Deputy Dog:
If what you are saying is true, I think you are making my point
I think I must be missing your point (and you mine) but I'll try to clarify what I mean based on what I think you mean.
You highlighted my statement: Any two organisms must be in the same clade, even if it's the clade of [all life on earth].If, as it appears to be, all life on earth is related, then this statement is necessarily true. Any two organisms will have a common ancestor. If they are closely related, this will be a small clade. If they are distantly related, the smallest clade into which they fit may be extremely large and encompass most life forms. For example a horse and a donkey are obviously quite closely related and their common ancestor is quite recent (maybe a million years or so, I haven't checked). The smallest clade that includes horses and donkeys probably includes a few other species (mostly extinct) but excludes most life forms. On the other hand, an E. coli bacterium and an elephant have a very distant common ancestor (at least a billion years ago, I'd estimate) and the smallest clade that includes both of them must also include nearly every other life form on earth.
You then quoted my possible falsification of evolution:
"3) A single (moderately long) sequence of DNA that appeared in organisms from different clades but not on all organisms within a clade."
What I mean here is that there are genetic markers shared by (for example) horses and donkeys that are not shared by say, pigs. There are no such genetic markers that are shared by horses and pigs but not by donkeys (or by donkeys and pigs but not by horses. If we step back and look at the larger clade that includes donkeys, horses and pigs we find that they still share a large percentage of DNA. Again however, there is no significant sequence of DNA that is shared by say, a pig and an octopus, but not a horse or a donkey. Now, while a creator might decide to use nested hierarchies in this manner, by doing so he (she/it/they etc.) would make his creation look like it had evolved from a common ancestor. In any case, a single exception to this rule - a single example of a creator using a modular approach - would disprove the theory of common descent. None has been found.
There would be no reason for all three fields to be in such strong agreement if each species had been created independently.
Your logic escapes me here. I don't know why it wouldn't, if DNA Is what it is, the material that all living things are made (created) of
Because a creator could have used mostly the same DNA in horses and donkeys, but he could also have used a bit of the "donkey DNA" in pigs and not in horses. Given that whales and dolphins are aquatic, a creator could have used a little bit of "fish DNA" to make things easier, but he didn't - it was all mammal. He apparently "reinvented the wheel" numerous times - actually that's a bad metaphor as he never invented the wheel, too difficult perhaps? - but he apparently used different DNA to do the same tasks when animals werent' in general genetically similar. He did this right down to various quirks and errors. For example, there are several different codons (DNA "letters") that can code for the same protein. A mutation in one of these codons into another that codes for the same protein makes no difference to the survival rate of the organism but it does provide a useful marker. A creator could use whichever version he wanted in any organism, but if organisms had evolved from common ancestors, then the most closely related ones would show more similarities in these arbitrary variations. Guess what we find in nature. Do we find that these variations occur arbitrarily as if at the whim of a creator or do we find that they are nested hierarchically? The latter, of course. And while I concede that a suitably shy or sneaky creator could do this, at some point surely one has to consider the more parsimonious option, namely, that all life forms bear all the features of common descent because they are all descended from a common ancestor.
I see this as little more than selective breeding like dogs or horses
That's exactly what it's like, except instead of a person deciding which traits to keep, that is decided by nature. New genetic information appears due to random mutations. If that new information causes the organism to be better adapted to its environment, the organism is more likely to survive and reproduce and thus is more likely to survive and reproduce and thus.... This recursion may seem like a tautology but it is exactly this recursion which gives natural selection its power. There is apparently no limit to the number of times this can happen (indeed how could there be?) and with every single generation a testing ground, all the bad ideas are quickly and ruthlessly discarded while the good ideas get constantly refined and improved. After four billion years, and squillions of generations, this has produced some spectacular results.
