Researchers Trace Evolution to Relatively Simple Genetic Changes

Howard Hughes Medical Institute ^ | 25 Narcg 2005 | Staff

[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.

Wild populations of stickleback fish have evolved major changes in bony armor styles (shaded) in marine and freshwater environments. New research shows that this evolutionary shift occurs over and over again by increasing the frequency of a rare genetic variant in a single gene.

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.”

[darbymcgill]

"Also, in your DNA there are large stretches of genes that don't code for anything any more because they are turned off."

Maybe some of the really smart people in this group with a whole lot of letters after their names ought to just flip a few of them back on and crank out a half a dozen of them Neuquenraptor argentinus just to prove a point.

BTW. Who turned them off in the first place? A meteor scared it off, or "maybe" a random lightening bolt? That lightening stuff is always turning off the most random things at the most random times in my house. But it still hasn't turned my wife into Shania Twain when the lights came back on.

[Right Wing Professor]

Obviously I was not being literal in relating shrimp to human beings and I think most people are aware of that.

Don't see why they would be aware of that. On the contrary, I'd say it's unsafe to assume any biological knowledge at all from someone who denies that lions and tigers are different species.

As for what science deals with - of course until a theory has been PROVEN, whatever evidence exists only supports a THEORY

Science does not positively prove anything.

Evolution is one of the few, if only areas, of science where I read scientists arguing that PROOF is not necessary - only the theory

I doubt you know enough scientists, or have read enough science, to make that call. But in any case, it's completely bogus.

[dartuser]

Small beneficial mutations are proof of macroevolution.

Presumption.

[dartuser]

You need to brush up on your Hebrew ...

[bobdsmith]

We don't "KNOW" anything about evolution.

IMO you are setting the bar for "knowing" arbitarily high, to a point where just about everything is unknowable.

For example do we know the romans existed? Sure we have historical documents, but we don't know for sure these haven't all been fabricated. Your definition of knowing seems to suggest that if I haven't directly observed the roman empire with my own eyes then I can't "know" it existed.

Also we can't possibly "know" anyone is guilty of murder unless we directly observed them committing the crime (we can't even trust witnesses as we can't "know" they are telling the truth).

It is merely a theory with no facts or proof behind it. I have gone over this over and over again in this thread and I stand behind each and every one of my points.

Evolution is not using some unique methodology. What you throw at Evolution you could equally throw at quantum theory, plate techtonics and germ theory. None of them have "proof".

Saying it is so, doesn't make it so. As another poster put it so well a few posts ago, it seems every time an evolutionist comes up with some new "evidence" of evolution is it merely another variation within the same species, i.e., a mutation resulting in lack of armor in a sticklefish. It doesn't matter if a sticklefish mutates with or without armor. It is STILL a sticklefish. It is STILL a fish. It hasn't changed into another species.

It is a different species of sticklefish. So yes it has changed into another species. If you are setting the bar higher than the species level then say that. I am currently in another debate on another forum where I have a creationist telling me that they accept all 350,000 species of beetles came from about 50 original beetle species on the arc. It's hard to find any common ground between those who attack evolution, because I suspect they are making up their objections as they go along.

I am sick of the arrogance of evolutionists, well demonstrated here repeatedly, and your jesuitical faith in your THEORY

You think it is arrogance but I have encountered the arguments you have put forward before and thought about them quite a lot. After looking at the situation I have come to realise that evolution uses the same scientific principles as any theory, and they are principles that over time add to knowledge and converge on a good model of the phenomenon being studied. Your position is basically one saying that science cannot determine anything about the past whatsoever. That is sad.

You have no proof of your theory, and you don't even understand the mechanics of it yourself. Unlike gravity you cannot demonstrate its effects.

We haven't even discussed the mechanics of it. I can demonstrate the effects of evolution. A nice chart of the hominid fossils does that nicely.

The effects of gravity are masses moving together.

The effects of evolution are: -transitional fossil forms -strict patterns to fossil distribution -strict patterns to geographical distribution of living species -strict patterns to shared genetic material between species

All of which are repeatable observations.

You merely point to similarities between or among creatures in the fossil line and use your "imagination" as an earlier poster put it, to postulate the relationship between different organisms.

In the same way that if I found two very closely related human DNA strings I would use my "imagination" to posulate the relationship between them. I see no inherent weakness with this approach. And of course we are not just comparing functional DNA, but also the errors that have accumulated through time. If two books have the same error on the same page then it seems quite absurd to imagine they were created independently.

As I stated before, you cannot conduct (as of this point) an experiment that consistently produces a physical result that demonstrates evolution from one species to another, or from a lower order to a higher.

Noone can conduct an experiment that produces a full orbit of pluto either. But that doesn't mean pluto orbiting the sun is just a guess.

In addition, you have no direct observation of evolution (not variation in a specific species like a flower, but evolution from one type of being to another type)in over 2000 years of recorded history.

A flower is not a species. Even if I had an example as dramatic as a rose evolving into a daffodil you would claim "but its still a flower". I suppose if I had an observation of a chimpanzee evolving into a human you would say "but its still an ape". There are examples of new species emerging, but you will just say "but its still an X" so whats the point? Wll here's one observation of a new species of mosquito anyway: link

[blueblazes]

Could someone else take a turn arguing these highly arguable points? I don't have time to do anything at length today.

[Dan Evans]

Imagination is NOT science.

Yes. But Imagination is part of the scientific process.

Science is ONLY demonstrable proof - a result that can be reproduced or predicted.

A theory never becomes fact and it is only "proved" to the individual. There was no particular moment when the Newton's theory of gravity was "proven". If an individual does not accept the proof, it wasn't proven to him.

