Free Republic
Browse · Search
News/Activism
Topics · Post Article

Skip to comments.

Kibble for Thought: Dog diversity prompts new evolution theory
Science News ^ | 18 December 2004 | Christen Brownlee

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.


TOPICS: Culture/Society; Miscellaneous; Philosophy
KEYWORDS: agriculture; animalhusbandry; crevolist; darwin; dietandcuisine; dog; dogs; domestication; evolution; godsgravesglyphs; helixmakemineadouble; huntergatherers; morphology
Navigation: use the links below to view more comments.
first previous 1-20 ... 61-8081-100101-120 ... 261-267 next last
To: MeanWestTexan
In fact, HUMANS and CHIMPS can be bred together via artificial insemination. The Chinese did this, impregnating female chimps with human sperm. Fortunately, the resulting creature was destroyed before term (or so the Chinese claim).

Do you have a source for this?

81 posted on 12/21/2004 9:53:13 AM PST by Modernman (Beer is proof that God loves us and wants us to be happy. --Benjamin Franklin)
[ Post Reply | Private Reply | To 33 | View Replies]

To: MeanWestTexan

I read the assertion in the link with some interest. I note that the terminology here is different from what I heard around the farm. But what is done with this non-sterile mule mentioned therin? Who's his baby?


82 posted on 12/21/2004 9:53:32 AM PST by Mamzelle (He's scared of me...! Honest, I won't hurt him!)
[ Post Reply | Private Reply | To 75 | View Replies]

To: Rodney King
I had 2 Rhodesian, same parents but from different litters. Two of the best dogs I have ever had out of the dozens and dozens I have owned in my life. The male was magnificent, tall, husky but he had no ridge. Odie weighted 120 at his prime. Hazel was smaller but she was the brains of the outfit. Their ashes are on my bookshelf in urns. Hazel caught a new yardman in the back yard, put her mouth around the back of the mans thigh (lightly) and cut her eyes to me for further instruction. She would have taken him down if I had told her to.

I have Jack Russel Terriers now, the kind you hate but they are wonderful.

I will have a RR again someday, where did you get yours?
83 posted on 12/21/2004 9:53:59 AM PST by Ditter
[ Post Reply | Private Reply | To 58 | View Replies]

To: MeanWestTexan

There's a lot of Angora goats in West Texas...I seem to remember Sam Donaldson getting a nice tax break from the little horned poodles.


84 posted on 12/21/2004 9:54:50 AM PST by Mamzelle (He's scared of me...! Honest, I won't hurt him!)
[ Post Reply | Private Reply | To 80 | View Replies]

To: Weimdog

My lab would play with them all unless I tossed them in the air and shot them over the water. Then she'd wait for me to signal and go get them.


85 posted on 12/21/2004 9:55:47 AM PST by Conspiracy Guy (Boycott Boycotts Warrior. If you aint buying call me!)
[ Post Reply | Private Reply | To 76 | View Replies]

To: Mamzelle

Don't know. Never saw it happen myself.

Ironically, I learned that mules are not always sterile in Asimov's Foundation series --- had to go look it up, because, like you, I thought mules were always sterile.


86 posted on 12/21/2004 9:56:00 AM PST by MeanWestTexan
[ Post Reply | Private Reply | To 82 | View Replies]

To: Mamzelle

Angora = Emu, 10 years later, IMHO.

Not that I don't raise them and sell them to people with "ranches" outside of Houston, mind you.


87 posted on 12/21/2004 9:57:17 AM PST by MeanWestTexan
[ Post Reply | Private Reply | To 84 | View Replies]

To: PatrickHenry
For example, between the 1930s and today, purebred bull terriers developed longer, more down-turned noses.

I don't suppose that could be due to breeding choices of the owners???

88 posted on 12/21/2004 9:58:05 AM PST by trebb ("I am the way... no one comes to the Father, but by me..." - Jesus in John 14:6 (RSV))
[ Post Reply | Private Reply | To 1 | View Replies]

To: forsnax5

There's one not quite this bad on a route I travel--being kept as a pet, I fear, with no knowledge that they're going to have to get it shorn! I've been wondering whether to play the busybody and give them a call. Then they might expect me to find them a barber. Did you know that some wool producers now have a hormone they can inject into the sheep which will cause all the hair to fall off in a convenient fleece? I thought it would revolutionize wool production, but it is not widely used. I suspect it may harm the meat...?


89 posted on 12/21/2004 9:58:09 AM PST by Mamzelle (He's scared of me...! Honest, I won't hurt him!)
[ Post Reply | Private Reply | To 79 | View Replies]

To: weenie
Monkeys and humans cannot mate and produce viable offspring that can reproduce themselves..... Is this from personal experience or something you read?

Something my Biology Professor said years ago and Michael Moore does not count......

90 posted on 12/21/2004 9:59:32 AM PST by Red Badger (If the Red States are JESUSLAND, then the Blue States are SATANLAND......)
[ Post Reply | Private Reply | To 32 | View Replies]

To: PatrickHenry

I believe, though, that they have studied populations of feral dogs, and their diversity.

