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.”

Did nature invent E or pi, or are they constructions of humans trying to understand E or pi?

These numbers are not a constructions of humans. We know that because different people using different techniques always arrive at the same value for these numbers independently. An alien culture on another star in another universe would still find the same value of the ratio of a circle's circumference to the diameter.

The number would always be the same regardless.

Occams razor is something scientists take as a matter of faith and so far it has worked. And it implies that, when we find it, the ultimate rule of the universe will be pure and simple.

Fractals are a human construct. One made to mimic nature.

Backwards. Nature obeys the mathematical rules of fractals.

The laws of physics tend to get more complex under extreme conditions. To me, that fact means that we haven't discovered the real laws. What does it mean to you?

If you want my beliefs, Nature does not give a hoot what we believe.

If an alien species developed a non euclidean geometry that includes "stuff" we do not percieve, how can you be certain that it will derive the same conclusions we do?

Nature obeys the mathematical rules of fractals.<<

Ohh, you made my head hurt. Nature does not obey any rules humans make. Stomp up and down and make it rain. We're back to ID and faith. We test and make rules in order to understand Nature better, not the other way around.

The laws of physics have been mere constructs, and Occam's razor says that the simpler construct is the better tool. It is a fallacy to confuse the tool with the phenomenon.

E and Pi are tools for understanding.

To me, I think the next few years are going to be great, and wonderous things will happen in science. Many sacred cows will be turned into hamburger.

We are cursed to live in exciting times.

DK

Doggone it JS1138!!! that is back into the arena of faith. I don't want to go there. LOL

It is not a matter of faith any more than the weather is a matter of faith. Evolution and weather are deterministic systems that cannot be fully predicted. In the case of evolution, one can say that populations change in ways that adapt to changing environments. But most of the species that have ever existed are extinct. So there is no guarantee that adaptation will occur or will be successful.

It was a minor joke, but based in truth. If a population does not react to either a direction, nor a result and NS is also inappropriate for probability studies or quantification, how do we evaluate it?

As I have said before, rigorous science will, and not like it has been done in the past. That ticks off current evolutionists, because they just don't have the skills to do the science.

Weather prediction is crap science. A couple of years ago, NYC was shut down because of a major snowstorm that would hit NYC 24 hours later. The storm missed. Billions of dollars were wasted on a crappy prediction that was less than 24 hours away.

With the weather, we have constant feedback on accuracy. NS does not have that scrutiny. Would it survive if it did?

Given those caveats...no direction, no results or predictive qualities, and no probability potentional for predictive behavior. How does NS even rise to the standards of a theory?

LOL

DK

Remember, squishiness is a bad thing. Evolution is not a theory, NS is.

If I asked for any data that would help NS as a useful working theory, I would be inundated with thought experiments, crazy and mostly trivial germ theory (there was a post by a maniac in a lab that I would exempt from this comment!). Nothing that would help me predict tomorrow's weather, or my cat's fur color.

Without administrators, most MIT profs couldn't find their arses with both hands, a flashlight and a whole book of quadratic equations. This is exactly the kind of superior attitude that I found so obnoxious at MIT and am so glad to be away from now. The hospital I'm working in currently has exceptionally decent people. It's refreshing to be treated with respect for a change and to have one's work valued. Perhaps some day, with the passage of sufficient time, the posters on this board will evolve some social skills so they can intermingle with the rest of us.

If you want my beliefs, Nature does not give a hoot what we believe.

I agree, but that's because I don't personify nature as you do.

If an alien species developed a non euclidean geometry that includes "stuff" we do not perceive, how can you be certain that it will derive the same conclusions we do?

If they had a different geometry they wouldn't. Pi depends on plane geometry.

Nature obeys the mathematical rules of fractals.<<

Ohh, you made my head hurt.

So take a pill.

Nature does not obey any rules humans make.

No, but sometimes we discover rules that nature obeys.

Stomp up and down and make it rain.

Now who's being silly?

We're back to ID and faith.

Not me. I don't believe in intelligent design. But I do have faith in truth. And I have faithe that the world obeys simple rules.

We test and make rules in order to understand Nature better, not the other way around.

Don't you think that nature follows rules?

The laws of physics have been mere constructs, and Occam's razor says that the simpler construct is the better tool. It is a fallacy to confuse the tool with the phenomenon.

I think you are arguing semantics. If we discover a rule that we observe nature to always follow then isn't it correct to say that nature also follows that rule?

E and Pi are tools for understanding.

Universal values. The same values here as on Alpha Centari.

Uh hunh,
You don't like MIT profs. Got it.

Now I repost this from you to another poster:

"...Darby, I actually worked at MIT for about a dozen years and have worked in various other academic and research institutions before and after. The atmosphere and method of "teaching" that you so eloquently describe in this post does indeed prevail in most of these institutions. It is not about "learning" or "proving" or "discovering" or "research" as much as it is about parroting back the establishment's dogma and re-confirming what they already believe. If some one does indeed come up with something truly different or inventive, or that deviates from the mainstream establishment belief, they are indeed treated like heretics and may face consequences for their actions ranging from ridicule and snickering all the way to being nearly forced out of their positions or not getting tenure. I've seen this...."

And you learned all this from being an administrator? Did you attend the classes you criticize? Did you attend departmental seminars? Attend tenure track or research evaluations?

Did you have any time to do your own work? Why do I think this is another case of spider agave level observations?

Perhaps some day, with the passage of sufficient time, the posters on this board will evolve some social skills so they can intermingle with the rest of us

I guess the assumption you're making is that we'd want to.

Social skills around here are just fine. Problem is, some of the people ranting against evolution here would turn Will Rogers into a misanthropist.

I suspect you didn't get along at MIT because you have a chip the size of Texas on each shoulder. Most MIT profs I know are pretty easygoing, but they dislike being lectured on science, an area of which they generally think they have a good grasp, by religious fanatics with a ninth grade education. You can call that arrogance, if you want. I think the real arrogance is assuming that, without putting in the years necessary to master a discipline like biology, you can spot flaws in it that people who have dedicated their lives to it have missed.

I think you and your cohorts have clearly demonstrated where you are coming from, and lurkers can make up their own minds based on the existing posts. We obviously have stopped discussing the topic and have moved on to useless personal baiting. I have no interest in giving you additional fodder for insults or ridicule. I'm sure you can find endless hours of mirth just sneering at the unfortunate adminstrators or non scientists in your own circle of work or acquaintances. Bon appetit.

If a population does not react to either a direction, nor a result and NS is also inappropriate for probability studies or quantification, how do we evaluate it?

Where did you get the notion that populations don't respond to results? Selection is a result. What doesn't happen, or at least hasn't been observed, is the anticipation of results. There is no observed correlation between mutations and reproductive success.

This is difficult to phrase correctly, but basically mutations are stochastic. In sexually reproducing organisms, billions of sperm are created for every one that results in conception. Many conceptions occur for every birth, and many births occur for every individual that reproduces. Darwin noted this as a malthusian overproduction, leading inevitably to selection.

Social skills around here are just fine.

Actually, this is a new criticism. I'm accustomed to being told by creationists, with science educations that never rise above the silliness of a Jack Chick comic, that they somehow have a superior knowledge of science. But now, we're told that these uneducated folk have superior social graces as well. And this claim comes from a group of people who routinely: (1) plagiarize; (2) quote mine; (3) never admit errors; (4) assert that all science is a fraud; and (5) engage in flagrantly disruptive behavior.

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