[Dan Evans]

It has not evolved into a different SPECIES.

But there are all kinds of cases where crossbreeding has resulted in offspring that could not mate with the members of the original species. By definition, that means it is a different species.

[VadeRetro]

You basically need some kind of religious horror or other cult attachment. The Raelians would be secular skeptics if they weren't a cult with aliens as God. They reject evolution because the alien civilization that fills the God role in their cult can't do its job if evolution is doing it, same objection as Bible Belt creationism.

Also, you have to ask yourself how a supposed secular skeptic thinks the diversity of life on Earth arose if it didn't evolve and God or somebody with similar powers didn't make a whole bunch of separate creations. It may not come down to "evolution or God," but it certainly comes down to "common descent or separate creation."

[blueblazes]

Briefly, I think where we are having trouble here is with the word "species" and how it relates to the evolution argument. To the layman, of which I of course am one, species refers to entirely different orders of creatures - a mutation from one plant to create another somewhat different plant maybe technically be the creation of a new species in scientific terms (or we could say the same thing of an animal), however that is not what evolution is about. A plant is still a plant is still a plant. The whole point of the theory of evolution is about the mutation of lower orders of creatures, from the very lowest, into increasingly complex organisms - the whole march as I've put it before, from the amoebas of the primeval ooze, right up to man. I don't think most people, even religious ones, would deny that mutation exists and that obviously it has been observed. But the mutations have happened at what I might term in my clumsy language, laterally. We have no observation or proof of any lower order of creature evolving into any higher order of creature - we just have proof of lateral mutations.

Thus a plant is still a plant is still a plant. It has not evolved into anything other than a plant. A fish is still a fish is still a fish. It has not evolved into anything other than a fish. It may be a different type of fish. But so what? For evolution to be provable to the masses, there must be PROOF -not postulation, but PROOF, that there has been a progression from lower creatures to higher. This is what I am saying has never been observed and is not currently provable.

I really should stop spending time on this.

[DannyTN]

"It's a dramatic change: a row of 35 armor plates turning into a small handful of plates - or even no plates at all.”

Sounds like devolution to me. The fish started with 35 armor plates. And lost them. No new functionality at all.

[blueblazes]

I would be far more impressed if this fish had grown legs or had mutated to the point of being able to breath air. Losing scales - blah, so what?

[darbymcgill]

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

Since it is obvious you are more concerned about my motives, than my arguments, I will list a few for your enjoyment. That way maybe you can include me into one of your defined "labels".

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

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.

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.

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

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).

Those are the kind of contradictions that give me pause. Either you have the evidence or you don't. If you don't that's fine, keep looking. But please don't insult me and call be dumb-dumb because I don't buy you're version of the facts.

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? 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.

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. This causes me concern and dictates that I make my own decision based on credibility of the evidence, logic and of course, my own bias.

[Labyrinthos]

The problem with evolution is that it is a very broad theory based on - as another poster originally put it..imagination.

Immagination? You mean like burning bushes, parting seas, a massive 40-day flood survivied only by the inhabitants of an ark that contained two of every spieces of animal in existance, the belief that the entire human race is the incestious offspring of two people who met in garden shortly after a god created the entire universe as we know it over a seven period a mere 4000 years ago.

[Dan Evans]

When you try to demonstrate your theory, you keep doing so with examples that are only variations within a species.

But since we know that changes occur that result in offspring not able to mate with the parent species it is technically a new species.

Like with the theory of continental drift, no eyewitness has seen one continent break up into two even though we can measure the drift of land masses. But Africa is always Africa and South America is always South America. Likewise we don't see frogs evolving into giraffe.

[flevit]

no additional genetic information either.

[Right Wing Professor]

Sounds like devolution to me. The fish started with 35 armor plates. And lost them. No new functionality at all.

So in your book, a F16 is less advanced than an A10?

[blueblazes]

So? Who said I believed in that either? Some people believe in the Star Wars idea of worlds full of aliens. So what? People can imagine anything from a supposedly "scientific" or technologically based idea to a "religious" one. It's all imagination, which is fine. It's just not...science.

[KeepUSfree]

Gotta chime in here - as you just don't get it (or don't want to). No, by definitinion, a "theory" cannot be proved. Were it "proved" it would cease to be a theory. Evolution is a "theory" that 99.9% of all evidence collected so far, fits with the theory.
The best analogy I know of is that of Gravity. Do you believe in gravity?? I would bet "yes". Do we know WHAT causes gravity? - No, Do we know WHY there is gravity? No. Do we know where gravity came from?? ...no. We are CLUELESS. However, gravity does seem to exist and we can predict it's effects, it's strenghth, and when it will occur - all due to the physics of "Gravitational THEORY". It is a THEORY which all of the facts SEEM to support.
Same thing for evolution.
Next, I despise "why doesn't a fish turn into a baboon" statements. They are childish, simple and insipid and show the feeble mentality of the speaker. Finally, you flat-earthers do not comprehend the amount of time involved in "600 million years". Just to give you some perspective. 600,000,000 years is 300,000 times longer than the amount of time since Christ was on this planet.

[blueblazes]

We can see the process of land changes today, and we have been able to observe them for thousands of years. Islands rise and fall, lands that once existed are covered by sea, others are exposed. Lakes evaporate or are sucked up overnight. Tropical areas become desert and vice versa. Icebergs break from polar regions. Earthquakes and volcanoes produce obvious and dramatic changes in land. Even the recent tsunami in Asia was felt all over the globe literally (it shook the planet and I believe moved it a fraction). All of this is demonstrable and has been witnessed and measured repeatedly. Unlike evolution. There is no comparison.