Mutts do, after a few generations, tend to lose the non-dominant breed specific traits, and all tend towards the characteristics that match coyote/wolf traits.

So I would be hard pressed to say that specific breeds is a tendency in evolution. Those breeds were selectively bred for the desired trait. Evolution tends to support a more general purpose mutt.


91 posted on 12/21/2004 9:59:32 AM PST by djf
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry

Thanks for the ping!


92 posted on 12/21/2004 10:01:44 AM PST by Alamo-Girl
[ Post Reply | Private Reply | To 2 | View Replies]

To: MeanWestTexan
Mastiffs and Chijuaja(sp?) cannot naturally breed. Ergo, although they had a common ancestor just a few hundred years ago, they no are no longer the same species.

The only limitation here is physical, same as with some humans, Pygmies and Zulus, comes to mind, but no one would claim that they both are not the same species. A dog in heat is a dog in heat, regardless of size, shape or demeanor. The attempt would be made by them in spite of size difference. And if successful would produce viable reproductive offspring....

93 posted on 12/21/2004 10:03:37 AM PST by Red Badger (If the Red States are JESUSLAND, then the Blue States are SATANLAND......)
[ Post Reply | Private Reply | To 33 | View Replies]

To: Red Badger
Michael Moore does not count......

Heh, heh...

If I am not mistaken, it was Cokie Roberts who said recently that Michael Moore hurt the democratic ticket (paraphrasing, probably erroneously)..."just by his physical appearance."

94 posted on 12/21/2004 10:07:12 AM PST by weenie (Islam is as "dangerous in a man as hydrophobia in a dog." -- Churchill)
[ Post Reply | Private Reply | To 90 | View Replies]

To: djf
general purpose mutt.

I have two GP Mutts and two pure breds, Retriever and Chihuahua. My GP mutts are smarter and easier to train. The pure bred Retriever just wants to play fetch, which is what he was created for. The Chihuahua just wants to be petted and lay around all day, for the same reason....

95 posted on 12/21/2004 10:07:56 AM PST by Red Badger (If the Red States are JESUSLAND, then the Blue States are SATANLAND......)
[ Post Reply | Private Reply | To 91 | View Replies]

To: Modernman

Not handy, but you can Google "humanzee" or various combinations of "hybrid" or "chimera" and come up with it pretty easily.

Also, nutcase biologist Newman (?) filed a patent on human-chimp cross in the US, I think.


96 posted on 12/21/2004 10:11:23 AM PST by MeanWestTexan
[ Post Reply | Private Reply | To 81 | View Replies]

To: MeanWestTexan
Thanks.

Interesting, but terribly disturbing.

97 posted on 12/21/2004 10:12:06 AM PST by Modernman (Beer is proof that God loves us and wants us to be happy. --Benjamin Franklin)
[ Post Reply | Private Reply | To 96 | View Replies]

To: Mamzelle

> What's a Poofist?

A more accurate description of the fariy-tale of Creationism. God said "Ummm..." and all the critters of the world went "poof" and there they were. The fossils went "poof" and there they were, already made, and made old, showign clearly evidence of evolution (God apparently playign a little prank). The stars and galaxies went "poof" and there they were, billions of lightyears apart, but wioth the light already travelled between.

Yes, it's silly... but that's Poofism for you.


98 posted on 12/21/2004 10:12:55 AM PST by orionblamblam
[ Post Reply | Private Reply | To 62 | View Replies]

To: bondserv

> Darwinism really has taken on the mentality of the Left.

Somehow, you misspelled "Creationism" as "Darwinism."


99 posted on 12/21/2004 10:14:21 AM PST by orionblamblam
[ Post Reply | Private Reply | To 56 | View Replies]

To: Ditter
I had 2 Rhodesian, same parents but from different litters. Two of the best dogs I have ever had out of the dozens and dozens I have owned in my life. The male was magnificent, tall, husky but he had no ridge. Odie weighted 120 at his prime. Hazel was smaller but she was the brains of the outfit. Their ashes are on my bookshelf in urns. Hazel caught a new yardman in the back yard, put her mouth around the back of the mans thigh (lightly) and cut her eyes to me for further instruction. She would have taken him down if I had told her to. I have Jack Russel Terriers now, the kind you hate but they are wonderful. I will have a RR again someday, where did you get yours?

My girl ridgeback is a ridgeless as well, she was the sweetest dog of the litter, and without the ridge she was a good 700 dollars than the good dogs with ridges. There is a great breeder of champion ridgebacks 10 minutes away from me in OK, that is where I got her. If you are ever in the market for a ridgeback again, I would be glad to put you in touch with the breeder.

100 posted on 12/21/2004 10:15:51 AM PST by Rodney King (No, we can't all just get along.)
[ Post Reply | Private Reply | To 83 | View Replies]


Navigation: use the links below to view more comments.
first previous 1-20 ... 61-8081-100101-120 ... 261-267 next last

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.

Free Republic
Browse · Search
News/Activism
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson