Evolution, religion, and ignorance.

[Chas]

I would have to disagree with the supposition that once you've demonstrated microevolution you've thereby demonstrated macroevolution because macroevolution is "just more of the same." That's an unscientific assumption that a trend will, left to its own devices, continue in the same direction and at the same pace. This isn't a valid assumption in the general case, and it's not valid as an assumption in this case. We don't know enough about the mechanics of genetics to say that there are no limits to variability at the biological level "based solely on observation of microevolution in existing genetic populations." The conclusion that macroevolution occurs is one based on a pattern of evidence, it's an inference from a lot of evidence. In that respect, it is categorically different from microevolution. We can see microevolution and demonstrate it in the lab. The same can't be said for macroevolution; it must be inferred from a pattern of evidences. Thus I think there is a real barrier to both the demonstration of macroevolution, and the acceptance of it, which doesn't exist with microevolution. Both can be demonstrated to occur, yet the demonstration of macroevolution is categorically different from the demonstration of microevolution, and with that difference enters the possibility of doubt of the former, while simultaneously accepting the latter. This is not just pigheaded refusal to accept that microevolution and macroevolution as being the same; it's an acknowledgement that the evidence for one and the evidence for the other are unique. One can withhold assent for macroevolution without being inconsistent in one's acceptance of microevolution, and I don't think the burden is necessarily on the skeptic of macroevolution. If the evolution advocate's position is simply assuming that the trend of microevolution can extend beyond the boundaries of species, then he or she needs to demonstrate it with more than an assumption of uniformity of trend.

I'm afraid the burden is still on the denier to present a mechanism that limits change.

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Now, stop. If something is observed to happen, and we have evidence of it happening, then is that not reason enough to infer that it will continue to happen, without the intervention of some outside force?

No, it isn't. rasetsu already explained this, and Mister Agenda kudoed it. To my knowledge they're not YECs, yet they see the error in your method. This isn't some creationist trick. Your argument is faulty - it's an extrapolation fallacy coupled with an argument from ignorance fallacy.

Rasetsu explained incompletely and incorrectly.

You need to demonstrate that there is a limiting mechanism to the accumulation of change.

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Not to give short shrift to Rasetsu or Mister A, since I consider them both to be smart little bastards ( ) but the requisites for who I agree with don't boil down to "not a creationist." I can, and do, disagree with them on this issue, and after going back and rereading Rasetsu's post, I can tell you why.

And again, when smart people disagree on something, it's not a given.

The problem, broadly speaking, is a failure to take into account what defines a species when making her argument. What, exactly, is she using to determine what belongs in one species and what belongs in another? Population genetics demonstrably change, as does physiology, and if those aren't markers of speciation, what are?

Unless you're claiming that each new generation is a new species, such change does not necessarily indicate speciation. Further, the definition of macroevolution floated earlier specified change above the species level.

Is the proposition that genetics and physiology don't change, in spite of the evidence we're able to produce in a lab?

No.

Or is it that they don't change enough,

That's it - we haven't observed such change. You simply look at two populations which are similar but not exact duplicates and assume that one changed into the other.

and if so, where does one draw that line, given the huge variances we get in, say, dog breeds over a relatively short period of selective breeding within recorded human history?

That's an interesting point that I'll get into if anyone takes up the 29+ banner and we make it all the way to alleged fossil evidence. If all dogs are one species, then shouldn't we require that fossils with less difference than that known in dogs to be classified as the same species?

Or the observed instances of speciation that we've produced in a lab? By all accounts, our ability to observe both speciation and vastly different physiologies is fairly comprehensive, so what is this definition of species we're using that ignores both of those in order to make macro-evolution some distant thing?

We never agreed that speciation was equivalent to macroevolution, and in fact have had a definition of macroevolution that specified change above the species level.

As to this idea that we're assuming that these mutations will continue in a single direction... first of all, no we're not, as I've acknowledged multiple times that they don't always go in the same direction, but this faux confusion as to where we'd even get the idea that they would is baffling:

Uh, Sparky, we got that idea from your analogy: "the logical view is that small, demonstrable changes will build up, just as it's logical to consider that if I walk solidly in one direction without interruption, I will eventually have walked a mile."

So, the changes occur, and we know it's possible for them to occur and continue to intensify in line with the predictive power of natural selection, and we also know that by any genetic or cladistic definition this would eventually vary an organism out of one species classification and therefore into another... maybe it is just an inference based on observable evidence, but that's kind of what science is.

Inference based on observation isn't scientific evidence. Inference can give ideas for objectively testable, risky, falsifiable predictions. Those predictions are scientific evidence. Try reading the TO bit on scientific evidence.

Would you quit it with this "were you there?" crap?

No.

And what defines taxonomic classifications if not genetic and morphological differences?

Addressed above. It's a matter of extent.

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There is no such thing as "change above the species level".