Skip to comments.Kibble for Thought: Dog diversity prompts new evolution theory
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 WisconsinMadison.
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.
Well I for one am a little dog hating, creationist Rebel. Anyone got a problem with that?
The existence of cats disproves the possibility of natural selection.
There's lots of them neo-confeds who think Abe Lincoln was a son of a bitch -- so I guess we've got that connection, too!
Different dog types are not different species. They are different RACES within the species. Two of any type dog mated together produces viable offspring that can reproduce. This is even applicable to wolves and dogs. I have read that the DNA of a wolf and chihuahua are virtually identical, proving that all dogs are really domesticated wolves.......
Pocking and hoping to shore up the inevitable.
Another failed theory which adds nothing. Mutation isn't evolution, since no improvements are seen. And they can't prove the diversity doesn't already exist in the dog gene's.
Bless your heart ... you have such a sense of humor ...
LOL. It is a known fact that Sherman tortured cute little puppies who had rapidly evolved long noses on his March thru Georgia. There. Something for everyone.
I have read that the DNA of a man and a monkey are virtually identical, proving that all men are really ...
> Mutation isn't evolution, since no improvements are seen.
Aren't you cute! Yes, I'm sure that wolves are just as good at going undergound into critter-tunnels as Dachshunds, and that bulldogs can track smells as well as bloodhounds. Yes, there are no advantages from one mutation to another...
Humans feed and take care of dogs.
The dog thinks the human is a god.
Humans feed and take care of cats.
The cat thinks ITSELF is a god.
Monkeys and humans cannot mate and produce viable offspring that can reproduce themselves.....
Been talking to my wife?
Dogs have Masters
Cats have Staff
I believe that they are selectively breeding humans with the servitude gene.
Have you seen Helen Thomas?
The farm is an adequate laboratory as any--at least you don't have some Piled High and Deeper grubbing for a grant...
I find the stories of the breeding of domestic sheep and goats to be far more compelling an argument against speiciation than even the breed-variety in dogs, because this breeding has been going on for far longer (thousands of years, a generation a year), with far wider geographical isolation, and with more interesting results. Due to an interest in textiles and small-scale farming, I'm familiar with a wide variety of breeds of sheep and goats.
The Merino sheep, bred for wool and only incidentally for meat, has a skin with deep folds--there's a lot more skin on a Merino than on a meat sheep, which makes for many more follicles and much more wool! But the Merino is hard to shear--you risk nicking all that skin. Meat sheep are bred for twinning, with all the complications and benefits that causes the shepherd. Most modern domesticated sheep breeds can no longer shed their wool. If they are not shorn regularly, they will die from the weight and burden of the long wool.
There is a breed of goat, the Nubian, which has large ears to act as a kind of air-conditioner in hot climes (India). It is also the breed with the highest butterfat content in its milk. There is a goat bred for the alpine that has no ears at all!--which means those ears can't freeze off.. The little tempermental Angora goat, looking for all the world like a poodle and very much a diva, has long silky white curls which provide our mohair. <"Mom, what's a 'mo'?)
Goats bred in India, goats bred in the Alps, sheep in Iceland and sheep in the Holy Land. All the same goat--all the same sheep. No new species.
The mutated flu viruses would beg to differ.
The only potentially truthful line in the article.
"Many researchers explain dog-breed diversity as the emergence of hidden traits in the genome."
The rest is a waste of time and money. Even as a layperson, I can tell these guys are out of their league.
Right. Somewhere, eons ago, the chain split, monkeys going one way, man going another.
AND an opus...
Bless you! ;-)
The Age of Savagery ended and the Barbarian Age began when Man domesticated Dog.
The Barbarian Age ended and Civilization began when Cat domesticated Man.
Also, there is no genetic problem with any dog breed interbreeding with another, aside from problems caused by differences in size.
Bottom line is, there has been no "evolution" of dog breeds.
Existing genetic traits have merely been selected for and amplified by dog breeders.
Is this from personal experience or something you read?
A "species" is defined as a a group that can naturally breed and produce viable offspring (that can itself breed).
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.
And no, artificial insemination does not count.
