Pigeons and Dogs: Micro or Macro evolution?

Limits exist. Great. Knowing that oceans exist doesn't prove that there's one between New York and St. Louis.You need to specifically prove that there's a specific limit right where you say it is. Now, we've observed lots of mutation. We've never observed any limit that would prevent speciation or evolution.We're looking where you say the limit should be, and we can't find it. What more evidence do you think we need to conclude that it isn't there?A hand-waving metaphor isn't going to cut it. The existence of limits in biology, as a general principle, is insufficient to prove the existence of a limit right where you'd like it to be. (And I know you'd so love there to be a limit, I just know you would, but wishing doesn't make it so...)

What way do you think the ToE requires mutations to accumulate? In what way is that different, in your belief, than the way we observe mutations accumulate? A great thing. There's a bazillion studies about how sexual reproduction is great for populations. And consider the example of genetic programmers. One thing every evolutionary algorhythm models is sexual recombination. Why would that be if it wasn't evolutionarily advantageous?

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Genetics. 2000 Dec;156(4):1913-31. Related Articles, Links

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The population genetics of the origin and divergence of the Drosophila simulans complex species.

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Kliman RM, Andolfatto P, Coyne JA, Depaulis F, Kreitman M, Berry AJ, McCarter J, Wakeley J, Hey J.

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Department of Genetics, Rutgers University, Piscataway, New Jersey 08854-8082, USA.

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The origins and divergence of Drosophila simulans and close relatives D. mauritiana and D. sechellia were examined using the patterns of DNA sequence variation found within and between species at 14 different genes. D. sechellia consistently revealed low levels of polymorphism, and genes from D. sechellia have accumulated mutations at a rate that is approximately 50% higher than the same genes from D. simulans. At synonymous sites, D. sechellia has experienced a significant excess of unpreferred codon substitutions. Together these observations suggest that D. sechellia has had a reduced effective population size for some time, and that it is accumulating slightly deleterious mutations as a result. D. simulans and D. mauritiana are both highly polymorphic and the two species share many polymorphisms, probably since the time of common ancestry. A simple isolation speciation model, with zero gene flow following incipient species separation, was fitted to both the simulans/mauritiana divergence and the simulans/sechellia divergence. In both cases the model fit the data quite well, and the analyses revealed little evidence of gene flow between the species. The exception is one gene copy at one locus in D. sechellia, which closely resembled other D. simulans sequences. The overall picture is of two allopatric speciation events that occurred quite near one another in time.

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PMID: 11102384 [PubMed - indexed for MEDLINE]

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Two species of flies, looks like. I'd tell you if they were two different kinds of flies if you'd only tell me what a kind is. (I notice you still haven't done that.) By keeping track of genomes. Mutation is the process of new genetic codes being inserted into a gene pool. If you detect a sequence that wasn't there before, that's a mutation. Why do I have to tell you this? I assumed it would be obvious. And yet, every population geneticist recognizes the great evolutionary advantage.

The only people who make this argument are people who've never created anything.You're a famous car designer. You're responsible for designing the suspension on the 2004 Honda Civic. You're really good at car suspensions. An expert, even.You're on the team now to design a submarine. (Don't ask me why.) Why would anything you know about Civic suspensions be applicable? In particular why would you throw in a useless Civic suspension into the submarine?If you came across a submarine with a useless Civic suspension, what would you conclude? That it was designed by the same guy who designed the Civic ("Intelligent" Design), or that the submarine was cobbled together by modifying Civic parts (evolution)?Common components doesn't support the same designer, because no one designer would be stupid enough to include useless parts just because they used them in another design. You show your ignorance not only of biology but of the design process in general.

What does that mean, exactly?Let's say that I present a hitherto-unseen quaduped mammal to you. By what method would you determine if it was in the dog "kind" or not?What makes some animals members of the dog "kind" and some others not? Some kind of Platonistic "dog" ideal? Or some kind of inherent dog-ness?

