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.”
Bingo. You are learning. Evolution does not specify a direction or results. That is why probability calculations are irrelevant.
And your only response to my comment is to insult me? In that one post you have illustrated the very problem that I described. Of course, you don't have to explain the question to ME personally, as I really don't care and am only picking up the question rhetorically, however, your reply clearly indicates what your response would be to people who genuinely don't know. Perhaps not everyone has had the same biology training you have had, or may still have questions. Are you able to actually answer those questions or can you only ridicule people who ask them?
Someone has probably told you by now that proofs are for geometry class, not biology class. Science works from a preponderance of evidence. There is an overwhelming preponderance of evidence that life on Earth is related by common descent through variation and natural selection. The preceding, you will note, is a link. You click on it and get a high-level (but footnoted and bibliographied) summary of the evidence.
I don't want to keep repeating the same thing over and over. I'm tired of it myself and it just gets to the point of nyah nyah nyah....anyway, my opinion is out there to whatever extent you want to check it out.
Yes, an intelligent dialogue only happens when you answer the answers to your point A and don't simply repeat your point A ad nauseam. So far, every attempt at intelligent dialogue with you has fallen one intelligence short of an intelligent dialogue. You are in fact displaying all the symptoms of militant ignorance. But then, Creation Science seems to be the militant "You Can't Make Me See" science.
"...My posts are mainly about lack of proof on the part of evolutionists for their theory...."
No, your posts are mainly about your inability or refusal to study and understand the evidence. Sort of like spider agaves.
In case you are curious about hyena evolution, this is a fairly nice, and brief, synopsis: http://www.wearesites.com/Personal/Hyenas/hy_evolution.php
They are truly interesting animals. There are only four species of hyena today, but the fossil record shows at least 69 species in the past. While they are classified as a family of their own (the Hyaenidae) they're more closely related to cats than dogs. Go figure.
OOPS. I see now that Vade already directed you to that site about hyenas. In any rate, it's worth a look.
Of course not. It was all already in the DNA. :-)
Exactly. Funny how guys with Science PhD's can't distinguish between "previously in the DNA" and "not previously in the DNA."
Ooops. I was supposed to "be nice."
Whole populations evolve over time. That is the Darwinian model. Every population visibly now has a whole swarm of variable characters, each such character having extreme cases and a population average for each. Natural selection prunes these experiments, rewarding some variations with great success in feeding, growth, and reproduction. The unviable or out-competed (or just unlucky) fail to reproduce.
The whole population changes over time. Nothing is ever so different it can't mate with the rest of its herd/flock/whatever. If it is, it fails to reproduce.
Let me anticipate the usual lawyerly squawks which will come flying in from somewhere. Caveat One: There is a form of "instant speciation" called polyploidy which mostly happens in plants and some invertebrate animals. When it happens, the mutant strain can only reproduce asexually at first, until there are multiple compatible individuals. Compatibility with the parent strain is lost in one generation.
Caveat Two: Punctuated equilibrium is Darwinian evolution. It is not Goldberg's "hopeful monster" theory and it only looks fast in the fossil record. Nothing spectacular happens in one human lifetime.
The preceding two paragraphs are an experiment. Will "forestalling" the usual "rebuttals" prevent some ninny from posting the challenge after it has been answered?
In summary, the whole question you defend as legitimate is not a valid criticism of Darwin's theory or anything related to it. It has no place in science class except perhaps in a "How to spot crackpot science" segment.
That was my point in mentioning it. People who claim to have studied evolution before they "looked into creationism" don't ring very true, as they necessarily have accepted very ill-informed and utterly fallacious strawman attacks on what they supposedly learned previously.
Thanks, but I'm leaving this debate at this point. I've said pretty much everything I can and I'm repeating myself. Frankly, I have to agree with Darbymcgill's observation about many of the posters on this thread. Many of them are positively nasty, rude people who seem unable to have a civil debate and who look down on everyone who doesn't automatically share their opinions as somehow inferior intellectually or academically. I saw too many of these types in 12 years at Massachusetts Institute of Technology - in fact, in 30 years of work, the most despicable, vile, rude, vicious, hostile, backstabbing and just nastiest people I have ever met were many of the professors and scientists of MIT. I was so relieved to "escape" and frankly in reading these posts I'm having a sense of deja vu. So, I'm off to other topics. Thanks for the link, though.
We've heard that a million monkeys at a million keyboards could produce the complete works of Shakespeare. Now, thanks to the Internet, we know that is not true. ~ Robert Wilensky
......evolution can occur quickly....
Macro Evolution.....
Stephen J Gould would say, did say actually, the phenomenon can be called punctuated equilibrium. The gene research provides a cause for his observations.The changes in the population can come quickly and stabalize in the population.
He got most things right in spite of his Havard Yard manners and failure to understand his own racial bias.
Bingo. You are learning. Evolution does not specify a direction or results. That is why probability calculations are irrelevant.<<
Natural Selection as the mechanism does. Filling the niche is the criterion. Who does it better? is the question.
If NS was a useful theory, quantifying it would be a useful goal. Instead, it is mired in glop terms and useless thought experiments.
Molecular geneticists may do precisely that, quantifying evolution. I'm excited about that.
DK
I am curious about one thing. If Evolution can't tell you anything about direction or result...and cannot be quantified, and the laws of probability do not apply...
Doggone it JS1138!!! that is back into the arena of faith. I don't want to go there. LOL
The evos on this forum consistently back up what they post with links and excerpts from actual, hands-on research. I can't believe you've missed out on Ichneumon's massive postings in the past.
I guess you just don't get the point, but as I say, I'm done.
But, of course, you don't want to admit it, so you're "done with this conversation."
What department in what building at MIT, in what role?
I have worked in a number of depts at MIT as an administrator. Obviously I don't want to be too specific in this forum. However, you remind me somewhat of a professor I used to work for in EAPS in Building 54. You would know what that is.
I have worked in a number of depts at MIT as an administrator. Obviously I don't want to be too specific in this forum. However, you remind me somewhat of a professor I used to work for in EAPS in Building 54. You would know what that is.
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