Posted on 05/31/2005 12:03:06 PM PDT by PatrickHenry
In a stunning example of evolution at work, scientists have now found that changes in a single gene can produce major changes in the skeletal armor of fish living in the wild.
The surprising results, announced in the March 25, 2005, issue of journal Science, bring new data to long-standing debates about how evolution occurs in natural habitats.
“Our motivation is to try to understand how new animal types evolve in nature,” said molecular geneticist David M. Kingsley, a Howard Hughes Medical Institute investigator at the Stanford University School of Medicine. “People have been interested in whether a few genes are involved, or whether changes in many different genes are required to produce major changes in wild populations.”
The answer, based on new research, is that evolution can occur quickly, with just a few genes changing slightly, allowing newcomers to adapt and populate new and different environments.
In collaboration with zoologist Dolph Schluter, at the University of British Columbia, Vancouver, Canada, and Rick Myers and colleagues at Stanford, Kingsley and graduate student Pamela F. Colosimo focused on a well-studied little fish called the stickleback. The fish — with three bony spines poking up from their backs — live both in the seas and in coastal fresh water habitats all around the northern hemisphere.
Sticklebacks are enormously varied, so much so that in the 19th century naturalists had counted about 50 different species. But since then, biologists have realized most populations are recent descendants of marine sticklebacks. Marine fish colonized new freshwater lakes and streams when the last ice age ended 10,000 to 15,000 years ago. Then they evolved along separate paths, each adapting to the unique environments created by large scale climate change.
“There are really dramatic morphological and physiological adaptations” to the new environments, Kingsley said.
For example, “sticklebacks vary in size and color, reproductive behavior, in skeletal morphology, in jaws and teeth, in the ability to tolerate salt and different temperatures at different latitudes,” he said.
Kingsley, Schluter and their co-workers picked one trait — the fish's armor plating — on which to focus intense research, using the armor as a marker to see how evolution occurred. Sticklebacks that still live in the oceans are virtually covered, from head to tail, with bony plates that offer protection. In contrast, some freshwater sticklebacks have evolved to have almost no body armor.
“It's rather like a military decision, to be either heavily armored and slow, or to be lightly armored and fast,” Kingsley said. “Now, in countless lakes and streams around the world these low-armored types have evolved over and over again. It's one of the oldest and most characteristic differences between stickleback forms. It's a dramatic change: a row of 35 armor plates turning into a small handful of plates - or even no plates at all.”
Using genetic crosses between armored and unarmored fish from wild populations, the research team found that one gene is what makes the difference.
“Now, for the first time, we've been able to identify the actual gene that is controlling this trait,” the armor-plating on the stickleback, Kingsley said
The gene they identified is called Eda, originally named after a human genetic disorder associated with the ectodysplasin pathway, an important part of the embryonic development process. The human disorder, one of the earliest ones studied, is called ectodermal dysplasia.
“It's a famous old syndrome,” Kingsley said. “Charles Darwin talked about it. It's a simple Mendelian trait that controls formation of hair, teeth and sweat glands. Darwin talked about `the toothless men of Sind,' a pedigree (in India) that was striking because many of the men were missing their hair, had very few teeth, and couldn't sweat in hot weather. It's a very unusual constellation of symptoms, and is passed as a unit through families.”
Research had already shown that the Eda gene makes a protein, a signaling molecule called ectodermal dysplasin. This molecule is expressed in ectodermal tissue during development and instructs certain cells to form teeth, hair and sweat glands. It also seems to control the shape of - bones in the forehead and nose.
Now, Kingsley said, “it turns out that armor plate patterns in the fish are controlled by the same gene that creates this clinical disease in humans. And this finding is related to the old argument whether Nature can use the same genes and create other traits in other animals.”
Ordinarily, “you wouldn't look at that gene and say it's an obvious candidate for dramatically changing skeletal structures in wild animals that end up completely viable and healthy,' he said. "Eda gene mutations cause a disease in humans, but not in the fish. So this is the first time mutations have been found in this gene that are not associated with a clinical syndrome. Instead, they cause evolution of a new phenotype in natural populations.”
The research with the wild fish also shows that the same gene is used whenever the low armor trait evolves. “We used sequencing studies to compare the molecular basis of this trait across the northern hemisphere,” said Kingsley. “It doesn't matter where we look, on the Pacific coast, the East coast, in Iceland, everywhere. When these fish evolve this low-armored state they are using the same genetic mechanism. It's happening over and over again. It makes them more fit in all these different locations.”
Because this trait evolves so rapidly after ocean fish colonize new environments, he added, “we wondered whether the genetic variant (the mutant gene) that controls this trait might still exist in the ocean fish. So we collected large numbers of ocean fish with complete armor, and we found a very low level of this genetic variant in the marine population.”
So, he said, “the marine fish actually carry the genes for this alternative state, but at such a low level it is never seen;” all the ocean fish remain well-armored. “But they do have this silent gene that allows this alternative form to emerge if the fish colonize a new freshwater location.”
