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.
> If evidence points towards a creation event ...
Sure. But there is no such evidence at this time. Find a message in "pi" or the natural log of 2, or find a human hand in the stomache of a velociraptor skeleton, or find a trilobite swalloped by a carp and pierced with a fish hook,or find a T-Rex skeleton on the Moon.... *then* you'll have some evidence. Right now... you don't. Right now the best you have is a mystery of "where did it all come from." That is a mystery... not evidence.
When the river is rising, you just keep heading for the hills.
I'm contemplating sending you a bill for one laptop keyboard.
LOL
> I don't believe that just because you say so.
Good! Skepticism! Display similar skepticism in claims in ancient texts, and you'll be on your way.
> if someone doesn't fully understand the theory, how can he be so certain of its veracity?
Do you understand the tensor calculus required for a good understanding of the Theory of Relativity? No? Would you be willing to stand next to an H-Bomb, then? Do you understand the math behind quantum gravity? No? Then would you be comfortable standing under a suspended 16-ton weight?
Heck, I make rockets, and I don't have a deep understanding of the relevant combustion phenomena. I routinely cast urethane resin parts from silicone rubber molds built off of Bondo originals... all of which use chemical reactions I don't know squat about. Yet I am substantially certain that if you mix A and B together, you get a solid with reliable properties.
Similarly, one doesn't need to understand the complexities of mutations and continental drift and sediments turning into rocks to look at the fossil record and notice that critters change over time.
If I may use an analogy. Darwin is to Evolution what Newton was to gravity. Now Newton was pretty smart and his theory and equations work for most every day life. However, they fall apart at relativistic speeds. Now along comes the gravity equivalent of a creationist, who says that because Newton’s work doesn’t work at speeds approaching c that therefore the whole theory of gravity is wrong, and proves the existence of God. That is what ID and creationist proponents are putting out there. Taken out of the context of evolution, does the above sound logical at all? Gravity is still gravity. Now what evolution needs is its equivalent of Einstein to come along and revise and true up the theory so that it works in almost all cases. However, Newton’s stuff being simpler, and easier to understand is still taught in the schools. Same thing here, Darwin’s theory may not work in all cases, but overall it does work for everyday use. Just because you don’t understand relativity, doesn’t mean you can’t discuss laws of motion.
"[W]hen creationists say they believe microevolution occurs, what they really mean is that they believe variations within a kind of animal or plant occurs. Sometimes these variations can lead to a new species, and in some cases, even a new genus. But the variations have limitations. That limitation is within the genetic information of the organism. For instance, dogs can produce numerous varieties of dogs, but they will never produce a fundamentally different kind of animal, such as a cat (similar perhaps in shape and form, but an entirely different kind of animal). It’s just not within their genetic content. In my experience, evolutionists will quickly question exactly what a "kind" is. I’ll admit that it is partially true that creationists don’t have a definite definition of what a kind is, but this shouldn’t be cause for concern. Evolutionists don’t have a definite definition on what a species is either...."
To which of these postions do you adhere? And, as a matter of curiosity, if you the adhere to the notion that "kinds" represent the macro-evolutionary boundry, of what "kind" would you classify the spotted hyena?
I respectfully disagree that compatiability requires a disinterested God.
Going back to the cake analogy, the study of how the cake solidifies is not incorrect because the baker takes the cake out and puts icing onto it --- you just have two forces at work.
It is like how scientist recently showed that the Red Sea can naturally part --- certain wind conditions, tides, and all that. "No miracle!" some cry. "Heresy!" cry others.
Well, the miracle was not the parting, the miracle was parting just as Moses showed up with Pharoah on his tail, and then closing back up.
I am quite sure God put the wind, tides, etc, in motion a million years ago to get that one just right.
Same with evolution. He created just the exactly right conditions for things to be as he wanted.
It's very similar to a baker putting the micrograms of whatnot to get a souffle to rise just so.
Yes, God could intervene and bypass His rules of nature. But why? He made the rules. He knows how they work. Why should he not follow His own rules?
So to answer your quandry: "we would never know which species evolved purely from evolutionary mechanisms, and which were given a helping hand by the Creator"
This assumes God made a mistake in putting the Universe in motion.
ALL were given the exact helping hand by God --- be it by a timely asteroid killing dinosaurs just as those mamals got going, or by parting the Red Sea at the right time.
I do not presume that God would make a mistake. I presume He did it right and it is exactly as He desinged it.
I love weims. They are like skinny velvet Labs.
I'm ready, but it is not the end times. I get grandchildren first. It's in the contract.
Good summation of evidence for the Big Bang. No evidence whatsoever for a creator.
Sorry, you already agreed that a creation event implies a Creator. Be more careful in the future.
> you already agreed that a creation event implies a Creator
Yes, but there's no evidence of a "creation event." The fact that the universe is here is not evidence that it was created anymore than the fact that a rock may be aesthetically pleasing means that someone made it so.
The Big Bang is a creation event. Now you don't have to subscribe to the Big Bang Theory any more than you have to marry a rock but if you do I'd expect you to be honest that the BBT is a creation event and that you'd support the pebbles that issue from your marriage to the rock.
> Laymen have seen H-bombs go off and 16-ton weights crush things.
Just as laymen have seen the evidence of evolution.
> but we have never actually seen it occur
Incorrect. Do some research.
> the arguments for Creationism.
There are no valid arguements *for* Creationism. Creationism is the John Kerry of the "origin of species" world; nobody is "for" it, they are just against the GWB of evolution.
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