Posted on 12/21/2004 8:45:42 AM PST by PatrickHenry
The wide range of variety in domesticated dogs — from the petite Chihuahua to the monstrous mastiff — has powered a new view of what drives evolution.
Scientists have long known that the evolutionary changes that alter a species' appearance or create new species frequently occur in rapid bursts. One widely accepted theory holds that any evolutionary change results from a random switch of a single genetic unit within DNA.
These single-point mutations occur in about 1 out of every 100 million DNA sites each generation. This frequency is too low to cause rapid evolutionary change, assert John W. Fondon and Harold R. Garner, biochemists at the University of Texas Southwestern Medical Center at Dallas.
While examining human-genome data, Fondon found that small segments of repeated DNA sequences, called tandem repeat sequences, are frequently present in genes that control how an animal develops into its final appearance. Unlike single-point mutations, tandem repeat mutations occur when a cell's machinery for copying DNA makes a mistake and inserts a different number of sequence copies.
Such mistakes, which happen 100,000 times as often as single-point mutations, could alter an organism's appearance or function for successive generations.
"I was stunned by what I found," says Fondon. "It occurred to me that this might be a nifty way for [organisms] to evolve very rapidly."
To evaluate this hypothesis, Fondon and Garner looked for tandem repeat sequences in 92 breeds of domesticated dogs. For example, they examined a gene that determines nose length. They found that the number of times a particular sequence is repeated correlates strongly with whether a breed has a short or long muzzle.
Many researchers explain dog-breed diversity as the emergence of hidden traits in the genome. However, says Fondon, a more likely scenario is that genetic mutations occur in dogs at a high rate.
By comparing skulls of dogs over decades, Fondon and Garner found significant and swift changes in some breeds' appearances. For example, between the 1930s and today, purebred bull terriers developed longer, more down-turned noses.
Moreover, the researchers found more variation in tandem-sequence repeat lengths among dogs than they found in the DNA of wolves and coyotes.
These results suggest that dogs have experienced significantly higher rates of tandem repeat mutations than the related species have, says Fondon. Because tandem-repeat sequences litter the genes that control the developmental plan in many species, Fondon suggests that mutations in these regions could have a strong bearing on evolution.
"As a new finding about the biology and genetics of dogs, I'm all for it. But in terms of applying this to [evolution in general], I think there's a question mark," says Sean Carroll, an evolutionary geneticist at the University of Wisconsin–Madison.
Carroll notes that because dog owners have coddled their companions over the centuries, mutations that would have killed wild animals may have persisted in the gene pool of domestic dogs. Because domestication diverges from a standard model of evolution, he says, further experiments are necessary to add weight to Fondon and Garner's theory.
When I speak of spontanaity I speak of animals or plants popping into existance from nothingness. What you are talking about are pre-existing materials organizing into lifeforms these are two quite different ideas.
The next time a new species appears miraculously in your living room give me a call. I know new species can form, just not from a vacuum.
In your version of the universe in which God has ultimate creative power, we could wake up tomorrow morning and the moon could be covered with a rain forest inhabited by pygmys and leopards.
In my version of the universe this is an impossibility in such a short period of time, and would require eons for the moon to develop an atmosphere, water and other requirements for carbon based lifeforms as we know them.
Which version of reality do you live in?
Thanks and understood. You are, of course, correct in that it is not practical to breed tiny dogs and giant dogs, and that they cannot manage it on their own for obvious physiological reasons.
Nevertheless, my point was that the many breeds of Canis lupus familiaris, the domestic dog, are actually subspecies. Further, I believe that the basic point of the article's author is correct -- that the wide range of different dog subspecies can lead to a better understanding of how species evolve.
I'm suggesting if God spontaneously created plants and animals on this planet as seen in Genesis it would not be unexpected to wake up in the morning to a moon full of life.
Obviously sex is needed for the reproduction of all life, and one organism comes from its parent organism. Sex is the driver of evolution. If you want to think of the first organisms on the planet you might want to think about how chemistry mimics/emulates sexual procreation.
