David Cohen has said here (and I paraphrase) that mutations happen and will persist if they do not interfere with survivability. Sounds reasonable enough, but that rule allows for the possibility that some mutations might actually enhance survivability.

It would be a huge leap, of course, to conclude that all species have been so created.

The Grant's research has shown finch variation (about 15% change in some beak lengths) over about 25 years due to climatic changes, but well within the range of normal variation and never enough to constitute a new species.

Heh heh, you guys are a hoot.

Can't wait for the next story:

"Nobody takes that story about Archimedes in his bath seriously anymore. Everyone knows he just jumped out because the water was too hot. The law of buoyancy has no way been proven."

Every one a coconut!

I'd like to see a mechanism for the changes in chromosome structure between species. It's one thing to say that an A, T, C, or G nucleotide can mutate to another one through copying errors; it's something else to say how 32 chromosomes can mutate to 37.

PJ: That's one of my main questions, too. Breeding between creatures with different number of chromosomes can happen and has been observed. That it would result in a stable breeding population, and that it could happen as often as it would have had to happen to explain the variation we observe, is incredibly unlikely, but then there's that whole billions of years thing, so it can't be ruled out.

PJ:

I think (not sure, though) the terms are haploidism and diploidism.

It happens in plants fairly frequently, in animals less often.

And we shouldn't forget the role viruses play as natural genetic engineers.

Jeff - I don't pretend to any sort of expertise in evolutionary genetics, but I suspect if definite mechanisms had been worked out, I would have heard of it. It seems like the sort of thing that would get trumpeted in the press.

My suspicion just from superficial skims is that polyploidism is a description of phenomena and regularities of structure, not a molecular mechanism describing an evolutionary process.

No doubt viruses may be key, but until a mechanism is understood viruses playing the role of genetic engineers is as consistent with Intelligent Design as with evolutionary theory.

Giant tortoises? I don't follow any of this too closely but I thought I've read that animals got smaller when isolated on islands.Where there some truly GIANT tortoises at one time?

It's tortoises all the way down...

Rick, what you read was one of multitudinous silly statements about evolution.

I've pointed out here before, more than once, that islands tend to develop extremes, but in each direction.

There are other island-mediated types or evolution that are unidirectional. On islands without large browsers, immigrant plants with thorns tend to lose them, and quickly, too; but I know of no examples where a thornless plant evolved thorns on a browserless island.

pj is wrong about polyploidy not being an evolutionary process.

Since chromosomes can be observed to break up and recombine in unusual ways -- not necessarily lethal -- the objection is another creationist delusion.

Harry - I didn't say it isn't, I just said I haven't seen any mechanisms either described in detail or observed empirically.

My intuition is that it will be difficult to find a mechanism that is consistent with the "random mutation followed by natural selection of the resulting organisms" idea. Any mechanism for restructuring the whole genome faces (a) a combinatorial explosion of possibilities, which will probably have a ratio of incapable of supporting life to capable of 10^30 to 1; and (b) the empirical fact that wholesale restructurings of the genome don't seem to occur spontaneously in nature with any observable frequency; leading to the conclusion (c) that a process of uncontrolled random genome mutations followed by selection at the organism level is far too slow to be consistent with historical evolution. So any evolutionary process that restructures the genome will have to be "guided" in some way by a feedback loop that causes beneficial restructurings to have a much higher probability than damaging restructurings. And until we know what this "guiding" feedback process is, we can't say that there's been any scientific refutation of Intelligent Design.

Harry:

Yet no matter how isolated they can all still breed.

pj;

There are number of known human genetic diseases which are caused by duplicated chromosomes, so adding extra chromosomes does in fact happen all the time. All you need then is time for one such modification to not be harmful and spread in an isolated population, both of which are easy if you're willing to wait millions of years.

For each one.

Pj, you admit you're not an expert. Read the experts. One I've been reading lately who is excellent is Professor P.Z. Myers of the U. of Minnesota-Morris, who has a blog, pharyngula.org.

You'd be surprised what some people know that you don't.

Harry - The reason I know so little is that I've never seen evidence that studying evolutionary science would yield a positive return on investment. I haven't yet heard anything to change that assessment. Since I know I don't know what they know, I'd be surprised if what they know surprised me.

AOG - I don't think that the genetic differences that distinguish genuses are as simple as a duplicate chromosome. The question is whether transitions between the actual genomes of genuses thought to be evolutionarily linked can be reproduced by realistic mechanisms. Answering that would require deeper knowledge than I think exists.

In short, I think evolutionary genetics is what Don Rumsfeld called a "known unknown". We know that we don't know. So how are contrary speculations to be settled? By science ... but there's no telling how long that may take. Wake me up when there's an answer.

Well, there's already an answer. The mechanism is the same as among the finches. The way it works is now understood down to molecular level. How much deeper do you think is needed? (Morris has a recent post on the golden nematode that even amateurs can appreciate; try it.)

Orrin's crack about Grant is, as he knows, out of context. The reason that only Peter Grant (and his wife) recognizess the differences is that they are subtle (half a millimeter difference in beak depth turned out to be the margin of death during the drought) and that selection pressure varies by season. The Grants had to wait for decades to encounter a drought serious enough to make their statistical calculations.

Nobody else but the Grants made the effort.

By comparison, the effort to apprehend the current state of evolution/development is slight.

But you'll have to shuck your naive inductionism, at least temporarily, to make even that effort worthwhile.

If I can make the effort to understand ID (I already have), you can make the effort to understand biology.

The same as how finches haven't evolved?

"The same as how finches haven't evolved?"

That the finches have evolved has been demonstrated; whether that evolution rises to the level of speciation is another question.

No speciation, no evolution.

"No speciation, no evolution."

That may well apply to evolution as a whole, but the finches are a perfectly servicable demonstration of microevolution and natural selection at work.

creeper:

Agreed. They're a perfect example of how little they can achieve.

So you agree that finches are a perfectly servicable demonstration of microevolution and natural selection at work.

Thank you.

creeper:

Yes, finches are the perfect example of what Nature can do on its own.

That's right, in a relatively small timespan, finches can adapt according to the principles of natural selection.

No limit has been established by critics to ascertain why there should be a natural limit to this.