That's idiotic. As this is a discussion of macro and micro evolution, at issue here is what it would take for the offspring of a dog to not be a dog itself.Well, to determine that, we have to know what "dogness" is. We have to know how you determined that "a dog is a dog." We have to know why you're so comfortable asserting that no organism decended from the dog "kind" could ever be anything but a dog. Oh. So, a dog is a dog, unless it's a bear?Look, RB, if you're just going to play fast and loose with definitions of words, why even bother having the discussion? So, just so we're clear on your position, you believe that the K/T boundary represents the recent boundary of flood sediments? So you say, but then, you're the one who can't seem to tell the difference between a bear and a dog.

And you don't think an animal decended from dogs could be so different that we couldn't call it a dog?You don't think that would happen under any circumstances?

So, in other words, you don't know what dogs are, but you'd know one if you saw one?Can you imagine now why we don't bother to pay attention when Creationists open their mouths about species classification? they steadfastly refuse to get serious about it. How long is too long? How much can species change?Remember that your model predicts roughly (oh, what was it?) some million new species every year, to go from the 80,000 species on the Ark to the between 8 and 80 billion species there are today. That's quite a bit of species change. And you think dog to kangaroo (or, more acurately, mammal ancestor to both dog and kangaroo) is too much change? Why? The line is vague because there is no line. There's no fundamental difference between macroevolutionary change and microevolutionary change. It's like trying to find the line between near and far.

That's not what we're talking about.We're talking about stupendous change indeed, for a few generations, and then little change at all. What stimulates this great change?

But what's the mechanism that causes the change? I mean, we've observed how the opening of new niches can cause rapid species change - that's the position of punctuated equilibrium - but the proposed rate of change you're describing is far, far more than punk eek can account for. So what's the additional mechanism? Of course it's been found. It's well-known that the mechanism of speciation is simply reprouctive isolation and the accumulation of mutations in the absence of gene flow. ?

And you think that this:is a better visual match than this?Do you maybe need to have your eyes checked?

To the contrary, we've observed countless instances of new, persistent species. Of course not, as that takes many, many generations - more generations, in fact, that we've had the Theory of Evolution.But there are many, many examples where we can trace divergent, adapted populations back to a single population of ancestors, like the cichlid fish of Lake Victoria:

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In the October 11th (1990) issue of Nature, Meyer et.al. present of paper aimed at establishing if the cichlid fish species of Lake Victoria (Africa) are monophyletic or polyphyletic. (If they all share a recent common ancestor in that lake or came from separate lineages that invaded the lake). In their paper they sequenced a 363 bp part of the cytochrome b gene and a 440 bp segment of mitochondrial DNA from what is called the control region. They sequenced these genes from several species of fish in the lake and a few species from relatively nearby lakes.

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What they found was the sequences in the Lake Victoria species of fish were all very similar, but they were different from the sequences of fish in nearby lakes. All the sequences are listed in the paper.

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They came to the conclusion that this indicated the cichlid species of Lake Victoria all derive from a recent common ancestor in the lake. They estimate the time of divergence at about 200,000 years ago based on a model that assumes mutations are relatively constant over time. (The lake, incidentally, had been independently dated to be 250,000 - 275,000 years old)

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Why bother with your ridiculous, ad hoc, unknown magic mechanism when we have two mechanisms we already know about - natural selection and random mutation - that are more than adequate?This message has been edited by crashfrog, 09-25-2004 02:29 PM

As is the sameness of humans and apes. Personally, I choose to remain clothed when observing apes and humans, but that's just me.At any rate, if you're regularly confusing bears and dogs, I would reccommend putting your clothes back on, or at least your glasses.

That must be why they call you "lefty".

What are you talking about? Natural selection and random mutation have been observed, over and over again. Of course they've been observed. No, it's observation. We've observed these mechanisms and their effects, time and time again.