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.”
The differences between parables and straightforward historical accounts are pretty obvious.
Unless, of course, you have your blinders on.
You've discovered patterns. Almost every designer I've ever known designs according to patterns.
True.
If you want to try and deny that this has historically been a Christian nation, founded by Christians, go ahead...but it's a tired and silly little game. If you can't even acknowledge such simple facts of history, the facts about what happened in the last 4 centuries or so, why should any thinking person give any credence to what you claim happened thousands or 'millions' or 'billions' of years ago?
I'm pretty sure it's ONE of the oldies but I don't recognize the hand thus far. Maybe it's a disciple?
I hate to tell you, but just because you have listed a creationist claim and made an argument, does not mean that it is refuted. There are many errors and fallacies in those pages.
Here's some links:
http://www.nwcreation.net/wiki/index.php?title=Talk.Origins_Archive
http://crevobits.blogspot.com/2005/05/talkorigins-index-to-creationist.html
http://crevobits.blogspot.com/2005/05/more-replies-to-tos-creationism-claims.html
However, I do appreciate T.O refuting those arguments which are truly bad.
Those kind of comments really aren't that witty.
The deity I mentioned fits your criteria of "the same Creator that Americans have always worshipped."
"The amount of time that it takes to produce even the minute changes they are noting, is significant in and of itself. To produce a major evolutionary change so that a species is no longer or barely recognizable from its "forebears" would take too long."
What's even worse, is that experimentally they've found that even when you hit upon the rare chance that a mutation is beneficial, the chances of two beneficial mutations being synergistic is very low. So not only are the beneficial changes rare, synergistic changes are really rare, with most interactions of even beneficial mutations being more harmful than good.
The question is aimed more to E.T., if God said "Thou shall have no other gods before me", to what other gods did God have in mind? Zeus, Odin, Cthulhu?
Here's two "thought experiments" for you to ponder (I realize that "thought", "experiment" and "ponder" may be a little too much, but you could always prove me wrong...)
1. E. coli can divide every 20 minutes (hell, B. stearothermophilus can do it in 8 minutes), yet it takes well over an hour for either to replicate their chromosome. How can that be?
2. Here's one for the less adept. It takes several hours to produce a car on the assembly line. Yet a car rolls off the line every few minutes when they're cranked up. How can this be?
PH, or anyone. Want to explain "critical mass" to the Australopithecines?
> Wrong.
Sez you. Which is the point.
> I worship the God of Abraham, Isaac and Jacob...as well as Moses, King David, The Apostle Paul, Sir Isaac Newton, George Washington and Abraham Lincoln, to name a few.
The Gods of Washington and Lincoln were quite unlike those of Paul, given that Washington was at best ambivalent (he went to church and mouthed some platitudes, but was noted for expressing privately virtually no interest) and Lincoln likely atheist.
I think I've figured out what's happening here. Every time we start a thread about some really neat discovery, one which is not only consistent with evolution, but which powerfully supports it -- like a change in one gene that makes a huge difference -- the hard-core reality deniers come out. The day the creationists ever discover anything that contradicts evolution -- or ever discover anything at all for that matter, so far their record is a flat zero -- will be most interesting. I'm waiting ...
"Huxley claimed that given enough time, a money at a typewriter could generate the works of William Shakespere."
(1) If that is true, I think Huxley underestimates how long it would take. I actually once ran a monkey-typing program to match it up against just typing the alphabet, and the computer could only get up to "C" within a few hours of typing (this was on an Apple II, though).
(2) This assumes that the words could stay on the page. In the biochemistry of the origin of life, a non-final form will cause the page itself to crumble. Not only would the monkeys have to type, they'd have to type fast to get it on the page before it disintegrates.
(3) Simply saying "x random event could happen given enough time" is actually quite against standard scientific methods, which use statistical improbability to prove answers. It is _possible_ that the results of all the science done in the last year is just the result of randomness, but we reject that possibility because it is statistically improbable.
There were between 2-5,000,000 American Indians here when the white man arrived. Not one of them was a christian.
"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."
If evolution were correct and the 200 million years did occur, I find it hard to believe that the same form that was beneficial in that ecosystem remained beneficial for every ecosystem for the last 200 million years, with the dramatic changes that would have occurred in the populations of other animals.
Please, stick to micro-thinking. Macro-thinking is sooooo confusing.
The theory of evolution: 3 monkeys, 30 minutes.
"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.)"
One of the characteristics of such dogs is usually the great mutational load that they carry. This is indicative of the creationist model, where mutations that are carried within the population are normally bad. You can create a decrepit dog that has trouble interbreeding with genetically healthier dogs, but how does this fit within a theory of evolution that has a generally upward movement of complexity? (I know that the theory itself does not say "upward movement", but every evolutionary tree I've ever seen starts with pre-biotic material, moves towards bacteria-like organisms, then to single-celled organisms, then to multicellular life, then to more complex multicellular life, so there must be some sort of general upward direction)
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