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.”
I don't think most critics of evolution would dispute that your pics might constitute a limited form of micro-evolution, or at least the possibility thereof. But for the picture to be complete, you'd have to take the evolutionary line a lot further back than you've done there. And as far as I'm concerned, the problem with the theory of evolution is that it does not very well account for the beginnings of the process, the development of complex molecules, amino acids, proteins, DNA, etc., i.e., how the whole process overcame the law of entropy and the laws of probability. You would have to posit some organizational property inherent in matter that would be almost equivalent to intelligent design.
***I speak no more to fools.***
Honestly, how can you as a Southern Baptist deacon use such dismissive language of those who hold to the truth of the Bible?
Either you don't really believe evolution of you don't really believe your stated faith.
..."why haven't we found any real examples of intermediate species anywhere in the fossil record." - BB
Perhaps you are looking in the wrong place. If you want to find intermediate species maybe you should try watching the westminster dog show.
The toy class may soon enough (2,000 years?) be a different species from the large breed classes. They already face great difficulty interbreeding, which is one aspect of speciation.)
***Southern Baptist deacon***
Sorry, I see you were refering to your father.
P.S. Saying "Good Bye! I speak no more to fools." while engaged is a soliloquy (from soliton to soliton) gives a very humorous impression!
So how long does it take a toy poodle to evolve into an orangutang? Or a grizzly bear? You're still talking about a dog changing into another type of dog - whatever the size or appearance.
> your pics might constitute a limited form of micro-evolution
BWAAAAHAHAHAHAHAAAAA!!!!!
> you'd have to take the evolutionary line a lot further back than you've done there.
I haven't the time to do all your Google work for you.
> it does not very well account for the beginnings of the process
It does not claim to. That's in the realm of chemistry, not evolution.
> how the whole process overcame the law of entropy and the laws of probability
It has not "overcome" either. It is well in accordance with both.
Oh - and the difficulty with inter-breeding might be related to relative sizes. It's probably difficult for a chihuahua and Great Dane to mate and I can imagine motherhood would be rather difficult for the chihuahua.
> Now, if it takes THOUSANDS of years to get something as small and insignificant as the shape of a beak to change, then how many MILLIONS (billions?) of much more significant changes must take place for a single celled creature to evolve hundreds of organs that all function interdependently and turn into a human?
About 3.5 billion or so.
Your "never answered" question is now answered. Go forth and sin no more.
These animals did not exist for the entire scope of 3.5 billions years. If we attempt to follow one recognizable animal over the course of its duration on the earth we probably would only be into the millions. Even sharks, who are one of the oldest continuous species on earth, are still recognizable as sharks - whether several million years ago or today. Why didn't sharks evolve? Or did some of them evolve into something else? What?
The problem with evolution is that it is a very broad theory based on - as another poster originally put it..imagination. THere is no proof of it because proof is science is the ability to reproduce a result. We cannot do that, nor have we seen that to happen in nature during the recorded history of man.
> often I think scientists are using THEIR imagination and wishful thinking by assuming that animals who share common characteristics or appearance are descended from or related to each other.
Genetic analysis. Look into it.
> do cats and dogs have a common ancestor because they have some characteristics in common?
Yes.
> Where is the proof other than visual similarities?
There is rather more to paleontology than just looking at bones.
As usual, no REAL answer is provided. Just "It happened", without questioning those who gave you the 3.5 billion year figure.
The biggest sin that an evolutionist can commit is to question the theory. In that area you appear to be blameless.
> Why didn't sharks evolve?
Sharks *did* evolve, and continue to do so. The species fo sharsk alive today are not the same as the species of sharks alive 30 million years ago. The body forms remain similar because the form is emminantly suited for the role of fast predator... there is little room for improvement there.
> We cannot do that, nor have we seen that to happen in nature during the recorded history of man.
Wrong. Do some research.
You missed the day in math class when they explained the difference between thousands, millions and billions?
Crocks and alligators are pretty much unchanged for 200 million years. Evolution doesn't say things automatically change. It says that variations differ in the number of offspring they produce. Sometimes the originals are good enough.
The scientific method. Definitions of "theory," "hypothesis," etc.
The scientific method. Another site. Exhaustive discussion.
What's a Scientific Theory? Encyclopedia article.
The Theory of Evolution. Excellent introductory encyclopedia article.
Is Evolution Science? It certainly is. Here's why.
Evolution and the Nature of Science. Excellent discussion.
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> without questioning those who gave you the 3.5 billion year figure.
That's because those who honestly search for the answers keep coming up with the same ones. Determining the age of the earth and of the fossils it contains has been reduced to a fairly precise science. Look into that.
Genetic analysis? I don't think so. Many very primitive animals such as flies, if I remember correctly, share much of the same amount of DNA as humans. Does that prove that humans descended from flies? Of course not. Genetic analysis actually proves nothing in this case. All it "proves" is that all creatures on earth share the same common building blocks. Both a bridge and a building may be built from the same materials but they are not the same thing.
The only real "proof" in science is being able to reproduce a result or predict the result of an experiment. Anything other than that is a theory which should not be held too tightly and which one should be willing to displace with ease. The problem with theories like evolution is that they take the place of religious beliefs for non-religious people and they are held with the same stubbornness and illogic (and unwillingness to change) that religious people sometimes show.
As for the common ancestor of cats and dogs - what would that be and what is your "proof"? Of course, the great problem with evolution is if it is a ongoing process we should see some species somewhere in the process of evolving into a completely different species. As far as I know, no one has witnessed this - ever. Therefore, I cannot imagine that it is an ongoing process.
A shark is a shark is a shark. Sharks did not turn into baboons. A shark of today is far more similar to a shark of several millions of years ago than it is different. What different species did the prehistoric shark evolve into?
Stop telling me to do research. This is your theory, therefore YOU have to back it up.
None of that answers my original arguments so the points stand. Instead of just posting links, post your own thoughts, as I post mine. Evolution is based on observation and assumption, not proof. The only "proof" in science is being able to reproduce a result or to predict a result. To the best of my knowledge neither of these has been true of evolution. Everything else is theory. Theory can be good or bad, but should not be held as a religion.
And as far as I'm concerned, the problem with the theory of evolution is that it does not very well account for the beginnings of the process, the development of complex molecules, amino acids, proteins, DNA, etc.The reason, of course, is that you can only have evolution where life already exist. In other words, the theory of evolution doesn't cover the origin of life. What you're hinting at is abiogenesis.
i.e., how the whole process overcame the law of entropy and the laws of probability.The second law of thermodynamics is valid for closed systems, which our planet is not. We constantly recieve massive amounts of energy from the sun, and can thus locally overcome entropy. As for probability, it's what we've come to call 'Retrospective astonishment' (© PatrickHentry). For example, consider all the events throughout history that led up to you being born and eventually post on this board. Extremely improbable, isn't it?
Pretty pictures! ... Im totally convinced. How do I renounce my faith and join the family of "real" scientists?
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