If so, lions and tigers would be the same specifies (the resulting offspring is called a Liger, which do exist, albeit they are generally sterile like a mule, which is itself an inter-species cross ).
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).
So many breeds have been "created" by man for specific traits such as size, coat, skills, etc., I don't think this research means much. Additionally, the cultivation of certain traits also (inadvertently) has led to other problems within breeds, such as susceptibility to certain afflictions, etc.
These things take time. We haven't been dealing with dogs for very long. Give it a few thousand more dog generations. Speciation is virtually inevitable.
That's not entirely correct as evolution is simply the change in the frequency of alleles from one generation to the next. Selective breeding of dogs is a prime example of this. If your talking in terms of speciation then you are correct. No speciation has occurred.
You remain hilarious. Every time you post on this topic, I get an image of a monkey with its eyes clamped shut and its hands covering its ears, a grimace of extreme frustration on its face...
One more bit of evidence for evolution to add to the mountain. One more bit of serious annoyance to the Poofists. Gotta love it!
>Even as a layperson, I can tell these guys are out of their league.
And you can tell that... how? Because they reached a conclusion you don't like?
As I've noted several times on threads such as these, the best argument in favor of Intelligent Design (as a general principle) is that we humans have practiced it for thousands of years. Yours are among the best specific examples I've seen.
It doesn't? Gee, a lot of horse farms will be interested to know that their horses ain't horses.
Since you credit the Chinese story of inter-primate breeding, should I believe you when you define two breeds of dogs as two species?
Stop that, CG! I almost lost my lunch!
Right, the one with the fish playing baseball...floating there with bat in fin, looking out at the ball that is on dry land.
There was no such fly, it was a lie...perhaps he'll die...
But it did get me thinking about the humble fruit fly and all that creature has contributed to the study of genetics without happening to "evolve" in the laboratory! The life cycle of a fruit fly is very brief, and scientists have been monkeying with them for *hundreds* of years in labs all over the world. You'd think, wouldn't you--that there'd be a new one by now, just by accident?
I don't happen to hold with ID--though it makes better sense than evolution. It's all a matter of time--and who controls the wheels of time.
Introducing the Stretch & Squish Theory of Evolution
How do you stretch an arm into a wing, or a fin into a leg? This sounds like the silly putty theory of evolution. An intelligent kid can purposefully make things out of silly putty, but the putty by itself is silly and has no goal in mind. Put the silly putty into a random machine of moving parts and chaos results.
Other problems quickly evolve from this theory. What if the top of the dogs snout gets stretched by a tandem repeat mutation, but the bottom jaw does not? The dog cant eat. What if the mutated dog can eat, but cannot find a mate with the same mutation? And dont these guys know that dog breeding is not evolution, but intelligent design?
For these and other reasons, this Silly Putty theory of evolution gets Stupid Evolution Quote of the Week: their final sentence in the paper makes tandem repeats responsible for all the beauty and variety of living things:
How broadly this mode of evolutionary change is exploited [sic] in nature remains to be seen, but if the prevalence of repetitive elements within genes is any indicator, then mammals, insects, plants, and other genomes throughout the natural world may use this mechanism [sic] to achieve evolutionary agility.
Evolutionary agility now there is an equivocation for the record books. How did a lizard learn to fly? By evolutionary agility. How did an ape learn to build spacecraft? By evolutionary agility. How did a dog learn to become a whale and dive deep into the ocean, navigating by sonar? By evolutionary agility. What an agile concept.
Papers like this diminish the prestige of the National Academy of Sciences. Peer review is supposed to prevent dumb ideas from getting published. If it were not for the desperation of the Darwin Party to keep sending new ideas up the flagpole to see if anyone salutes, they would have been forced to admit defeat long ago. This entrys only value is in pointing out that the old neo-Darwinian theory of natural selection, acting on point mutations, is inadequate to account for the rapid change found in the fossil record. That is an admission that supports creation, not evolution.
Oh, dat is sweet. Flop-eared bunny.
"In vitro" is different from "in vivo" from "in the wild." (Seems the Romans were very civilized, no Latin for "in the wild.")