Also, comparing what happens to the ectodysplasin signaling molecule when its gene is mutated in humans, and in fish, shows a major difference. The human protein suffers "a huge amount of molecular lesions, including deletions, mutations, many types of lesions that would inactivate the protein," Kingsley said.
But in contrast, “in the fish we don't see any mutations that would clearly destroy the protein.” There are some very minor changes in many populations, but these changes do not affect key parts of the molecule. In addition, one population in Japan used the same gene to evolve low armor, but has no changes at all in the protein coding region. Instead, Kingsley said, “the mutations that we have found are, we think, in the (gene's) control regions, which turns the gene on and off on cue.” So it seems that evolution of the fish is based on how the Eda gene is used; how, when and where it is activated during embryonic growth.
Also, to be sure they're working with the correct gene, the research team used genetic engineering techniques to insert the armor-controlling gene into fish “that are normally missing their armor plates. And that puts the plates back on the sides of the fish,” Kingsley said.
“So, this is one of the first cases in vertebrates where it's been possible to track down the genetic mechanism that controls a dramatic change in skeletal pattern, a change that occurs naturally in the wild,” he noted.
“And it turns out that the mechanisms are surprisingly simple. Instead of killing the protein (with mutations), you merely adjust the way it is normally regulated. That allows you to make a major change in a particular body region - and produces a new type of body armor without otherwise harming the fish.”
We know evolution works because we have actually used it in everything from microbiology, to bacteriology, to computer science, to electrical engineering and many others I'm too lazy to look up.
And then what does it become?
Do the scientists know this?
Specific examples of Genetic Algorithms. Practical applications galore!
Another service of Darwin Central, the conspiracy that cares.
Where does the ToE state that a fish would or could ever turn into a fish?
So far all I see is someone who knows absolutely nothing about evolution refusing to jeopardize their tightly held belief system by actually reading up on it.
Lions, and tigers, and bears, oh my! (Just to bring Kansas back in to the picture.)
This is your brain on creationism!
Genetic Placemarker
I think this individual wandered too far down the yellow-brick road.
Onion was referring to your use of the argumentum ad ignoratiam you are using as the main basis of your argument. This last argument of yours is an example of the fallacy of equivocation.
Contrary to a number of anti-evolutionists, evolution is not based on metaphysical naturalism, nor on some twisted concept of methodological naturalism, but on a system of methods used by virtually all other science disciplines.
If you feel that this methodology should be used by other science but not by evolutionary scientists, could you explain why?
And silverfish are never produced from a cross of goldfish (regardless of Bryan's comments.)
Some have moved them to the kingdom level. Anyone claiming "a plant is a plant" has never worked with kudzu.
Could be, but just as easily could not be. Seems to me there is a lot of what ifs and assumptions made, and the fact that they first discovered this now, and only with one type of fish, does not prove macro evolution. Who knows, it could be a fluke, or a character specific to the fish and not the rest of the animal kingdom. Not to mention what mutations do to the human biology.
*** Eyewitness accounts are notoriously faulty.****
This eyewitness account is from the Book upon which the philosophy, theology and legal structure of historic western civilization are based.
Let's give is a bit more creedance than some UFO nut.
All freedoms are ultimately derived from the existence of God ("we hold these truths to be self evident...").
If you abandon God it won't be long before you will also be forced to abandon your freedom.
About once a week, our local paper prints a letter that usually goes something like this
I am a Registered Republican who proudly voted for Ronald Reagan/Dwight Eisenhower/Teddy Roosevelt. However, the recent actions of George W. Bush/Bill Frist/Ted Nugent in riding rough-shod over our Bill of Rights/Right to Privacy/Precious Bodily Fluids have convinced me that the GOP is now a shadow of its former self/nest of vipers/cabal of Satan-worshipping aliens. I am marching right down to my Town Clerk and registering as a Democrat/registering as a Green/marrying my dog.
Of course, nobody but a gosh-darned fool would ever believe this person was ever an actual registered Republican. It's just that some people think it's more convincing to pretend you have an open mind and have been led to your present position by the evidence.
I would suggest you smart people get you stories straight so those of us interested don't have to keep pointing out the contradiction
Feel free to start anytime, oh great skeptic.
So does nature, in atomic bonds. Ever examined a snowflake? Definitely a pattern there.
The first nation peoples don't matter?
Yeah, paleontology also includes guesswork, a lot of glue and spare parts.
Hell, my atheism evolved long before I knew anything about evolution. It was quite a number of sciences other than biology that fed my skepticism as a teen.
Exactly. So, knowing that there is a pattern does not tell you whether or not something is the result of naturalistic processes or of agency.
The difference is that genetic patterns are quite different than the patterns you mention. Crystalline structures are not information carriers, while DNA structures are. DNA is a carrier to coded information, where the code is distinct from the carrier. In the situations you mentioned, there is no code, only a patterned carrier. So, in DNA, not only do you have a pattern (long sequence of nucleic acids), but also information coded on the carrier, which itself codes for patterns, but not patterns that are made deterministically by the structure of DNA itself.
This is evidence for an agent writing a code.
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