Researchers Trace Evolution to Relatively Simple Genetic Changes

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.”

"What's a spider agave? Or a tykva? Or a bird agave? Or a rossette plant? "

These are all....PLANTS. so what?

"What's a porpoise? Or a sea lion?"

These are aquatic mammals. so what? I believe their forebears have been pretty similar for millions of years.

"For that matter, what's a virus?"

Well, a virus is a virus - I think we all could look up the definition. What's the point?

What you and your cohorts resolutely refuse to address, presumably because you are unable to, is the evolution from lower life forms to higher orders, which is what the theory of evolution is REALLY about. That is it's most important point, not relatively minor mutations within plants or animals. As I have noted in many posts, what I term the march from the amoebas of the primeval ooze right up the food chain to human beings. What you consistently give as examples are plants or animals that are still....plants or animals, that merely mutate on the same level. Let me know when that porpose develops legs and starts walking around downtown Boston. You all seem to fixate on really - and now I'm going to get a bit testy - STUPID things, like whether a sticklefish mutates to a form without armor. BIG GD DEAL. When you produce a sticklefish that develops legs and walks on land, or starts breathing air, let me know. Otherwise your comparisons are pointless. You are just pointing to creatures that are similar to each other. Maybe they've ALWAYS BEEN THAT WAY! Or they've had fairly minor variations over time. A wooly mammoth is still recognizable as a type of elephant. It hasn't evolved into some other kind of life form. A mule, which I believe is generally the sterile offspring of a horse and a donkey, is still RECOGNIZABLE as a member of the "horse" family.

Thank you so much for returning to the civil, intelligent conversation I was so much enjoying earlier.

Please practice what you preach and spend less time telling me how to argue my side and more time addressing your own little difficulties. As for how much you were enjoying it, that might be because I've been the one posting all the evidence as you sat and airily waved it all away. Not much work in being an ignoramus, demanding various broomsticks being brought to you and then doing "maybe-counting" on the replies.

1. I believe there is much about the natural / supernatural world that is unknown and unexplained. But that does not discount it's existence.

Supernatural? Remember, you're not religious. But you're ... what? Superstitious? No God, but demons and magic and spells? What? Why do we need supernatural explanations? Oh! Right! Because we're running marathons of denial to sweep the 150 years of accumulated evidence for evolution under the rug.

2. I cannot begin to tell you how many facts that scientists have given us in just my lifetime that have eventually been contradicted or disproved.

Science makes revisions in a process of converging upon an increasingly accurate description of nature. That's one way it's not religion. It follows evidence and changes its collective mind to accomodate new evidence as such is uncovered. Furthermore, it actively seeks new evidence as part of this process.

The activities of all evolution deniers, whether they admit to being motivated by religious horror or not, do not look at all like this. They typically cannot admit error above the typo level and will tap dance about publicly in a transparently dishonest fashion--adults behaving badly--rather than admit anything when caught out. More to the point, they have no actual curiosity about how the world works. That, after all, is what they think they already know. It is just necessary to destroy "the competing worldview," or whatever.

Example. A group of scientists does some real research, learning something in the process. They publish their findings in Nature and announce them in a press release.

Jonathan Wells of the Discovery Institute in Seattle, the War Room of the ID movement, gets wind of the announcement and fires off a press release in rebuttal. It becomes clear in the aftermath that he was utterly unfamiliar with the design of the study and what it had in fact established. He just knew that his side needed to fire out a rebuttal ASAP because that's how Carville and Stephanopolis ran the Clinton War Room in 1992.

Science actually tries to learn something. The UN-Discovery Institute and the rest of UN-science tries to UN-learn it. They don't do a study. They may not even read the study that was done. They just sit down and type up a screed in rebuttal.

One of the two is doing something by which one may actually increase the sum total of human knowledge of the world. The other is frantically working to sabotage the first.

3. It is illogical to me that any "Intelligent Designer" would condemn a soul to hell based on where or to whom they were born.

This seems to belong to some other conversation somewhere. You're not doing very well in the lucidity department. I have not discussed Hell or the afterlife, nor do those concepts fit neatly into whether evolution has occurred. Try to remember that it's your story, not mine, that you're not religious.

4. I must admit that I am not a scientist. I have only three letters after my name, none of which is a 'd'.

Hey! No Shiite, Sherlock! But somehow you know the science since 1859 as practiced by the people who studied for careers in science is all wrong.

That being said, you and others of your ilk try to convince me that we have verifiable evidence that traces human life back to an amoeba sans flagella or earlier. Then I see the professor later say no, no, we never said we can trace all life to a single source, all we are saying is that man evolved from apes (or something similar).

You don't do a very good job of recapitulating the other side's arguments. That would look bad even if you had no other problems. Yes, humans evolved from apes. No, that's not all we are saying.

Those are the kind of contradictions that give me pause.

You are inventing your own contradictions with your pig-ignorant strawmanning. I seriously doubt that such is the origin of your willingness to bend at the waist backward to deny the evidence of science.

Do I eat salt or not? Did aliens visit the Aztecs and draw those things on the ground or not? What about black holes, worm holes, global warming, extinctions, yada yada yada?

What indeed?

There are all kinds of "scientists" trying to tell me "I just don't know enough about the subject material" if I don't buy their interpretation of events. I even read some Darwinists on this or some similar thread put those who believe the scientific proof of global warming along with Creationists, Palmists, and country music lovers.

Science converges upon an increasingly accurate description of nature. Thus far, it works. Stay as militantly confused as you wish.

Scientists are people with biases just like priests, imams, monks, etc. that are trying to explain unexplainable events. So as long as I'm getting multiple versions and interpretations of the same evidence by different scientists and/or clerics, I can only assume it is the training or the bias influencing the results.

See my response just above.

You are militantly unacquainted with what evolution says and what the evidence is. You so far appear innocent of any exposure to logic. As for you having a bias, you have denied that any bias is religious in nature, which is rather odd in one who does not accept common descent. As already pointed out, common descent and some kind of separate creation really are a logical dichotomy.

You're phoney through and through, sorry. Learn to spell ID.

Oops. Didn't take you long to de-evolve did it.

Please make reference to to post where I posted I was or was not religious. All I ever posted was that I didn't have a dog in the hunt.

And now I'm an ignoramus. What an astute rebuttal. I won't waste my time addressing your ad-homeinum attacks. But I guess that makes you the winner because you called be a bad name. Is that how you scientists treat each other in the esteemed "modifications" of enlightenment you make. Do you "converge" on the most serious of names to produce current scientific intrepretations or just call each other doo doo heads until someone gives up and says. ok you win.

I guess people like you are never wrong. You just modify your positions to fit the current interpretation. Kinda like Bill Clinton. What you believe is all relative to what the other scientists think about you.

I bet you knew all along the Felt was Deep Throat didn't you. Even if you thought it was Al Haig, I bet you just modified your thinking to pretend that you really thought it was Mark Felt. You weren't wrong. And anyone who disagreed with you when you told them it was Al Haig, I bet you called them a ignoramus because they couldn't give you a peer reviewed publication to prove you wrong.

So, once again you screamed the loudest, called me the most names and never once addressed my arguments, i guess that makes you the WINNER.

Chaulk one up for Vade on the converted secular skeptic of evolution ignoramus score board. He didn't beat him with his agruments, but he was a great name caller.

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.