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.”
Ya know what ....a flying reptile is still a flying reptile. There is no proof that this flying reptile turned into any kind of "bird". Same with the whale with legs. It didn't turn into a giraffe. It turned into a whale with legs. I don't see that there has been any significant variation, other than relatively superficial ones such as size, color, scales, whatever, over potentially millions of years. Even saying that this might have happened in the past, why is there no evidence of new evolving species over the past few thousand years? Surely something must have changed radically into something else by now or is this not an ongoing process?
Pakicetus 
Ambulocetus 
Rodhocetus 
Procetus
Here is an argument that I have yet to have an answer to:
Darwin formed his theory of evolution in part by observing the minute changes in the species of finches and turtles on the Galapagos (sp?) Islands and it is widely accepted that these changes were caused by the birds and turtles being separated for thousands of years and different genes becoming more or less dominant in the animals.
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?
You can't come up with enough time for it to happen.
This explains then why so-called scientists turn into dumbos.
This might be true, however, too 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. I don't know that that is true at all. For example, the pictures you just posted - there is some similarity just a one might say there is similarity between a small cat and a small dog (there are more similarities than you might initially consider once you think about it), however do cats and dogs have a common ancestor because they have some characteristics in common? I don't know. And I don't know how you go about proving such a descent either. Where is the proof other than visual similarities? What would constitute "proof" for this evolution? Personally I think scientists are as desperate to prove their belief in evolution as religious folks might be to prove it isn't true.
Are those pictures a joke? Is this an attempt at pro macro-evolution material?
That's one of the basic problems, I think. 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. Perhaps evolution is true, however, it cannot be at this incredibly slow pace. Like you, I don't think there would be enough time. What I think is that these folks are stuck in a conundrum. They don't want to believe in God and specific creation, which is fine with me, however, they must therefore come up with some explanation for the existence of creation - most importantly the creation of man. So they back into evolution which seems to be to be a theory largely based on the similiarities between one creature and another, seeming later in the fossil records. I think it's as much a belief system as creationism as unlike much of the mechanical side of science, you cannot demonstrate that it actually happened. You have to postulate based on appearances.
But they are all still whales. No change at all except for size, color, shape, fur, teeth and other such superficial things.
I'm having a hard time trying to figure out what survival benefit body armor would convey to a 3 inch fish that would normally be swallowed whole by its predators.
I don't know but I think I personally would have put the miner with the jack leg at the peak of evolution. That is one thing my Dad and I always agreed on. :-)
Absolutely - and that is the bottom line. They are still whales. A fish is just a fish...as time goes by.
do you doubt the truth of seraphims as detailed in the Bible?
Actually, it isn't the theory of evolution per se that led to those nasty little 'isms'.
It was the loss of the fear of God and adherence to His Word.
Evolution is just one more destructive manifestation of man's vain attempt to rationalize existence apart from God.
Once man throws God over the side, those who are created in His Image soon follow.
Loving your neighbor as yourself is the natural outcome of loving God.
If you don't care about the Lord, what could possibly lead you to give a rip about anybody else once the chips are down?
Do you think you can make a case that a strict adherence to Christian principles by society and by individuals would not have prevented every single one of the scourges you list in that post?
stupid, stupid, stupid, stupid, stupid, stupid
I don't care what the Bible says about seraphims. The Bible has nothing to do with what I think about evolution. What I have seen about evolution is that scientists, like creationists, have their own belief systems, one tenet of which is called evolution. Evolution is apparently based upon observing similarities in animals at different points in the fossil records and assuming that they are related or that one is "descended" from another because they share common characteristics or appearance. This is not proof of anything. In fact, it is as considerable an exercise in imagination as that of the creation of seraphim.
I don't know what the truth is. But I don't assume anything when it comes to the things of this earth.
***stupid, stupid, stupid, stupid, stupid, stupid***
Don't be so hard on yourself bub. We all make mistakes.
from soliton to soliton, stop trying to cast your pearls before swine. DO NOT argue with the Flat Earth society.
Good Bye! I speak no more to fools.
Yeah, you're obviously too smart for us. Maybe if you keep staring at those pearls long enough, they'll evolve into a necklace.
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