are any genetic limitations to evolution between kinds.
Sorry; obviously that's something I can't address. But dismissing nylon-digesting bacteria because it's a modification of a previous function is a serious misunderstanding of the theory of evolution so I felt I had to address that.