I guess I'm a little confused as to how you think life, insects, plants, animals etc. came to being on this planet.
:-} I don't "throw down dares". And I am simply a blue collar Luddite who knows what little about Quantum Theory that I do from reading about it on the internet.
Clearly you are asking him to explain something that you yourself do not understand.
Isn't that the general way of acquiring knowledge or are the really smart folks like you born with omniscience?
"And yet mass and energy were created in violation of the Conservation Laws" Did I say that? Nope.
You don't have to say it, it is implied by the BBT. Evidently you are unaware of that.
Since t=0 is an unobservable event, neither you nor I can say for certain what occurred before.
That would be correct.
Indeed BBT does not and can not say what came before. It could very well of been another universe that collapsed.
Doesn't matter a wit, you simply move the creation event back in time. That should be obvious to a man of your obvious scientific capabilities.
That does not however prove the existence of a Biblical God. By arguing such, you are simply proving the possible existence of a Deistic definition of God, not a Christian one.
Yeah, so what? I'm arguing that a creation event, of necessity, requires a creator. I believe in the big C Creator who sent Jesus Christ to save souls. What you believe is up to you.
"The probability that I brought Quantum Theory into the debate is null" I never said you did, but you dared the other guy to go there, so I went.
Now you're dissembling, thats exactly what you said. It was false.
"Does God consult with you often on the mechanisms he uses?" No, but you didn't answer the question. You simply appealed to authority. A rather weak argumentative tactic
You got the answer you deserved, such is life.
LOL, you're argument ain't wiht me pal its with the scientists and cosmologists who endorse the BBT. The BBT requires that the Laws of Physics were violated at t=0+. Like I said aabove, you don't have to subscribe to the BBT but if you do try to make an honest assessment of it. And BTW the BBT just doesn't violate the Laws of Conservation, it violates the 2nd Law of Thermodynamics and the Law of Angular Momentum. A truly momentous occasion.
Did you think it was from the Onion at first? :-}
Says that while, in very conjectural theory, the universe *might* be a creation.... it also points out that the "creator" might well be no more than some government science project.
Not the way I read it. The way I read it the scientist in question posits that it is a creation event but that it was no big deal. Sorta like your home chemistry kit and your magic wand and away we go.
For *real* philosophical fun, imagine 400 years from now, a group of physicists using a ringworld-sized supercollider create a universe. That universe being the one they inhabit. Thus they are their own creators. No beginning, no ending. Whoopee.
Sounds like faith healing. To each his own.
Other lines in quantum mechanical thinking about cosmogenesis posit that "pocket universes" are formed naturally due to the space-time stresses caused by black holes. And that each time this happens, the laws and constants are changed ("mutated") very slightly. This would lead to the evolution of universes that have physical principles most ameniable to the creation of large numbers of massive black holes. And since those principles are co-incidentally also good for the evolution of our form of life...
Right, but we're back where we started from. Where did the matter in the black holes come from?
Interesting conjectures, but at this time basically jsut conjectures. They do, however, have math behind them, that runs waaaaaaay over most peoples heads.
Conjecture is a very generous way of describing that article.
> Did you think it was from the Onion at first?
No. I saw it, and others like it, when it first came out.
> Where did the matter in the black holes come from?
Sneezed out the nose of the Great Green Arkleseizure?
> it requires that at some point life spontaneously erupted.
Again... scientists have assembled viable virii from simpler chemicals. The scientists didn't use magic or spells or mysterious incantations to bring these thigns to life; they simply put them together. Life, then, is simply a matter of being a sufficiently complex chemical structure. Nothing mystical about it.
Thats odd, thats the same answer that cosmologists offer for conditions at t=0. You guys all train at the same public school?
It's not a fundamentally different answer than "God did it." Both answers are BS.
I can do nasty BamBam. You sure you want to go that route?
Darwin himself warned strongly against thinking that evolution would operate normally within the constraints of society; why did no one listen?
Go ahead, with a little luck a mutation will occur.
I said nasty, not "the nasty". :-}
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.