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.”
> How to you explain that evolutionists themselves tend to chart the species as below with nothing having a "direct" ancestor
False assertion on your part.
Explain.
The word "theory" as used by biologists and scientists does not exactly mean theory in the everyday sense that most folks would use it.
They never say that out here, but it is so.
"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."
In a stunning example of magazine-articles-intended-for-funding-agencies-and-federal granting-agencies, these scientists have once again proven how microevolution can produce fewer armor-scales, never turning a fish into a baboon or bassoon or a jousting knight.
Scientists to granting agencies: we haven't been able to sell our huge, complex books of charts and graphs and evo-babble, so let's try the simpler approaches now.
I'm thinking troll. Pretty good one, too
Right Wing Professor has a right to call attention to my lack of attribution. He's been around long enough to do so. But you having less than 30 days here on FR and only posting on Evolution threads (with a decided lack of civility I might add) one might think you have a scent of a troll on you.
Should have pinged you on the last post
I'm told earlier in this thread that "by definition" there is no breeding across species, how dumb can we be.
Species are human constructs. If two distinct groups of animals don't naturally breed with each other, we call them distinct species. That doesn't mean that under artificial circumstances, they'll never breed with each other.
As to your question; I have no idea; you continually exceed my expectations.<<
IIRC the normal definition of species is that which can produce fertile offspring. Evolutionists (NS) have devolved (LOL) the definition to fit the hypothesis. NS Evolution went squishy because of it. It should have been a scientific embarassment, but they kept plugging away.
Do I believe in NS Evolution? There have been a number of posts on this thread that are analyzing the genetic data with rigor and specificity. Those are the interesting ones. And they have the added possibility of a real mechanism being understood.
Morphology and the fossil records posts are rather uninteresting. You know the arguments, millions and millions of examples of NS Evolution, but only taxonomy and morphology to depend on. A rather circular argument without adding use to the theory.
Have fun!
DK
Civility is as civility does. Or something.
I'm sorry if my posting history bothers you. I have a keen, albeit layman's interest in biology, paleontology, and certain extinct animals.
I'm also really interested in fishing. Believe me, when a thread pops up where someone claims that everything we've known about fishing for the past 150 years is a lie and possibly part of a communist conspiracy, I'll post on that thread too.
I'm sorry if my posting history bothers you.
I find your posting history interesting, not a bother.
You're assuming an environment where the prior distribution is linear; e.g., no particular sequence/distribution of letters has a higher probability of being generated than any other. You also assume that there has to be only one end sentence (humans in your analogy), when any legible sentence would do (any self-reproducing machine as a whole).
Yes, I talk to myself. "Old Bachelor's Disease." I have a disease-name for everything.
You can say that again.
Z' = Z^2 + C
There was really no other information. No artist drew it and it wasn't a product of evolution. Yet it appears to have patterns and appears to be a product of intelligent design.
Might have been an important insight when he had it, but he slightly mistook the underlying mechanism. He has Venus entering the Solar System as a comet and pinging around among the planets like a big pinball to do most of the damage. 98 percent of his story is laughable, starting with the fact that Venus was being observed as the morning and evening star by Sumerian astronomers at the dawn of human history.
Enough of your slimes!
Evolution threads on FR are the most contentious wastes of time. You just have to have the right attitude, no one is either going to prove anything (I loved the section of this thread where someone said nothing is proven in science, ignoring proof which is supportive of a position) or advance a major change in Evolutionary THEORY.
They can't even figure out if the fifty species of Sticklebacks are really subspecies and the originating article is just a bunch of hot air.
Ask biologists how many chromosomes we have, and see if they say before we had forty eight, but now it is forty six. Or how a bird population can be isolated, (that story of an American bird in England, from a jet stream assist)...or many other stories that just scream this is not a perfect world.
But if you like, take these threads as I do. Exercises in proof and logic, with a minor amount of new information in between. Very minor.
In another thread I found out about Goatsbeard, the only case of speciation that was not from a squishy definition of species. But there was no NS foundation to the new species of Goatsbeard, at least that I recall. But it was speciation, in our eras.
Hard biology will show significant, replicable and interesting stuff. Morphology, and taxonomy will make fine museum exhibits, until they are replaced.
Everyone here knows that Steady State Universe was undeniable to the scientists pre Einstein. Quantuum Theory, Plasma Theories, and String Theories are not compatible with Einstein and the Big Bang, but they have useful things to pose in physics.
Lurk DarbyMcGill, and if you show up on a Creation/Evo thread again, and "can't find a REO, I'll Fly With You!"
Besides, these threads can go up to 2500 or more posts. Everything after 500 is a waste.
DK
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